The sebaceous glands are microscopic glands in the skin that secrete an oily/ waxy matter, called sebum, to lubricate the skin and hair of mammals.[1] In humans, they are found in greatest abundance on the face and scalp, though they are distributed throughout all skin sites except the palms and soles.[2] In the eyelids, meibomian sebaceous glands secrete a special type of sebum into tears.
There are several related medical
conditions, including acne, sebaceous cysts, hyperplasia, sebaceous adenoma and sebaceous gland carcinoma (see section below: Pathology). Locations and morphology A branched type of acinar gland, the sebaceous glands exist in humans
throughout the skin except in the palms of the hands and soles of the feet. Sebaceous glands can usually be found in
hair-covered areas, where they are
connected to hair follicles (see image at top). The glands deposit sebum on the
hairs, and bring it to the skin surface along
the hair shaft. The structure consisting of
hair, hair follicle, arrector pili muscle, and sebaceous gland is known as a pilosebaceous unit. Sebaceous glands are also found in non-
haired areas (glabrous skin) of eyelids, nose, penis, labia minora and nipples. Here, the sebum traverses ducts that terminate
in sweat pores on the surface of the skin.[citation needed] At the rim of the eyelids, meibomian glands are a specialized form of sebaceous gland. They secrete a form of sebum (called meibum) onto the eye, slowing the evaporation of tears. Sebum Sebaceous glands secrete the oily, waxy
substance called sebum (Latin, meaning fat or tallow) that is made of fat (lipids), wax, and the debris of dead fat-producing cells. [3] In the glands, sebum is produced within specialized cells and is released as these cells burst; sebaceous glands are thus
classified as holocrine glands. Seborrhoea is the name for the condition of greasy skin caused by excess sebum.[4] Sebum is odorless, but its bacterial breakdown can produce odors. Sebum is
the cause of some people's experiencing "oily" hair,[5] as in hot weather or if not washed for several days. Earwax is partly composed of sebum. Function Although it is commonly believed that
sebum acts to protect and waterproof hair
and skin, scientists have contended that
"low levels of sebaceous gland activity are
not correlated with dry skin" and it may
serve little or no purpose in modern humans.[6][7] Composition The composition of sebum varies across
species. In humans, the lipid content is as follows:[8] Percent composition Substance 25% wax monoesters 41% triglycerides 16% free fatty acids 12% squalene Sapienic acid is a sebum fatty acid that is unique to humans. Control The following treatments have been
shown to reduce sebum secretion rates: Isotretinoin[9] SMT D002[10] Spironolactone[11] (suitable for females only) Changes during development The sebaceous glands of a human fetus in utero secrete a substance called Vernix caseosa, a "waxy" or "cheesy" white substance coating the skin of newborns. The activity of the sebaceous glands
increases during puberty because of heightened levels of androgens. In males, sebaceous glands begin to appear
predominantly on the penis, on the shaft and around the rim of the penile head
during and after puberty. This is however
normal, not to be confused with an STD. In females, they appear predominantly in the labia minora. Pathology Sebaceous glands are involved in skin
problems such as acne and keratosis pilaris. In the skin pores, sebum and keratin can create a hyperkeratotic plug called a
"microcomedone". The prescription drug isotretinoin significantly reduces the amount of sebum produced by the
sebaceous glands, and is used to treat acne. The extreme use (up to 10 times doctor-
prescribed amounts) of anabolic steroids by bodybuilders, for muscle gain can cause acne. The sebaceous gland is stimulated
due to some steroids conversion into
dihydrotestosterone. This may cause
serious acne on the face, neck, chest, back
and shoulders. A blocked sebaceous gland can result in a sebaceous cyst. A condition involving enlarged sebaceous
glands is known as sebaceous hyperplasia. Sebaceous gland carcinoma is a rare and aggressive form of cancer involving the sebaceous glands; sebaceous adenoma is a more benign neoplasm of the sebaceous glands. Sebum can also build up around body piercings.[12] Importance to other animals Demodex mite Certain species of Demodex mites feed on sebum and are commonly found in the
sebaceous glands of mammals, including
those of humans. The preputial glands of mice and rats are large modified sebaceous glands that
produce pheromones.
The sebaceous glands are microscopic glands in the skin that secrete an oily/ waxy matter, called sebum, to lubricate the skin and hair of mammals.[1] In humans, they are found in greatest abundance on the face and scalp, though they are distributed throughout all skin sites except the palms and soles.[2] In the eyelids, meibomian sebaceous glands secrete a special type of sebum into tears.
There are several related medical
conditions, including acne, sebaceous cysts, hyperplasia, sebaceous adenoma and sebaceous gland carcinoma (see section below: Pathology). Locations and morphology A branched type of acinar gland, the sebaceous glands exist in humans
throughout the skin except in the palms of the hands and soles of the feet. Sebaceous glands can usually be found in
hair-covered areas, where they are
connected to hair follicles (see image at top). The glands deposit sebum on the
hairs, and bring it to the skin surface along
the hair shaft. The structure consisting of
hair, hair follicle, arrector pili muscle, and sebaceous gland is known as a pilosebaceous unit. Sebaceous glands are also found in non-
haired areas (glabrous skin) of eyelids, nose, penis, labia minora and nipples. Here, the sebum traverses ducts that terminate
in sweat pores on the surface of the skin.[citation needed] At the rim of the eyelids, meibomian glands are a specialized form of sebaceous gland. They secrete a form of sebum (called meibum) onto the eye, slowing the evaporation of tears. Sebum Sebaceous glands secrete the oily, waxy
substance called sebum (Latin, meaning fat or tallow) that is made of fat (lipids), wax, and the debris of dead fat-producing cells. [3] In the glands, sebum is produced within specialized cells and is released as these cells burst; sebaceous glands are thus
classified as holocrine glands. Seborrhoea is the name for the condition of greasy skin caused by excess sebum.[4] Sebum is odorless, but its bacterial breakdown can produce odors. Sebum is
the cause of some people's experiencing "oily" hair,[5] as in hot weather or if not washed for several days. Earwax is partly composed of sebum. Function Although it is commonly believed that
sebum acts to protect and waterproof hair
and skin, scientists have contended that
"low levels of sebaceous gland activity are
not correlated with dry skin" and it may
serve little or no purpose in modern humans.[6][7] Composition The composition of sebum varies across
species. In humans, the lipid content is as follows:[8] Percent composition Substance 25% wax monoesters 41% triglycerides 16% free fatty acids 12% squalene Sapienic acid is a sebum fatty acid that is unique to humans. Control The following treatments have been
shown to reduce sebum secretion rates: Isotretinoin[9] SMT D002[10] Spironolactone[11] (suitable for females only) Changes during development The sebaceous glands of a human fetus in utero secrete a substance called Vernix caseosa, a "waxy" or "cheesy" white substance coating the skin of newborns. The activity of the sebaceous glands
increases during puberty because of heightened levels of androgens. In males, sebaceous glands begin to appear
predominantly on the penis, on the shaft and around the rim of the penile head
during and after puberty. This is however
normal, not to be confused with an STD. In females, they appear predominantly in the labia minora. Pathology Sebaceous glands are involved in skin
problems such as acne and keratosis pilaris. In the skin pores, sebum and keratin can create a hyperkeratotic plug called a
"microcomedone". The prescription drug isotretinoin significantly reduces the amount of sebum produced by the
sebaceous glands, and is used to treat acne. The extreme use (up to 10 times doctor-
prescribed amounts) of anabolic steroids by bodybuilders, for muscle gain can cause acne. The sebaceous gland is stimulated
due to some steroids conversion into
dihydrotestosterone. This may cause
serious acne on the face, neck, chest, back
and shoulders. A blocked sebaceous gland can result in a sebaceous cyst. A condition involving enlarged sebaceous
glands is known as sebaceous hyperplasia. Sebaceous gland carcinoma is a rare and aggressive form of cancer involving the sebaceous glands; sebaceous adenoma is a more benign neoplasm of the sebaceous glands. Sebum can also build up around body piercings.[12] Importance to other animals Demodex mite Certain species of Demodex mites feed on sebum and are commonly found in the
sebaceous glands of mammals, including
those of humans. The preputial glands of mice and rats are large modified sebaceous glands that
produce pheromones.
VIRGINITY
A virgin (or maiden) originally meant a woman who has never had sexual intercourse. It is derived from the Latin virgo, which means "sexually
inexperienced woman". As in Latin, the
English word is also often used with wider
reference, by relaxing the age, gender or sexual criteria.[1] Hence, more mature women can be virgins ( The Virgin Queen), men can be virgins, and potential initiates
into many fields can be colloquially termed
virgins; for example, a skydiving "virgin".
In the latter usage, virgin simply means
uninitiated. By extension from its primary sense, the
idea that a virgin has a sexual "blank slate",[2] unchanged by any past intimate connection or experience,[2] leads to the abstraction of unadulterated purity (see below). Hence, virgin can even be used with non-human referents. Unalloyed metal is sometimes described as virgin.[1] Some cocktails can be described as virgin, when lacking the alcoholic admixture.[1] Similarly, olive oil may be called virgin if it
contains no refined oil and has an appropriate acidity.[3] Unfertilized gametes and computer systems can be virgin.[1] Females of various species, by analogy with Homo sapiens, if they have never mated, can also be called virgin. [1] The loss of virginity may call to mind the
end of innocence, and the beginning of
sexual maturity. In this association "virgin"
often references the first instance of a
potentially extended series of like events.
Just as extra-virgin olive oil is from the first pressing, so a maiden or virgin speech is an incumbent's first address. The same metaphor, using the synonym maiden, is
applied to the first or maiden voyage of a ship. In cricket, a maiden over is an over from which no runs were scored. Maiden castles are those with the reputation of never having been captured. Chastity does not imply virginity. Chastity derives from the Latin castitas, meaning
"cleanliness" or "purity"—and does not
necessarily mean the renunciation of all
sexual relations, but rather the temperate
sexual behavior of legitimately married
spouses, for the purpose of procreation, or the sexual continence of the unmarried.[4] Etymology The word virgin comes via Old French virgine from the root form of Latin virgo, genitive virgin-is, meaning literally "maiden" or "virgin"—a sexually intact young woman. [5] The Latin word probably arose by analogy with a suit of lexemes based on vireo, meaning "to be green,
fresh or flourishing", mostly with botanic reference—in particular, virga meaning "strip of wood".[6] The first known use of virgin in English comes from an Anglo- Saxon manuscript held at Trinity College, Cambridge. c. 1200: Ðar haueð ... martirs, and confessors, and uirgines maked faier bode inne to women. — Trinity College Homilies 185 [ms B.15.34 (369)] In this, and many later contexts, the
reference is specifically Christian, alluding to members of the Ordo Virginum known
to have existed since the early church from the writings of the Church Fathers.[7] However, within about a century, the
word was expanded to apply also to Mary, the mother of Jesus, hence to sexual virginity explicitly. c. 1300: Conceiud o þe hali gast, born o þe virgine marie. — Cursor Mundi 24977 Further expansion of the word to include
virtuous (or naïve) young women,
irrespective of religious connection,
occurred over about another century. c. 1400: Voide & vacand of vices as virgyns it ware. — The Wars of Alexander 4665 These are just three of the eighteen
definitions of virgin from the first edition
of the Oxford English Dictionary (OED1, pages 230-232). Most of the OED1
definitions, however, are very similar. Frank Harris (1923) claims to have given the following humorous etymology in a
lecture, " 'vir,' as everyone knows, is Latin
for a man, while 'gin' is good old English
for a trap; virgin is therefore a mantrap."[8] Other, serious, but unsupported etymologies exist in print. The German word for "virgin" is Jungfrau. Jungfrau literally means "young woman",
but is not used in this sense. Instead "junge
Frau" can be used. The rather dated
German word for a young (unmarried)
woman, without implications regarding
sexuality, is Fräulein. Fräulein was used in German as a title of respect, equivalent to
current usage of Miss in English. Jungfrau is the word reserved specifically for sexual
inexperience. As Frau means "woman", it suggests a female referent. Unlike English,
German also has a specific word for a male
virgin Jüngling ("Youngling"). It is, however, dated too and rarely used.
Jungfrau, with some masculine modifier, is
more typical, as evidenced by the film, The 40-Year-Old Virgin , about a 40 year-old male virgin, titled in German, "Jungfrau (40), männlich, sucht…".[9] Note that the term used for the starsign virgo also is Jungfrau, which makes the above movie
title ambiguous. German also distinguishes
between young women and girls, who are denoted by the word Mädchen. The English cognate "maid" was often used to imply virginity, especially in poetry. German is not the only language to have a
specific name for male virginity; in French,
male virgins are called "puceau" or "Joseph"[citation needed] whereas a number of indigenous Bolivians, males
presenting with phimosis who injure their frenulum during first penetration are said to be "uncartridged" as opposed to "cartridged" before first intercourse.[10] By contrast, the Greek word for "virgin" is
parthenos (παρθένος, see Parthenon). Although typically applied to women, like
English, it is also applied to men, in both
cases specifically denoting absence of
sexual experience. When used of men, it
does not carry a strong association of
"never-married" status. However, in reference to women, historically, it was
sometimes used to refer to an engaged
woman—parthenos autou (παρθένος
αὐτού, his virgin) = his fiancée as opposed to gunē autou (γυνή αὐτού, his woman) =
his wife. This distinction is necessary due
to there being no specific word for wife (or
husband) in Greek. In culture In a cross-cultural study, At what age do
women and men have their first sexual
intercourse? (2003) Michael Bozon of the
French Institut national d'études démographiques found that contemporary cultures to fall into three broad categories. [11] In the first group, the data indicated
families arranging marriage for daughters
as close to puberty as possible with
significantly older men. Age of men at
sexual initiation in these societies is at
later ages than that of women, but is often extra-marital. This group included sub- Saharan Africa (the study listed Mali, Senegal and Ethiopia). The study considered the Indian subcontinent also fell into this group, although data were only
available from Nepal. In the second group, the data indicated
families encouraged daughters to delay
marriage, and to abstain from sexual
activity prior to it. However, sons are
encouraged to gain experience with older
women or prostitutes prior to marriage. Age of men at sexual initiation in these
societies is at lower ages than that of
women. This group includes Latin cultures,
both from southern Europe (Portugal, Greece and Romania are noted) and from Latin America (Brazil, Chile, Dominican Republic). The study considered many Asian societies also fell into this group,
although matching data were only
available from Thailand. In the third group, age of men and women
at sexual initiation was more closely
matched. There were two sub-groups,
however. In non-Latin, Catholic countries
(Poland and Lithuania are mentioned), age at sexual initiation was higher, suggesting
later marriage and reciprocal valuing of
male and female virginity. The same
pattern of late marriage and reciprocal
valuing of virginity was reflected in Singapore and Sri Lanka. The study considered China and Vietnam also fell into this group, although data were not
available. Finally, in northern and eastern European
countries, age at sexual initiation was
lower, with both men and women
involved in sexual activity prior to any
union formation. The study listed Switzerland, Germany and the Czech Republic as members of this group. Consistent with the northern European
findings above, a more recent sex education survey of UK teenagers between the ages of 14 and 17 in 2008 (conducted
by YouGov for Channel 4), showed that only 6% of these teenagers intended
waiting until marriage before having sex. [12] Perceived value and "technical virginity" Female virginity is closely interwoven
with personal or even family honor in
many cultures, especially those known as shame societies, in which the loss of virginity before marriage is a matter of
deep shame. For example, among the Bantu of South Africa, virginity testing or even the suturing of the labia majora (called infibulation) has been commonplace. Traditionally, Kenuzi girls
(of the Sudan) are married before puberty [13] by adult men who inspect them manually for virginity. [14]Female circumcision is later performed at puberty to ensure chastity.[15] History evidences laws and customs that
required a man who seduced or raped a virgin to take responsibility for the
consequences of his offense by marrying
the girl or by paying compensation to her father on her behalf.[16] In some countries until the late 20th century, if a man did not
marry a woman whose virginity he had
taken, the woman was allowed to sue the
man for money, in some languages named "wreath money".[17] Emphasizing the monetary value of female
virginity, some women have offered their
virginity for sale. In 2004, a lesbian student
from the University of Bristol was said to
have sold her virginity online for £8,400,
and Londoner Rosie Reid, 18, reportedly slept with a 44-year-old BT engineer in a
Euston hotel room against payment for her virginity. [18] In 2008, Italian model Raffaella Fico, then 20 years old, offered her virginity for €1 million. [19] In that same year, an American using the
pseudonym Natalie Dylan announced she would accept bids for her virginity through a Nevada brothel's web site.[20][21] Some historians and anthropologists note that many societies before the sexual revolution that place a high value on virginity before marriage actually have a
large amount of premarital sexual activity
that does not involve vaginal penetration: for example, oral sex, anal sex and mutual masturbation. This is considered "technical" virginity, as vaginal intercourse
has not occurred but the participants are sexually active. [22][23][24][25] Since the early 1990s, the concept of "technical"
virginity has been popular among US teenagers.[24][25] Additionally, some gay males may consider oral sex "technical
virginity" in comparison to anal penetration.[26] In 1999, a study published in the Journal of the American Medical Association, which examines the definition of sex based on a 1991 random sample of
599 college students from 29 US states,
found that 60% said oral-genital contact
did not constitute having sex. "That's the
'technical virginity' thing that's going on,"
said Stephanie Sanders, associate director of the Kinsey Institute for Research in Sex, Gender and Reproduction at Indiana University. Sanders, as the co-author of the study, and along with other researchers,
titled the findings "Would You Say You 'Had Sex' If ...?"[25] In another study, published in 2001 in The Journal of Sex Research, over half of respondents considered that virginity could only be lost through having consensual sex.[27] Loss of virginity The act of losing one's virginity is
commonly considered within many
cultures to be an important life event and a rite of passage. The loss of virginity may be viewed as a milestone in a person's life. In human females, the hymen is a thin film of membrane situated just inside the vulva which can partially occlude the entrance to
the vaginal canal. It is flexible and can be stretched or torn during first engagement
in vaginal intercourse. Throughout history,
the presence of an intact hymen has been
seen by many as physical evidence of
virginity, particularly alongside "proof of
blood", virginity as proved by the presence of vaginal bleeding from intercourse
connected to the tearing of the hymen. The presence of a hymen is often
considered to be an indication of virginity,
but is no guarantee given that some
degree of sexual activity may occur
without rupturing the hymen. The lack of a
hymen is an even less clear indication of virginity lost as the hymen's shape,
thickness and coverage is extremely
variable, and one that does occlude the
entrance to the vaginal canal may be
broken through means other than sexual
activity. It is a common belief that some women simply lack a hymen, but some
doubt has been cast on this by a recent study.[28] It is likely that almost all women are born with a hymen, but not necessarily
ones that will experience a measurable
change during first experience of vaginal
intercourse. There may also exist varying definitions as
to the type and extent of sexual activity
that is considered by a person to terminate
the state of "virginity" as the definition of
virginity is problematized by some
experiences. For example, the prevailing notion of virginity as lost only through
vaginal intercourse is problematized by
homosexuality, as well as by some youth
who engage in oral or anal sex for the
purpose of retaining their vaginal virginity.
The issue is further complicated by the availability of hymenorrhaphy surgical procedures which repair or replace the
hymen, marketed to both sexually active
women to restore their "virginity", as well
as to virginal women who are concerned
that their hymens may not provide
adequate proof of their virginity through bleeding or the perceived tightness of their
vagina. In the majority of women, the hymen is
sufficiently vestigial as to pose no obstruction to the entryway of the vagina.
The presence of a broken hymen may
therefore indicate that the vagina has
been penetrated but also that it was
broken via physical activity or the use of a tampon or dildo. Many women possess such thin, fragile hymens, easily stretched and
already perforated at birth, that the hymen
can be broken in childhood without the
woman even being aware of it, often
through athletic activities. A slip while
riding a bicycle may on occasion result in the bicycle's saddle-horn entering the
introitus just far enough to break the hymen.[29] In rare cases a woman may possess an
imperforate hymen that prevents the
release of menstrual discharge. A surgical procedure known as hymenotomy, which creates an opening in the hymen, is
sometimes required to avert deleterious
health effects. The playwright Ben Jonson claimed that Queen Elizabeth I of England, the Virgin Queen, had a "membranum" that
made her "incapable of Man", and that a
friend of hers, a "chirurgeon", had offered
to remedy the problem with his scalpel and
that Elizabeth had demurred. Some studies have shown that people
continue to lose their virginity at an earlier age than previous generations.[30][31] The 2005 Durex Global sex survey reports that
people worldwide are having sex for the
first time at an average age of 17.3
(ranging from 15.6 in Iceland to 19.8 in India).[31] Cultural anthropology Cultural anthropologists have discovered that romantic love and sexual jealousy are universal features of human relationships. [32] Social values related to virginity reflect both sexual jealousy and ideals of
romantic love, and appear to be deeply
embedded in human nature.[citation needed] Social psychology Psychology explores the connection between thought and behavior. Seeking
understanding of social (or anti-social)
behaviors includes sexual behavior. Joan
Kahn and Kathryn London studied U.S.
women married between 1965 and 1985
to see if virginity at marriage influenced risk of divorce. “ This article examines the
relationship between
premarital sexual activity
and the long-term risk of
divorce among U.S. women
married between 1965 and 1985. Simple cross-
tabulations from the 1988
National Survey of Family
Growth indicate that women
who were sexually active
prior to marriage faced a considerably higher risk of
marital disruption than
women who were virgin
brides. A bivariate probit
model is employed to
examine three possible explanations for this positive
relationship: (a) a direct
causal effect, (b) an indirect
effect through intervening
"high risk" behaviors (such
as having a premarital birth or marrying at a young age),
and (c) a selectivity effect
representing prior
differences between virgins
and non-virgins (such as
family background or attitudes and values). After
a variety of observable
characteristics are
controlled, non-virgins still
face a much higher risk of
divorce than virgins. However, when the analysis
controls for unobserved
characteristics affecting both
the likelihood of having
premarital sex and the
likelihood of divorce, the differential is no longer
significant. These results
suggest that the positive
relationship between
premarital sex and the risk
of divorce can be attributed to prior unobserved
differences (e.g., the
willingness to break
traditional norms) rather
than to a direct causal effect. [33] ” This study makes no recommendation; it
simply notes that the women most likely
to exercise freedom to enter sexual
relationships prior to marriage, overlap
significantly with the women most likely
to exercise freedom to leave a relationship after marriage. Men were not the subject
of this study.
FORESKIN
In male human anatomy, the foreskin is a generally retractable double-layered fold of skin and mucous membrane that covers
the glans penis and protects the urinary meatus (pronounced /miːˈeɪtəs/) when the penis is not erect. It is also described as the prepuce, a technically broader term that also includes the clitoral hood in women, to which the foreskin is
embryonically homologous. Description Diagram of a portion of the male anatomy The outside of the foreskin is a
continuation of the skin on the shaft of the
penis, but the inner foreskin is a mucous membrane like the inside of the eyelid or the mouth. The mucocutaneous zone occurs where the outer and inner foreskin meet.
Like the eyelid, the foreskin is free to
move after it separates from the glans,
usually by puberty. Smooth muscle fibres keep it close to the glans but make it highly elastic.[1] The foreskin is attached to the glans by a frenulum, which helps return the foreskin over the glans. The presence of Meissner's corpuscles (a type of nerve ending) has been reported.
Their density is reportedly greater in the ridged band (a region of ridged mucosa at the tip of the foreskin) than in the larger area of smooth mucosa.[2] They are affected by age: their incidence decreases after adolescence.[3] In some individuals, no Meissner's corpucles could be identified. [4] In the late 1950s, Winkelmann suggested that some receptors had been
wrongly identified as Meissner's corpuscles.[5][6] According to a study by Sorrells et al.
(2007), the five most sensitive areas of the
penis are on the foreskin, and that the
glans is more sensitive in the uncircumcised penis [7] - though the study has been criticized by Waskett and Morris,
who argue that re-analysis of Sorrells' data shows no significant differences. [8] In 2009, Schober et al reported on self-
assessed sexual sensitivity in 81 men, 11 of
whom were not circumcised. When
assessing areas producing sexual pleasure,
the foreskin was ranked 7th, after the
glans, lower and upper shaft, and the left and right sides of the penis, but above the
area between scrotum and anus, the scrotum itself, and the anus.[9] Development Eight weeks after fertilization, the
foreskin begins to grow over the head of
the penis, covering it completely by 16
weeks. At this stage, the foreskin and
glans share an epithelium (mucous layer) that fuses the two together. It remains this
way until the foreskin separates from the glans.[10] At birth, the foreskin is usually still fused with the glans.[10] As childhood progresses the foreskin and the glans gradually
separate, a process that may not be complete until late puberty.[11] Thorvaldsen and Meyhoff (2005) reported
that average age of first foreskin retraction in Denmark is 10.4 years.[12] Wright (1994) argues that forcible
retraction of the foreskin should be
avoided and that the child himself should
be the first one to retract his own foreskin. [13] Attempts to forcibly retract it can be painful and may injure the foreskin. [14] In children, the foreskin usually covers the
glans completely but in adults, this need not be so. Schöberlein (1966) [15] found that about 50% of young men had full
coverage of the glans, 42% had partial
coverage, and, in the remaining 8%, the
glans was uncovered. After adjusting for circumcision, he stated that, in 4% of the young men, the foreskin had
spontaneously atrophied (shrunk). There is
considerable variation in the degree to
which the foreskin retracts during erection; in some adults the foreskin remains
covering the glans until retracted by sexual
activity. Functions The foreskin typically covers the glans when the penis is flaccid (left), but generally retracts upon erection (right) The World Health Organization state that there is "debate about the role of the
foreskin, with possible functions including
keeping the glans moist, protecting the
developing penis in utero, or enhancing
sexual pleasure due to the presence of nerve receptors".[16] Sexual For more details on this topic, see Sexual effects of circumcision. Taylor et al. (1996) described the foreskin
in detail, documenting a ridged band of
mucosal tissue. They stated: "This ridged
band contains more Meissner's corpuscles
than does the smooth mucosa and exhibits features of specialized sensory mucosa." [2] In 1999, Cold and Taylor stated: "The
prepuce is primary, erogenous tissue necessary for normal sexual function." [17] Boyle et al. (2002) state that "the complex
innervation of the foreskin and frenulum
has been well documented, and the
genitally intact male has thousands of fine
touch receptors and other highly erogenous
nerve endings—many of which are lost to circumcision, with an inevitable reduction
in sexual sensation experienced by circumcised males."[18] The AAP noted that the work of Taylor et al. (1996) "suggests
that there may be a concentration of
specialized sensory cells in specific ridged areas of the foreskin."[19] Moses and Bailey (1998) describe the
evidence of sensory function as "indirect,"
and state that, "aside from anecdotal
reports, it has not been demonstrated that
this is associated with increased male sexual pleasure."[20] The World Health Organization (2007) states that there is
little evidence for diminished sexual
function, adding that studies have been inconsistent.[21] Fink et al. (2002) reported "[a]lthough many have speculated about
the effect of a foreskin on sexual function,
the current state of knowledge is based on
anecdote rather than scientific evidence."[22] Masood et al. (2005) state that "[c]urrently no consensus exists about
the role of the foreskin or the effect
circumcision has on penile sensitivity and overall sexual satisfaction."[23] Schoen (2007) states that "[a]necdotally, some
have claimed that the foreskin is important
for normal sexual activity and improves
sexual sensitivity. Objective published
studies over the past decade have shown
no substantial difference in sexual function between circumcised and uncircumcised men."[24] The term 'gliding action' is used in some
papers to describe the way the foreskin
moves during sexual intercourse. This
mechanism was described by
Lakshamanan & Prakash in 1980, stating
that "[t]he outer layer of the prepuce in common with the skin of the shaft of the
penis glides freely in a to and fro fashion..."[25] Several people have argued that the gliding movement of the foreskin is important during sexual intercourse.[26] Warren & Bigelow (1994) state that gliding
action would help to reduce the effects of
vaginal dryness and that restoration of the
gliding action is an important advantage of foreskin restoration.[27]O'Hara (2002) describes the gliding action, stating that it
reduces friction during sexual intercourse, and suggesting that it adds "immeasurably
to the comfort and pleasure of both parties".[28] Taylor (2000) suggests that the gliding action, where it occurs, may
stimulate the nerves of the ridged band, [29] and speculates (2003) that the stretching of the frenulum by the rearward
gliding action during penetration triggers ejaculation.[30] Whiddon (1953), Foley (1966), and Morgan
(1967) all believed that the presence of the
foreskin made sexual penetration easier. [31][32][33] Other Gairdner (1949) states that the foreskin protects the glans[10] but some studies show that inflammation of the glans is
more common when the foreskin is present.[34] In contrast, meatitis, meatal ulcer, and meatal stenosis are thought to be less common.[35][36][37] The fold of the prepuce maintains sub-
preputial wetness, which mixes with
exfoliated skin to form smegma. Some authors believe that smegma contains antibacterial enzymes,[38] though their theory has been challenged.[39] The American Academy of Pediatrics (1999) state that "no controlled scientific data are
available regarding differing immune
function in a penis with or without a foreskin."[40] Inferior hygiene has been associated with balanitis,[41] though excessive washing can cause non-specific dermatitis.[42] Evolution In primates, the foreskin is present in the
genitalia of both sexes and likely has been
present for millions of years of evolution. [43] The evolution of complex penile morphologies like the foreskin may have been influenced by females. [44][45][46] It has been proposed that the foreskin evolved to facilitate masturbation. [47] Conditions Frenulum breve is a frenulum that is insufficiently long to allow the foreskin to
fully retract, which may lead to discomfort
during intercourse. Phimosis is a condition where the foreskin of an adult cannot be
retracted properly. Before adulthood, the
foreskin may still be separating from the glans.[48] Phimosis can be treated by gently stretching the foreskin, by changing masturbation habits,[49] using topical steroid ointments, preputioplasty, or by the more radical option of circumcision. Posthitis is an inflammation of the foreskin. A condition called paraphimosis may occur if a tight foreskin becomes trapped behind
the glans and swells as a restrictive ring.
This can cut off the blood supply, resulting
in ischaemia of the glans penis. Aposthia is a rare condition in which the foreskin is not present at birth. Surgical and other modifications of the
foreskin Circumcision is the removal of the foreskin, either partially or completely. It may be
done for religious requirements, health
reasons such as to treat a medical disorder,
or personal preferences surrounding
hygiene and aesthetics. Preputioplasty is a minor procedure designed to relieve a tight
foreskin without resorting to circumcision. Foreskin restoration techniques (developed to help circumcised men 'regrow' a skin
covering for the glans by tissue expansion) can be used by men with short foreskins to
lengthen the natural foreskin so that it
covers the glans. A narrow foreskin may also be widened by tissue expansion. [50] Other practices include genital piercings
involving the foreskin and slitting the foreskin.[51] Langerhans cells Langerhans cells are immature dendritic cells that are found in all areas of the penile epithelium,[52] but are most superficial in the inner surface of the foreskin.[52] A study by Szabo and Short (2000) targets Langerhans cells as
receptors of HIV, and states that these cells
"must be regarded as the most probable
sites for viral entry in primary HIV infection in men."[53] Langerhans cells are also known to express the c-type lectin
langerin, which may play a role in
transmission of HIV to nearby lymph nodes.[52] However, de Witte et al. (2007) reported that langerin, produced by
Langerhans cells, blocks the transmission of HIV to T cells.[54] Foreskin-based medical and consumer
products Foreskins obtained from circumcision
procedures are frequently used by
biochemical and micro-anatomical
researchers to study the structure and
proteins of human skin. In particular,
foreskins obtained from newborns have been found to be useful in the manufacturing of more human skin.[55] Human growth factors derived from newborns' foreskins are used to make a
commercial anti-wrinkle skin cream, TNS Recovery Complex. [56] Foreskins of babies are also used for skin graft tissue,[57][58][59] and for β- interferon-based drugs.[60] Foreskin fibroblasts have been used in biomedical research.[61] Foreskin in non-human species In koalas, the foreskin contains naturally- occurring bacteria that play an important role in fertilization.[62] Almost all mammal penises have foreskins, although in non-
human cases the foreskin is usually a
sheath into which the whole penis is
retracted. Only monotremes (the platypus and the echidna) lack foreskins.
PREPUCE
Prepuce may refer to: The foreskin, which surrounds and protects the head of the penis The clitoral hood, which surrounds and protects the head of the clitoris
FRENULUM
The Frenulum clitoridis (also known as the Crus glandis clitoridis) is a frenulum on the under-surface of the clitoral glans, created by the two medial parts of the labia minora.
ANUS
The anus is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, unwanted semi-solid matter produced during digestion, which,
depending on the type of animal, may be
one or more of: matter which the animal cannot digest, such as bones;[1] food material after all the nutrients have been
extracted, for example cellulose or lignin; ingested matter which would be toxic if it
remained in the digestive tract; and dead
or excess gut bacteria and other endosymbionts. Amphibians, reptiles, and birds use the same orifice for excreting liquid and solid
wastes, and for copulation and egg-laying; this orifice is known as the cloaca. Monotreme mammals also have a cloaca, which is thought to be a feature inherited
from the earliest amniotes via the therapsids. Marsupials have two nether orifices: one for excreting both solids and
liquids; the other for reproduction, which
appears as a vagina in females and a penis in males. Female placental mammals have completely separate orifices for defecation, urination, and reproduction; males have one opening for defecation and
another for both urination and
reproduction, although the channels
flowing to that orifice are almost
completely separate. The development of the anus was an
important stage in the evolution of multicellular animals. In fact it appears to have happened at least twice, following
different paths in protostomes and deuterostomes. This accompanied or facilitated other important evolutionary
developments: the bilaterian body plan; the coelom, an internal cavity that provided space for a circulatory system and, in some animals, formed a hydrostatic skeleton which enables worm-like animals to burrow; metamerism, in which the body was built of repeated "modules" which
could later specialize, for example the
heads of most arthropods are composed of fused, specialized segments. Etymology First attested in 1658, from Latin anus
(“ring, anus”), from Proto-Indo-European
*ano- (“ring”). See also anal, annular,
annelid. Development Main articles: protostome and deuterostome In animals at least as complex as an earthworm, the embryo forms a dent on one side, the blastopore, which deepens to become the archenteron, the first phase in the growth of the gut. In deuterostomes, the original dent becomes the anus while
the gut eventually tunnels through to make
another opening, which forms the mouth.
The protostomes were so named because it used to be thought that in their embryos
the dent formed the mouth while the anus
was formed later, at the opening made by
the other end of the gut. More recent
research, however, shows that in
protostomes the edges of the dent close up in the middle, leaving openings at the ends which become the mouth and anus.
PEA
A pea is most commonly the small spherical seed or the seed-pod of the pod fruit Pisum sativum.[1] Each pod contains several peas. Peapods are botanically a fruit,[2] since they contain seeds developed from the ovary of a (pea) flower. However,
peas are considered to be a vegetable in cooking. The name is also used to describe
other edible seeds from the Fabaceae such as the pigeon pea (Cajanus cajan), the cowpea (Vigna unguiculata), and the seeds from several species of Lathyrus. P. sativum is an annual plant, with a life cycle of one year. It is a cool season crop grown in many parts of the world; planting
can take place from winter to early
summer depending on location. The
average pea weighs between 0.1 and 0.36 grams.[3] The species is used as a vegetable, fresh, frozen or canned, and is
also grown to produce dry peas like the split pea. These varieties are typically called field peas. The wild pea is restricted to the
Mediterranean basin and the Near East. The
earliest archaeological finds of peas come
from Neolithic Syria, Turkey and Jordan. In
Egypt, early finds date from ca. 4800–
4400 BC in the Nile delta area, and from ca. 3800–3600 BC in Upper Egypt. The pea was
also present in Georgia in the 5th millennium BC. Farther east, the finds are
younger. Peas were present in Afghanistan ca. 2000 BC, in Harappa, Pakistan, and in northwest India in 2250–1750 BC. In the second half of the 2nd millennium BC this
pulse crop appears in the Gangetic basin and southern India.[4] Description The pea is a most commonly green, occasionally purple[5] or golden yellow, [6] pod-shaped vegetable, widely grown as a
cool season vegetable crop. The seeds may
be planted as soon as the soil temperature
reaches 10 °C (50 °F), with the plants
growing best at temperatures of 13 to 18
°C (55 to 64 °F). They do not thrive in the summer heat of warmer temperate and
lowland tropical climates but do grow well in cooler high altitude tropical areas. Many
cultivars reach maturity about 60 days
after planting. Worldwide pea yield Raw Green Pea Nutritional value per 100 g (3.5 oz) Energy 339 kJ (81 kcal) Carbohydrates 14.5 g - Sugars 5.7 g - Dietary fibre 5.1 g Fat 0.4 g Protein 5.4 g Vitamin A equiv. 38 μg (5%) - beta-carotene 449 μg (4%) - lutein and zeaxanthin 2593 μg Thiamine (vit. B1) 0.3 mg (26%) Riboflavin (vit. B 2) 0.1 mg (8%) Niacin (vit. B3) 2.1 mg (14%) Pantothenic acid (B5) 0.1 mg (2%) Vitamin B6 0.2 mg (15%) Folate (vit. B9) 65 μg (16%) Vitamin C 40.0 mg (48%) Calcium 25.0 mg (3%) Iron 1.5 mg (12%) Magnesium 33.0 mg (9%) Phosphorus 108 mg (15%) Potassium 244 mg (5%) Zinc 1.2 mg (13%) Percentages are relative to US recommendations for adults. Source: USDA Nutrient Database Peas have both low-growing and vining cultivars. The vining cultivars grow thin tendrils from leaves that coil around any available support and can climb to be 1–
2 m high. A traditional approach to
supporting climbing peas is to thrust
branches pruned from trees or other woody plants upright into the soil,
providing a lattice for the peas to climb.
Branches used in this fashion are
sometimes called pea brush. Metal fences, twine, or netting supported by a frame are
used for the same purpose. In dense
plantings, peas give each other some
measure of mutual support. Pea plants can self-pollinate.[7] Varieties There are many varieties of garden pea.
Some of the most common include the
following: Alaska, 55 days (smooth seeded) Thomas Laxton/Laxton's Progress/
Progress #9, 60-65 days Mr. Big, 60 days, 2000 AAS winner Little Marvel, 63 days, 1934 AAS winner Early Perfection, 65 days (This variety is
the foundation of many improved
varieties and crosses, including Dark-
Seeded Early Perfection and Bolero, the
latter being one of the most successful commercial varieties.)[8] Kelvedon Wonder, 65 days, 1997 RHS AGM winner Homesteader/Lincoln, 67 days
(heirloom, known as Greenfeast in AU, NZ)[9] Wando, 68 days Green Arrow, 70 days Tall Telephone/Alderman, 75 days
(heirloom, tall climber) Other variations of P. sativum include: Pisum sativum var. macrocarpon is
commonly known as the snow pea Pisum sativum var. macrocarpon ser. cv.
is known as the sugar or snap pea Both of these are eaten whole before the
pod reaches maturity and are hence also
known as mange-tout, French for "eat all". The snow pea pod is eaten flat, while in
sugar/snap peas, the pod becomes
cylindrical but is eaten while still crisp,
before the seeds inside develop. Pests and diseases Main article: List of pea diseases The pea leaf weevil (Latin: Sitona lineatus)
is an insect that damages peas and other
pod fruits. It is native to Europe, but has spread to other places such as Alberta, Canada. They are about 3.5 millimetres (0.14 in)—5.5 millimetres (0.22 in) long
and are distinguishable by three light-
coloured stripes running length-wise down
the thorax. The weevil larvae feed on the root nodules of pea plants, which are essential to the plant's supply of nitrogen, and thus diminish leaf and stem growth.
Adult weevils feed on the leaves and
create a notched "c-shaped" appearance on the outside of the leaves.[10] Use Culinary useFrozen green peas In early times, peas were grown mostly for
their dry seeds. In modern times, however,
peas are usually boiled or steamed, which breaks down the cell walls and makes the
taste sweeter and the nutrients more bio-
available. Along with broad beans and lentils, these formed an important part of the diet of most people in the Middle East,
North Africa and Europe during the Middle Ages.[11] By the 17th and 18th centuries it had become popular to eat peas "green",
that is, while they are immature and right
after they are picked. This was especially
true in France and England, where the
eating of green peas was said to be "both a fashion and a madness".[12] New cultivars of peas were developed by the
English during this time which became
known as garden peas and English peas. The popularity of green peas spread to North America. Thomas Jefferson grew more than 30 cultivars of peas on his estate.[13] With the invention of canning and freezing of foods, green peas became
available year-round, and not just in the
spring as before. Peas in fried rice Fresh peas are often eaten boiled and
flavored with butter and/or spearmint as a side dish vegetable. Salt and pepper are
also commonly added to peas when
served. Fresh peas are also used in pot
pies, salads and casseroles. Pod peas
(particularly sweet cultivars called mange tout and sugar peas, or the flatter "snow peas," called hé lán dòu, 荷兰豆 in Chinese) are used in stir-fried dishes, particularly those in American Chinese cuisine.[14] Pea pods do not keep well once picked, and if
not used quickly are best preserved by
drying, canning or freezing within a few hours of harvest. In India, fresh peas are used in various dishes such as aloo matar (curried potatoes
with peas) or matar paneer (paneer cheese with peas), though they can be substituted
with frozen peas as well. Peas are also
eaten raw, as they are sweet when fresh
off the bush. Split peas are also used to
make dhal, particularly in Guyana, and Trinidad, where there is a significant population of Indians. Dry, yellow split peas Dried peas are often made into a soup or simply eaten on their own. In Japan, China, Taiwan and some Southeast Asian countries, including Thailand and Malaysia, peas are roasted and salted, and eaten as snacks. In the UK, dried yellow split peas are used to make pease pudding (or "pease porridge"), a traditional dish. In North
America, a similarly traditional dish is split pea soup. Pea soup is eaten in many other parts of the world, including northern Europe, parts of middle Europe, Russia, Iran, Iraq and India.[15] In Sweden it is called ärtsoppa, and is eaten as a traditional Swedish food which predates the Viking era. This food was made from a fast-growing pea that
would mature in a short growing season.
Ärtsoppa was especially popular among
the many poor who traditionally only had
one pot and everything was cooked
together for a dinner using a tripod to hold the pot over the fire. In Chinese cuisine, pea sprouts (豆苗; dòu miáo) are commonly used in stir-fries. Pea
leaves are often considered a delicacy as
well. In Greece, Turkey, Cyprus, and other parts of the Mediterranean, peas are made into a
stew with meat and potatoes. In Hungary and Serbia, pea soup is often served with dumplings and spiced with hot paprika. In the United Kingdom, dried, rehydrated and mashed marrowfat peas, known by the public as mushy peas, are popular, originally in the north of England but now
ubiquitously, and especially as an
accompaniment to fish and chips or meat pies, particularly in fish and chip shops. Sodium bicarbonate is sometimes added to soften the peas. In 2005, a poll of 2,000
people revealed the pea to be Britain's 7th favorite culinary vegetable. [16] Processed peas are mature peas which have been dried, soaked and then heat
treated (processed) to prevent spoilage—
in the same manner as pasteurising.
Cooked peas are sometimes sold dried and
coated with wasabi, salt, or other spices. Bioplastics Bioplastics can be made using pea starch. Nutritional value Peas are high in fiber, protein, vitamins, minerals, and lutein. Dry weight is about one-quarter protein and one-quarter sugar. [17] Pea seed peptide fractions have less ability to scavenge free radicals than glutathione, but greater ability to chelate metals and inhibit linoleic acid oxidation. [18] Peas in sciencePea flowers In the mid-19th century, Austrian scientist Gregor Mendel's observations of pea pods led to the principles of Mendelian genetics, the foundation of modern genetics.[19] Peas in medicine Some people are allergic to peas, as well as lentils.[20] Etymology According to etymologists, the term pea was taken from the Latin pisum, which is the latinisation of the Greek πίσον (pison), neut. of πίσος (pisos), "pea".[21][22] It was adopted into English as the noun pease (plural peasen), as in pease pudding. However, by analogy with other plurals
ending in -s, speakers began construing
pease as a plural and constructing the singular form by dropping the "s", giving
the term "pea". This process is known as back-formation. The name marrowfat pea for mature dried
peas is recorded by the Oxford English Dictionary as early as 1733. The fact that an export cultivar popular in Japan is called
Maro has led some people to assume
mistakenly that the English name
marrowfat is derived from Japanese.
MUCUS MEMBRANE
The mucous membranes (or mucosae; singular mucosa) are linings of mostly endodermal origin, covered in epithelium, which are involved in absorption and secretion. They line cavities that are exposed to the external environment and
internal organs. They are at several places contiguous with skin: at the nostrils, the mouth, the lips, the eyelids, the ears, the genital area, and the anus. The sticky, thick fluid secreted by the mucous membranes
and glands is termed mucus. The term mucous membrane refers to where they
are found in the body and not every mucous membrane secretes mucus. The glans clitoridis, glans penis (head of the penis), along with the inside of the prepuce (foreskin) and the clitoral hood, are mucous membranes. The urethra is also a mucous membrane. The secreted mucus
traps the pathogens in the body,
preventing any further activities of
diseases. Some examples of mucosa Buccal mucosa Esophageal mucosa Gastric mucosa Intestinal mucosa Nasal mucosa Olfactory mucosa Oral mucosa Bronchial mucosa Uterine mucosa Endometrium is the mucosa of the uterus Penile mucosa
SKENES GLANDS
In human anatomy (female), the Skene's glands (also known as the lesser vestibular glands, periurethral glands, skene glands, paraurethral glands, [1]female prostate) are glands located on the anterior wall of the vagina, around the lower end of the urethra. They drain into the urethra and near the urethral opening
and may be near or a part of the G-Spot. These glands are surrounded with tissue,
which includes the part of the clitoris that reaches up inside the vagina and swells
with blood during sexual arousal. Homology and possible functions Female ejaculation Main article: Female ejaculation The location of the Skene's gland is the
general area of the vulva , glands located on the anterior wall of the vagina around the lower end of the urethra. Some[who?] believe that the Skene's glands are the source of female ejaculation.[2] In 2002, Emanuele Jannini of L'Aquila University in Italy showed that there may be an
explanation both for the phenomenon and
for the frequent denials of its existence.
Skene's glands have highly variable
anatomy, and in some extreme cases they
appear to be absent entirely. If Skene's glands are the cause of female ejaculation
and G-Spot-orgasms, this may explain the absence in many women. [3][4] It has been demonstrated that a large
amount of lubricating fluid (filtered blood plasma[specify]) can be secreted from this gland when stimulated from inside the vagina.[5] Some reports indicate that embarrassment regarding female
ejaculation, and the mistaken notion that
the substance is urine, can lead to
purposeful suppression of sexual climax,
leading women to seek medical advice and
even undergo surgery to "stop the urine". [6] Female prostate See also: G-Spot#Female prostate The Skene's glands are homologous with the prostate gland in males.[7] The fluid that emerges during sex, female ejaculation, has a composition somewhat similar to the fluid generated in males by the prostate gland,[8][9] containing biochemical markers of sexual function like human urinary protein 1[10] and the enzyme PDE5 where women without the gland had lower concentrations.[11] When examined with electron microscopy, both
glands show similar secretory structures, [12] and both act similarly in terms of prostate-specific antigen and prostate- specific acid phosphatase studies.[13][14] [15][16] Because they are increasingly perceived as merely different versions of
the same gland, some researchers are
moving away from the name Skene's gland
and are referring to it instead as the female prostate.[17] Eponym The glands were named after the physician who described them first in Western medical literature, Alexander Skene.[18] [19] Disorders Disorders of or related to the Skene's gland
include: Infection (skenitis)[20][21] Skene's duct cyst
BARTHOLINS GLANDS
The Bartholin's glands (also called Bartholin glands or greater vestibular glands) are two glands located slightly below and to the left and right of the
opening of the vagina. They secrete mucus to lubricate the vagina and are homologous to bulbourethral glands in males. However, while Bartholin's glands are located in the superficial perineal pouch in females, bulbourethral glands are located in the deep perineal pouch in males. Function They secrete mucus to provide vaginal lubrication.[2][3] Bartholin's glands secrete relatively minute amounts (one or two
drops) of fluid when a woman is sexually aroused.[4] The minute droplets of fluid were once believed to be important for
lubricating the vagina, but research from Masters and Johnson demonstrated that vaginal lubrication comes from deeper within the vagina. [4] The fluid may slightly moisten the labial opening of the vagina,
serving to make contact with this sensitive area more comfortable for the woman. [4] Pathology Although unusual, it is possible for the
Bartholin's glands to become irritated or infected, resulting in pain.[4] If the duct becomes obstructed, a Bartholin's cyst can develop, and a Bartholin's cyst in turn can
become infected and form an abscess. Carcinoma of the gland is rare, but benign tumors and hyperplasia are even more rare.[5] Eponym Bartholin's glands were first described in
the 17th century by the Danish anatomist Caspar Bartholin the Younger (1655–1738). [6] Some sources mistakenly ascribe their discovery to his grandfather, theologian
and anatomist Caspar Bartholin the Elder (1585–1629).
SEBACEOUS GLANDS
The sebaceous glands are microscopic glands in the skin that secrete an oily/ waxy matter, called sebum, to lubricate the skin and hair of mammals.[1] In humans, they are found in greatest abundance on the face and scalp, though they are distributed throughout all skin sites except the palms and soles.[2] In the eyelids, meibomian sebaceous glands secrete a special type of sebum into tears.
There are several related medical
conditions, including acne, sebaceous cysts, hyperplasia, sebaceous adenoma and sebaceous gland carcinoma (see section below: Pathology). Locations and morphology A branched type of acinar gland, the sebaceous glands exist in humans
throughout the skin except in the palms of the hands and soles of the feet. Sebaceous glands can usually be found in
hair-covered areas, where they are
connected to hair follicles (see image at top). The glands deposit sebum on the
hairs, and bring it to the skin surface along
the hair shaft. The structure consisting of
hair, hair follicle, arrector pili muscle, and sebaceous gland is known as a pilosebaceous unit. Sebaceous glands are also found in non-
haired areas (glabrous skin) of eyelids, nose, penis, labia minora and nipples. Here, the sebum traverses ducts that terminate
in sweat pores on the surface of the skin.[citation needed] At the rim of the eyelids, meibomian glands are a specialized form of sebaceous gland. They secrete a form of sebum (called meibum) onto the eye, slowing the evaporation of tears. Sebum Sebaceous glands secrete the oily, waxy
substance called sebum (Latin, meaning fat or tallow) that is made of fat (lipids), wax, and the debris of dead fat-producing cells. [3] In the glands, sebum is produced within specialized cells and is released as these cells burst; sebaceous glands are thus
classified as holocrine glands. Seborrhoea is the name for the condition of greasy skin caused by excess sebum.[4] Sebum is odorless, but its bacterial breakdown can produce odors. Sebum is
the cause of some people's experiencing "oily" hair,[5] as in hot weather or if not washed for several days. Earwax is partly composed of sebum. Function Although it is commonly believed that
sebum acts to protect and waterproof hair
and skin, scientists have contended that
"low levels of sebaceous gland activity are
not correlated with dry skin" and it may
serve little or no purpose in modern humans.[6][7] Composition The composition of sebum varies across
species. In humans, the lipid content is as follows:[8] Percent composition Substance 25% wax monoesters 41% triglycerides 16% free fatty acids 12% squalene Sapienic acid is a sebum fatty acid that is unique to humans. Control The following treatments have been
shown to reduce sebum secretion rates: Isotretinoin[9] SMT D002[10] Spironolactone[11] (suitable for females only) Changes during development The sebaceous glands of a human fetus in utero secrete a substance called Vernix caseosa, a "waxy" or "cheesy" white substance coating the skin of newborns. The activity of the sebaceous glands
increases during puberty because of heightened levels of androgens. In males, sebaceous glands begin to appear
predominantly on the penis, on the shaft and around the rim of the penile head
during and after puberty. This is however
normal, not to be confused with an STD. In females, they appear predominantly in the labia minora. Pathology Sebaceous glands are involved in skin
problems such as acne and keratosis pilaris. In the skin pores, sebum and keratin can create a hyperkeratotic plug called a
"microcomedone". The prescription drug isotretinoin significantly reduces the amount of sebum produced by the
sebaceous glands, and is used to treat acne. The extreme use (up to 10 times doctor-
prescribed amounts) of anabolic steroids by bodybuilders, for muscle gain can cause acne. The sebaceous gland is stimulated
due to some steroids conversion into
dihydrotestosterone. This may cause
serious acne on the face, neck, chest, back
and shoulders. A blocked sebaceous gland can result in a sebaceous cyst. A condition involving enlarged sebaceous
glands is known as sebaceous hyperplasia. Sebaceous gland carcinoma is a rare and aggressive form of cancer involving the sebaceous glands; sebaceous adenoma is a more benign neoplasm of the sebaceous glands. Sebum can also build up around body piercings.[12] Importance to other animals Demodex mite Certain species of Demodex mites feed on sebum and are commonly found in the
sebaceous glands of mammals, including
those of humans. The preputial glands of mice and rats are large modified sebaceous glands that
produce pheromones.
PERINEUM
In human anatomy, the perineum (Late Latin, from Greek περίνεος - perineos[1]) is a region of the body including the perineal
body and surrounding structures. There is
some variability in how the boundaries are defined.[2] Terminology It is generally defined as the surface region
in both males and females between the pubic symphysis and the coccyx. The perineum is the region of the body inferior to the pelvic diaphragm and between the
legs. It is a diamond-shaped area on the
inferior surface of the trunk which includes the anus and, in females, the vagina.[3] Its definition varies: it can refer to only the
superficial structures in this region, or it
can be used to include both superficial and
deep structures. The term lower rabbus is
used colloquially in the UK to describe this
structure. It is an erogenous zone for both males and females. Perineal tears and episiotomy often occur in childbirth with first time deliveries, but the risk of these
injuries can be reduced by preparing the
perineum, e.g. through massage. The perineum corresponds to the outlet of the pelvis. A wide variety of slang terms are
commonly used for this area of the human
body, most commonly "gooch," or "taint,"
but they generally refer to a smaller, less
inclusive area -- just the surface skin
region between the anus and the scrotum or vaginal opening.[citation needed] The anogenital distance is a measure of the distance between the anus and the base of the penis or vagina. Studies show that the human perineum is twice as long in males as in females.[4] Measuring the anogenital distance in neonatal humans
has been suggested as a noninvasive
method to determine male feminisation and thereby predict neonatal and adult reproductive disorders.[5] Boundaries Its deep boundaries are as follows:[6] in front: the pubic arch and the arcuate ligament of the pubis behind: the tip of the coccyx on either side: the inferior rami of the pubis and ischial tuberosity, and the sacrotuberous ligament Triangles A line drawn transversely across in front of
the ischial tuberosities divides the space into two triangles: Name Location Contents Urogenital
triangle the anterior
triangle in females,
contains the vagina Anal
triangle the
posterior
triangle contains the anus Perineal fascia The terminology of the perineal fascia can be confusing, and there is some
controversy over the nomenclature. This
stems from the fact that there are two
parts to the fascia, the superficial and deep
parts, and each of these can be subdivided
into superficial and deep parts. The layers and contents are as follows,
from superficial to deep: 1) Foreskin 2) superficial perineal fascia:
Subcutaneous tissue divided into two
layers: (a) A superficial fatty layer, and
(b) Colles' fascia, a deeper, membranous layer. 3) deep perineal fascia and muscles: superficial
perineal pouch Contains superficial
perineal muscles: transversus perinei
superficialis, bulbospongiosus, ischiocavernosus inferior fascia
of urogenital diaphragm, or perineal
membrane A membranous layer of
the deep fascia. deep perineal
pouch Contains the deep
perineal muscles: transversus perinei
profundus, sphincter urethrae membranaceae superior fascia
of the
urogenital
diaphragm Considered hypothetical
by some modern
anatomists, but still
commonly used to
logically divide the
contents of the region. 4) fascia and muscles of pelvic floor (levator ani, coccygeus) Areas of the perineum The region of the perineum can be
considered a distinct area from pelvic
cavity, with the two regions separated by
the pelvic diaphragm. The following areas are thus classified as parts of the perineal
region: perineal pouches: superficial and deep
(see above for details) Ischioanal fossa – a fat filled space at the lateral sides of anal canal. It is
bounded laterally by obturator internus
muscle, medially by pelvic diaphragm
and anal canal. Its base is the skin. Anal canal Pudendal canal – contains internal pudendal artery and the pudendal nerve.
HYMEN
The hymen is a membrane that surrounds or partially covers the external vaginal opening. It forms part of the vulva , or external genitalia.[1][2] The size of the hymenal opening increases with age.
Although an often practiced method, it is
not possible to confirm with certainty that
a girl or woman is a virgin by examining her hymen.[2] In cases of suspected rape or child sexual abuse, a detailed examination of the hymen may be performed, but the
condition of the hymen alone is often
inconclusive. In younger children, a torn
hymen will typically heal very quickly. In
adolescents, the hymenal opening does
extend from natural causes and variation in shape and appearance increases.[1] In children, although a common appearance
of the hymen is crescent-shaped, many variations are possible.[1] After a woman gives birth, she may be left with remnants of the hymen, called carunculae
myrtiformes, or the hymen may be completely absent.[3] Development The genital tract develops during embryogenesis, from the third week of
gestation to the second trimester, and the
hymen is formed following the vagina. At week seven, the urorectal septum forms
and separates the rectum from the
urogenital sinus. At week nine, the müllerian ducts move
downwards to reach the urogenital sinus,
forming the uterovaginal canal and
inserting into the urogenital sinus. At week 12, the müllerian ducts fuse to
create a primitive uterovaginal canal called
unaleria At month 5, the vaginal canalization is
complete and the fetal hymen is formed
from the proliferation of the sinovaginal
bulbs (where müllerian ducts meet the
urogenital sinus), and becomes perforate
before or shortly after birth. In newborn babies, still under the influence
of the mother's hormones, the hymen is thick, pale pink, and redundant (folds in on
itself and may protrude). For the first two
to four years of life, the infant produces hormones that continue this effect.[4] Their hymenal opening tends to be annular (circumferential).[5] Resorption Past neonatal stage, the diameter of the
hymenal opening (measured within the
hymenal ring) has been proposed to be
approximately 1 mm for each year of age. [6] In children, to make this measurement, a doctor may place a Foley catheter into the vagina and inflate the balloon behind
the hymen to stretch the hymenal margin
and allow for a better examination. In the
normal course of life, the hymenal opening
can also be enlarged by tampon or menstrual cup use, pelvic examinations with a speculum, regular physical activity or sexual intercourse.[1] Once a girl reaches puberty, the hymen tends to become so
elastic that it is not possible to determine
whether a woman uses tampons or not by
examining her hymen. In one survey, only
43% of women reported bleeding the first
time they had intercourse, indicating that the hymens of a majority of women are sufficiently opened. [1][4] The hymen is most apparent in young girls:
At this time, their hymen is thin and less
likely to be redundant, that is to protrude or fold over on itself. [7] In instances of suspected child abuse, doctors use the clock face system to describe the hymenal opening. The 12 o'clock position is below
the urethra, and 6 o'clock is towards the anus, with the patient lying on her back. [8] Infants' hymenal openings tend to be
redundant (sleeve-like, folding in on itself), and may be ring-shaped.[8] By the time a girl reaches school age, this
hormonal influence has ceased, and the
hymen becomes thin, smooth, delicate, and
nearly translucent. It is also very sensitive to touch; a physician who must swab the
area should avoid the hymen and swab the outer vulval vestibule instead.[4] Prepubescent girls' hymenal openings
come in many shapes, depending on
hormonal and activity level, the most
common being crescentic (posterior rim):
no tissue at the 12 o'clock position;
crescent-shaped band of tissue from 1–2 to 10–11 o'clock, at its widest around 6
o'clock. From puberty onwards, depending
on estrogen and activity levels, the hymenal tissue may be thicker, and the
opening is often fimbriated or erratically shaped.[5] After giving birth, the vaginal opening
usually has nothing left but hymenal tags
(carunculae myrtiformes) and is called
"parous introitus". Anatomic anomalies Various types of hymen Anomalies of the female reproductive tract
can result from agenesis or hypoplasia, canalization defects, lateral fusion and
failure of resorption, resulting in various complications.[6] Imperforate:[9][10] hymenal opening nonexistent; will require minor surgery
if it has not corrected itself by puberty
to allow menstrual fluids to escape. Cribriform, or microperforate:
sometimes confused for imperforate,
the hymenal opening appears to be
nonexistent, but has, under close
examination, small openings. Septate: the hymenal opening has one
or more bands extending across the
opening. Hymenorrhaphy Main article: Hymenorrhaphy In some cultures, an intact hymen is highly
valued at marriage mainly to show virginity.[11][12][13] Some women undergo hymenoplasty, a restoration of their hymen for this reason.[13][14] Womb fury In the sixteenth and seventeenth centuries,
medical researchers used the presence of
the hymen, or lack thereof, as founding
evidence of physical diseases such as
"womb-fury" ( hysteria). If not cured, womb-fury would, according to these early doctors, result in death.[15][16] In other animals Due to similar reproductive system
development, many mammals, including
chimpanzees, elephants, manatees, whales, and horses retain hymens.
INTROITUS
Introitus For usage of the term in Christian religion
and music, see introit. The introitus is an entrance that goes into a canal or hollow organ. Introitus is another name for the vaginal orifice. Introitus has also been used for classifying
uterine prolapse: 1st degree prolapse: cervix is in the
vagina 2nd degree: cervix at the level of the
introitus 3rd degree: cervix comes out of the
introitus procidentia: the uterus also comes out of
the introitus
URINARY MEATUS
The urinary meatus (pronounced /miː ˈeɪtəs/ mee-AY-təs) is an orifice of the urethra.
FRENULUM LABIORUM
In female human anatomy, the frenulum labiorum pudendi (aka the fourchette or the posterior commissure of the labia minora) is a frenulum where the labia minora meet posteriorly. Pathology The fourchette may be torn during delivery due to the sudden stretching of the vulval orifice, or during intercourse. To prevent
this tearing in a haphazard manner, obstetricians and, less frequently, midwives may perform an episiotomy, which is a deliberate cut made in the perineum starting from the fourchette and continuing back along the perineum
toward the anus. Sometimes this surgical
cut may extend to involve the perineal
body and thus reduce anal sphicter
function. Thus some obstetricians have
opted to perform a posterio-lateral cut in the perineum to prevent this potential
complication from occurring. The fourchette may also be torn in acts of
violence wherein forced entry occurs such
as rape. When the fourchette gets torn the bleeding which ensues sometimes requires
surgical suturing for containment. Etymology "Fourchette" is French for "little fork",[1][2] and the word is also used as a technical
term for a type of dessert fork. (See frenulum for details on the etymology of that word.)
URETHRA
In anatomy, the urethra (from Greek οὐρήθρα - ourethra) is a tube that connects
the urinary bladder to the genitals for the removal of fluids out of the body. In males,
the urethra travels through the penis, and carries semen as well as urine. In females, the urethra is shorter and emerges above
the vaginal opening. The external urethral sphincter is a striated muscle that allows voluntary control over urination. Anatomy Female urethra In the human female, the urethra is about
1.5–2 inches (4–5 cm) long and exits the
body between the clitoris and the vagina, extending from the internal to the external
urethral orifice. It is placed behind the
symphysis pubis, embedded in the anterior
wall of the vagina, and its direction is
obliquely downward and forward; it is
slightly curved with the concavity directed forward. Its lining is composed of stratified
squamous epithelium, which becomes
transitional near the bladder. The urethra
consists of three coats: muscular, erectile,
and mucous, the muscular layer being a
continuation of that of the bladder. Between the superior and inferior fascia of
the urogenital diaphragm, the female
urethra is surrounded by the Sphincter urethrae (urethral sphincter). Somatic (conscious) innervation of the external urethral sphincter is supplied by the pudendal nerve. The uro-genital sinus may be divided into three component parts. The
first of these is the cranial portion which is
continuous with the allantois and forms
the bladder proper. The pelvic part of the
sinus forms the prostatic urethra and
epithelium as well as the membranous urethra and bulbo urethral glands in the
male and the membranous urethra and
part of the vagina in females. The area
above and on both sides of the female urethra is thought by some[who?] to be sexually sensitive and is sometimes
referred to as the U-spot or urethral erogenous zone. Male urethra In the human male, the urethra is about 8
inches (20 cm) long and opens at the end of
the penis. The urethra provides an exit for urine as well as semen during ejaculation. The urethra is divided into four parts in
men, named after the location: Region Description Epithelium pre-prostatic
urethra This is the
intramural part
of the urethra
and varies
between 0.5
and 1.5 cm in length
depending on
the fullness of
the bladder. Transitional prostatic
urethra Crosses through
the prostate gland. There are several
openings: (1)
the ejaculatory duct receives sperm from the vas deferens and ejaculate
fluid from the seminal vesicle, (2) several prostatic ducts where fluid
from the prostate enters and contributes
to the
ejaculate, (3)
the prostatic utricle, which is merely an
indentation.
These openings
are collectively
called the
verumontanum. Transitional membranous
urethra A small (1 or
2 cm) portion
passing through
the external urethral
sphincter. This is the
narrowest part
of the urethra.
It is located in
the deep perineal pouch. The bulbourethral
glands (Cowper's
gland) are
found posterior
to this region
but open in the spongy urethra. Pseudostratified
columnar spongy
urethra (or penile
urethra) Runs along the
length of the
penis on its
ventral
(underneath)
surface. It is about 15–16 cm
in length, and
travels through
the corpus spongiosum. The ducts from
the urethral gland (gland of Littre) enter
here. The
openings of the bulbourethral
glands are also found here.[1] Some textbooks
will subdivide
the spongy
urethra into
two parts, the
bulbous and pendulous
urethra. Pseudostratified
columnar – proximally, Stratified
squamous – distally The length of a male's urethra, and the fact
it contains a prominent bend, makes catheterization more difficult. The integrity of the urethra can be determined
by a procedure known as retrograde urethrogram. Histology The epithelium of the urethra starts off as transitional cells as it exits the bladder. Further along the urethra there are stratified columnar cells, then stratified squamous cells near the external urethral orifice. There are small mucus-secreting urethral glands, that help protect the epithelium
from the corrosive urine. Length of the urethrae The female urethra is about 4 cm in length. [2] There is inadequate data for the typical length of the male urethra, however a
study of 109 men showed an average
length of 22.3 cm (SD = 2.4 cm), ranging from 15 cm to 29 cm.[3] Medical problems of the urethra Micrograph of urethral cancer (urothelial cell carcinoma), a rare problem of the urethra. Hypospadias and epispadias are forms of abnormal development of the urethra
in the male, where the meatus is not located at the distal end of the penis (it occurs lower than normal with
hypospadias, and higher with
epispadias). In a severe chordee, the urethra can develop between the penis and the scrotum. Infection of the urethra is urethritis, said to be more common in females than
males. Urethritis is a common cause of dysuria (pain when urinating). Related to urethritis is so called urethral syndrome Passage of kidney stones through the urethra can be painful, which can lead to urethral strictures. Cancer of the urethra.
Main article: urethral cancer Foreign bodies in the urethra are
uncommon, but there have been medical
case reports of self-inflicted injuries, a
result of insertion of foreign bodies into the urethra such as an electrical wire.[4] Investigations There is a common misconception among
males that women urinate through the
vagina. Endoscopy of the bladder via the urethra is called cystoscopy. Urine cytology. Sexual physiology The male urethra is the conduit for semen
during sexual intercourse. It also serves as a passage for urine to flow. Urine typically
contains epithelial cells shed from the
urinary tract. Urine cytology evaluates this
urinary sediment for the presence of
cancerous cells from the lining of the
urinary tract, and it is a convenient noninvasive technique for follow-up
analysis of patients treated for urinary
tract cancers. For this process, urine must
be collected in a reliable fashion, and if
urine samples are inadequate, the urinary
tract can be assessed via instrumentation. In urine cytology, collected urine is
examined microscopically. One limitation,
however, is the inability to definitively
identify low-grade cancer cells and urine
cytology is used mostly to identify high-
grade tumors.
SEXUAL PLEASURE
Human sexual activities or human sexual practices or human sexual behavior refers to the manner in which humans experience
and express their sexuality. People engage in a variety of sexual acts from time to
time, and for a wide variety of reasons.
Sexual activity normally results in sexual arousal and physiological changes in the aroused person, some of which are
pronounced while others are more subtle.
Sexual activity also includes conduct and
activities which are intended to arouse the
sexual interest of another, such as
strategies to find or attract partners (mating and display behavior), and personal interactions between individuals,
such as flirting and foreplay. Human sexual activity has biological, physical and emotional aspects. Biologically, it refers to the reproductive mechanism as well as the basic biological
drive that exists in all species and can
encompass sexual intercourse and sexual contact in all its forms. Emotional aspects
deal with the intense personal bonds and emotions generated between sexual partners by a sexual activity. Physical issues around sexuality range from purely medical considerations to concerns about the physiological or even psychological and sociological aspects of sexual behaviour. In some cultures sexual activity is
considered acceptable only within marriage, although premarital and extramarital sex are also common. Some sexual activities are illegal either
universally or in some countries, and some
are considered against the norms of a
society. For example, sexual activity with a
person below some age of consent and sexual assault in general are criminal offenses in many jurisdictions. Types of sexual activity Sexual activity can be classified in a
number of ways. It can refer to acts which
involve one person, such as masturbation, or to two people, such as sexual intercourse, oral sex, or mutual masturbation. If there are more than two participants in the sex act, it may be
referred to as group sex. Autoerotic sexual activity can involve use of dildos, vibrators, anal beads, sybian machines, and other sex toys, though these devices can also be used with a partner. Sexual activity can be classified into the gender and sexual orientation of the participants. Sexual activity can also be classified
according to the relationship of the
participants. For example, the relationships
can be ones of marriage, intimate partners, casual sex partners or anonymous. Sexual activity can be regarded as conventional or as alternative, involving, for example, fetishism and/or BDSM activities.[1][2] Sexual activity can be consensual or under
force or duress. It may be lawful or illegal
or otherwise be contrary to social norms or generally accepted sexual morals. Reasons for sexual activity People engage in sexual activity for any of
a multitude of possible reasons. Although
the evolutionary purpose of sexual activity
is reproduction, most people engage in
sexual activity because of the sexual pleasure they derive from the activity, in which the most heightened pleasure is
derived through orgasm. Erotic pleasure can also be experienced during foreplay and from flirting, and from fetish or BDSM activities.[3][4] Most commonly, people engage in sexual
activity with a person to whom they are sexually attracted; but at times, a person may engage in a sexual activity solely for
the sexual pleasure of the partner, such as
because of an obligation they may have to the partner or because of sympathy or pity they may feel for the partner. Also, a person may engage in sexual
activity for purely monetary
considerations, or to obtain some
advantage from either the partner or the
activity. Furthermore, a man and woman
may engage in sexual intercourse with the objective of conception. Some people engage in hate sex, which occurs between
two people who strongly dislike or annoy
each other. It is related to the idea that
opposition between two people can
heighten sexual tension, attraction and interest.[5][6] It has been shown that sexual activity
plays a large part in the interaction of
social species. Joan Roughgarden, in her book "Evolutions Rainbow: Diversity,
gender and sexuality in nature and people"[7] postulates that this applies equally to humans as it does to other social
species. She explores the purpose of sexual
activity and demonstrates that there are
many functions facilitated by such activity
including pair bonding, group bonding,
dispute resolution and reproduction. Aspects of human sexual behavior Cultural aspects As with other behaviors, human
intelligence and social complexity have
yielded the most complicated sexual
behavior of any animal. Most people
experiment with a range of sexual
activities during their lives, though they tend to engage in only a few of these
regularly. Some people enjoy many
different sexual activities, while others
avoid sexual activities altogether for
religious or other reasons (see chastity, sexual abstinence, asexuality). Some prefer monogamous relationships for sex, and
others may prefer many different partners
throughout their lives. Social aspects Alex Comfort and others propose three potential social aspects of intercourse in
humans, which are not mutually exclusive:
reproductive, relational, and recreational. [8] The development of the contraceptive pill and other highly effective forms of contraception in the mid- and late 20th century has increased people's ability to
segregate these three functions, which still
overlap a great deal and in complex
patterns. For example: A fertile couple may
have intercourse while using contraception
to experience sexual pleasure (recreational) and also as a means of
emotional intimacy (relational), thus
deepening their bonding, making their
relationship more stable and more capable
of sustaining children in the future
(deferred reproductive). This same couple may emphasize different aspects of
intercourse on different occasions, being
playful during one episode of intercourse
(recreational), experiencing deep
emotional connection on another occasion
(relational), and later, after discontinuing contraception, seeking to achieve
pregnancy (reproductive, or more likely
reproductive and relational). Frequency of sexual activity The frequency of sexual intercourse might range from zero (sexual abstinence) to 15 or 20 times a week.[9] In America, the average frequency of sexual intercourse
for married couples is 2 to 3 times a week. [10] It is generally recognized that postmenopausal women experience declines in frequency of sexual intercourse [11] and that average frequency of intercourse declines with age. According to
the Kinsey Institute, average frequency of sexual intercourse in US is 112 times per
year (age 18-29), 86 times per year (age
30-39), and 69 times per year (age 40-49). [12] Safety aspects A rolled-up male condom There are four main risks that arise from
sexual activity. These are unwanted pregnancy, contracting a sexually transmitted disease, physical injury, and psychological injuries. Sexual activity that involves sexual intercourse or even contact of semen with the vagina or vulva carries the chance of
pregnancy. People who want to engage in
such behaviors with a reduced chance of
pregnancy employ any of a variety of
available contraception methods, such as birth control pills, the use of a condom, diaphragms, spermicides, hormonal contraception, and sterilization.[13] Sexual activity that involves contact with
another person's bodily fluids carries the risk of contracting a sexually transmitted disease such as those arising from HIV/ AIDS, chlamydia, syphilis, gonorrhea, and HPV. Safer sex practices try to reduce these risks. These precautions are often seen as
less necessary for sex partners in committed relationships, if they are known
to be free of disease. Some people require
potential sex partners to be tested for
sexually transmitted diseases before engaging in sex.[14] Physical risks vary with the type of sexual
activity being engaged in. The medical
condition and physical limitations of the
participants must be kept in mind. The risk factors are increased by a
condition (temporary or permanent) which
impairs a person's judgment, such as
excess alcohol or other drugs, or emotional states such as loneliness, depression or euphoria. Age and mental capacity of the participants can also affect the risks of
sexual activity. Sexual morality and social norms Main articles: Sexual morality, Religion and sexuality, and Norm (sociology) Most world religions have sought to
address the moral issues that arise from
people's sexuality in society and in human
interactions. Each major religion has
developed moral codes covering issues of sexuality, morality, ethics etc. Though
these moral codes do not address issues of
sexuality directly, they seek to regulate the
situations which can give rise to sexual
interest and to influence people's sexual activities and practices. However, the impact of religious teaching has at times
been limited. For example, though most
religions disapprove of extramarital sexual relations, it has always been widely practiced. Nevertheless, these religious
codes have always had a strong influence
on peoples' attitudes to issues of modesty
in dress, behaviour, speech etc. On the other hand, some people adopt the
view that pleasure is its own justification for sexual activity. Hedonism is a school of thought which argues that pleasure is the only intrinsic good.[15] Human sexual activity, like many other
kinds of activity engaged in by humans, is
generally influenced by social rules that are
culturally specific and vary widely. These
social rules are referred to as sexual morality (what can and can not be done by society's rules) and sexual norms (what is and is not expected). Sexual ethics, morals, and norms relate to
issues including deception/honesty,
legality, fidelity and consent. Some activities, known as sex crimes in some locations, are illegal in some jurisdictions,
including those conducted between (or
among) consenting and competent adults
(examples include sodomy law and adult- adult incest). Some people who are in a relationship but
want to hide homosexual or heterosexual activity from their partner, may solicit
consensual sexual activity with others
through personal contacts, online chat
rooms, or, advertising in select media. Some people engage in various sexual
activities as a business transaction. When
this involves having sex with, or
performing certain actual sexual acts for
another person in exchange for money or
something of value, it is called prostitution. Other aspects of the adult industry include (for example) telephone sex operators, strip clubs, pornography and the like. Legal issues Main article: Sex and the law There are many laws and social customs
which prohibit, or in some way have an
impact on sexual activities. These laws and
customs vary from country to country, and
have varied over time. They cover, for
example, a prohibition to non-consensual sex, to sex outside of marriage, to sexual
activity in public, besides many others.
Many of these restrictions are non-
controversial, but some have been the
subject of public debate. Most societies consider it a serious crime to
force someone to engage in sexual acts or
to engage in sexual activity with someone
who does not consent. This is called sexual assault, and if sexual penetration occurs it is called rape, the most serious kind of sexual assault. The details of this
distinction may vary among different legal
jurisdictions. Also, what constitutes
effective consent in sexual matters varies
from culture to culture and is frequently
debated. Laws regulating the minimum age at which a person can consent to have
sex (age of consent) are frequently the subject of debate, as is adolescent sexual behavior in general. Some societies have forced marriage, where consent may not
be required. Same sex laws Main article: LGBT rights by country or territory Many locales have laws that limit or
prohibit same-sex sexual activity. Minimum age of sexual activity (age of
consent) The laws of each jurisdiction set the
minimum age at which a young person is allowed to engage in sexual activity. [16] The median age of consent seems to range from 16 to 18 years, but laws stating ages
ranging from 9 to 21 do exist. In many
jurisdictions, age of consent is a person's mental or functional age.[17] As a result, victims can be of any chronological age if
their mental age is below the age of consent.[18] Many jurisdictions regard any sexual activity by an adult involving a child
as child sexual abuse. Some jurisdictions forbid sexual activity
outside of legal marriage completely. The
relevant age may also vary by the type of
sexual act, the sex of the actors, or other
restrictions such as abuse of a position of trust. Some jurisdictions may also make allowances for minors engaged in sexual
acts with each other, rather than a hard and fast single age.[citation needed] Incestuous relationships Most jurisdictions prohibit sexual activity
between certain close relatives. These
laws vary to some extent, such acts are
called incestuous. Sexual abuse Main article: Sexual abuse Non-consensual sexual activity or
subjecting an unwilling person to
witnessing a sexual activity are forms of sexual abuse, as well as (in many countries) certain non-consensual
paraphilias such as frotteurism, telephone scatophilia (indecent phonecalls), and non- consensual exhibitionism and voyeurism (known as "indecent exposure" and "peeping tom" respectively). [19] Sexual activity and orientations Heterosexuality Main article: Heterosexuality Heterosexual sexual practices are subject to laws in many places. In some countries,
mostly those where religion has a strong
influence on social policy, marriage laws serve the purpose of encouraging people to
have sex only within marriage. Sodomy laws were seen as discouraging same-sex sexual practices, but may affect opposite-
sex sexual practices. Laws also ban adults
from committing sexual abuse, committing sexual acts with anyone under an age of
consent, performing sexual activities in
public, and engaging in sexual activities for
money (prostitution). Though these laws cover both same-sex and opposite-sex
sexual activities, they may differ in regard
to punishment, and may be more
frequently (or exclusively) enforced on
those who engage in same-sex sexual activities.[20] Different-sex sexual practices may be monogamous, serially monogamous, or polyamorous, and, depending on the definition of sexual practice, abstinent or autoerotic (including masturbation). Different religious and political movements
have tried to influence or control changes
in sexual practices including courting and
marriage, though in most countries changes occur at a slow rate.[21] Homosexuality Main article: Homosexuality People with a homosexual orientation can
express their sexuality in a variety of
ways, and may or may not express it in their behaviors.[22] Research indicates that many lesbians and gay men want, and
succeed in having, committed and durable
relationships. For example, survey data
indicate that between 40% and 60% of
gay men and between 45% and 80% of
lesbians are currently involved in a romantic relationship.[23] It is possible for a person whose sexual
identity is mainly heterosexual to engage
in sexual acts with people of the same sex.
For example, mutual masturbation in the context of what may be considered normal
heterosexual teen development. Gay, lesbian, and bisexual people who pretend to be heterosexual are often referred to as
being closeted, hiding their sexuality in "the closet". "Closet case" is a derogatory
term used to refer to people who hide their
sexuality. Making that orientation (semi-)
public can be called "coming out of the closet" in the case of voluntary disclosure or "outing" in the case of disclosure by others against the subject's wishes. Among
some communities (called "men on the DL"
or "down-low"), same-sex sexual behavior is sometimes viewed as solely for physical
pleasure. Men on the "down-low" may
engage in sex acts with other men while
continuing sexual and romantic
relationships with women. The definition of homosexuality is an arousal or romantic attraction to members
of one's own sex, though people who
engage exclusively in same-sex sexual
practices may not identify themselves as bisexual, gay or lesbian. In sex-segregated environments, individuals may seek
relationships with others of their own
gender (known as situational homosexuality). In other cases, some people may experiment or explore their
sexuality with same (and/or different) sex
sexual activity before defining their sexual identity. Despite stereotypes and common misconceptions, there are no forms of
sexual activity exclusive to same-sex
sexual behavior that can not also be found
in opposite-sex sexual behavior, save those
involving contact of the same sex genitalia
such as tribadism and frot. Pansexuality Main article: Pansexuality Pansexuality (also referred to as omnisexuality)[24] is characterized by the potential for aesthetic attraction, romantic love, or sexual desire towards people without regard for their gender identity or biological sex.[25] Some pansexuals suggest that they are gender-blind; that gender and sex are insignificant or
irrelevant in determining whether they will be sexually attracted to others. [26] As defined in the Oxford English Dictionary, [27] pansexuality "encompasses all kinds of sexuality; not limited or inhibited in sexual
choice with regards to gender or practice." Alternative practices Some people derive sexual pleasure from
engaging in variety of alternative sexual practices, such as fetishism and/or BDSM activities.[2][28] BDSM often involves a consensual power exchange, whereby one person submits to the control of a dominating partner. These
practices can include spanking, bondage, role playing, role reversals, and raising endorphins through the use of whips,
floggers and other implements. Fetishism can take many forms ranging from the desire for certain body parts, for
example large breasts, armpits or foot
worship. The object of desire can often be
shoes, boots, lingerie, clothing, leather or
rubber items. Some non-conventional autoerotic practices can be dangerous. These include erotic asphyxiation and self-bondage. The potential for injury or even death that
exists while engaging in the partnered
versions of these fetishes (choking and bondage, respectively) becomes drastically increased in the autoerotic case due to the isolation and lack of assistance in the
event of a problem.
VULVOVAGINAL HEALTH
Vulvovaginal health is the health and sanitation of the human female vulva and vagina. Conditions Problems affecting this area include: Infection with Candida albicans (candidiasis or "yeast infection") Bacterial vaginosis (BV) associated with the Gardnerella, formerly called "nonspecific vaginitis" Trichomoniasis Vulvodynia Vestibulodynia Urinary bladder infection, urinary tract infection (UTI), cystitis, Urethritis Various types of prolapse (where another pelvic organ protrudes into the
vagina) Lichen Sclerosis (auto-immune disorder) Cervical cancer (may be prevented by Pap smear screening and HPV vaccines ) Genital warts (may be prevented by HPV vaccines ) Vulvar cancer Vulvo-Perineal Localization of
Dermatologic Disorders Systemic disorders may be localized in the vulvo-perineal region. [1] In Langerhans cell histiocytosis, lesions initially are erythematous, purpuric papules and they then become scaly, crusted and sometimes confluent. In Kawasaki disease , an erythematous, desquamating perineal rash may occur in the second week of symptom onset,
almost at the same time as
palmoplantar desquamation. Acrodermatitis enteropathica is a biochemical disorder of zinc
metabolism. Tumoral and Hamartomatous Diseases of
the Vulva Tumoral Diseases Hemangiomas and Vascular Dysplasia
May Involve the Perineal Region Infantile Perianal Pyramidal Protrusion [2] Diaper Dermatitis in Infancy [3] Infectious diseases Vaginitis Perineal dermatitis Viral infections Infestations with pinworms (rare), scabies and lice.[4] Causes The vulva and vagina have a "normal flora" of "friendly" microorganisms (including the lactobacillus which turns milk into yogurt) which help to keep the area healthy. When
the normal balance is disturbed, an
infection can result. Symptoms The generic term for infection of the
vagina is vaginitis. Symptoms may include an unusual or unpleasant discharge,
itching, or pain during intercourse. But vaginal infections may also be present
without any noticeable symptoms. Maintaining health The following measures are advisable for
keeping the vulva and vagina healthy: Washing once a day or so with water but without soap, since soap disturbs the natural pH balance of the vagina. Some, so called pH balanced soaps exist, but their effects remain unclear. Other
measures are seldom necessary or
advisable. Two notable examples: so-
called "feminine hygiene sprays" are
unnecessary, may be generally harmful,
and have been known to cause severe allergic reactions. Vaginal douching is generally not necessary and has been
implicated in helping to cause bacterial vaginosis (BV) and candidiasis ("yeast infections"). After using the toilet, wipe from the front toward the back to avoid
introducing bacteria from the anal area into the vulva . Use non-perfumed, undyed toilet paper. Drink plenty of water and urinate
frequently and as soon as possible when
you feel the need, to help flush bacteria
out of the urinary tract and avoid urinary tract infections. For the same reason, try to urinate before and after sex. Change out of a wet swimsuit or other wet clothes as soon as possible. Avoid fragrances, colors, and
"deodorants" in products that contact
the vulva/vagina: sanitary napkins, tampons, toilet paper. Some women who are sensitive to these substances
should also avoid bubble baths and some
fabric detergents and softeners. Avoid wearing leather trousers, tight jeans, panties made of nylon or other synthetic fabrics, or pantyhose without an all-cotton crotch (not cotton covered by nylon - cut out the nylon panel if
necessary). Anything which has been in contact
with the anal area (see anal sex) should be thoroughly washed with soap and
water or a similar disinfectant before
coming in contact with the vulva or
vagina. Use condoms during heterosexual intercourse, practice safer sex, know your sex partners, ask sex partners to
practice basic hygiene of their genitals.
Use artificial lubrication during the
intercourse if the amount naturally
produced is not enough. Be careful with objects inserted inside
the vagina. Improper insertion of
objects into any body opening can cause
damage: infection, cutting, piercing,
trauma, blood loss, etc. Avoid letting any contaminants inside
the vagina, including dirt but especially
sand. Women who are unable to walk are more likely to have infections. The problem can
be prevented according to above-
mentioned and following measures: Wash crotch and rectal areas (with a
soap-substitute if desired) and large
amount of warm running water, every
morning and evening. The disabled
person can sit on a shower chair with an
open seat or on a toilet. Use a shower head or water container to wash more directly. Use towel to dry. DO NOT use talcum/body powder, if
desired use corn starch powder (corn-
flour) on the skin of the genital area to
absorb perspiration. Avoid sitting on plastic or synthetic
materials for extended lengths of time. Wear loose underpants and change if
soilage or wetness occurs.
VAGINAL OPENING
The vaginal orifice is a median slit below and behind the opening of the urethra; its size varies inversely with that of the hymen.
VULVAL VESTIBULE
The Vulval vestibule (or "Vulvar vestibule") is a part of the vulva between the labia minora into which the urethral opening and the vaginal opening open. Its edge is marked by Hart's Line. The external urethral orifice (orificium
urethræ externum; urinary meatus) is placed about 2.5 cm behind the glans clitoridis and immediately in front of that of the vagina; it usually assumes the form of a short, sagittal cleft with slightly raised
margins. Nearby are the openings of the Skene's ducts. The vaginal orifice is a median slit below
and behind the opening of the urethra; its
size varies inversely with that of the hymen.
VESTIBULAR BULBS
The vestibular bulbs, also known as the clitoral bulbs, are aggregations of erectile tissue that are an internal part of the clitoris. They can also be found throughout the vestibule: next to the clitoral body, clitoral crura, urethra, urethral sponge, and vagina. They are to the left and right of the
urethra, urethral sponge, and vagina. The vestibular bulbs are homologous to the bulb of penis and adjoining part of the corpus spongiosum of the male, and consists of two elongated masses of
erectile tissue, placed one on either side of
the vaginal orifice and united to each other in front by a narrow median band termed
the pars intermedia. Their posterior ends are expanded and are
in contact with the greater vestibular glands; their anterior ends are tapered and joined to one another by the pars
intermedia; their deep surfaces are in
contact with the inferior fascia of the urogenital diaphragm; superficially they are covered by the bulbospongiosus. Physiology During sexual response the bulbs fill with blood, which then becomes trapped,
causing erection. As the clitoral bulbs fill with blood, they tightly cuff the vaginal
opening, causing the vulva to expand
outward. The blood inside the bulb’s erectile tissue is released to the circulatory system by the spasms of orgasm, but if orgasm does not occur, the blood will exit the bulbs over several hours.
LABIA MINORA
The labia minora (singular: labium minus), also known as the inner labia, inner lips, or nymphae,[1] are two flaps of skin on either side of the human vaginal opening, situated between the labia majora (outer labia, or outer lips). Inner lips vary widely
in size, colour, and shape from woman to
woman. The inner lips extend from the clitoris obliquely downward, laterally, and
backward on either side of the vulval vestibule, ending between the bottom of the vulval vestibule and the outer lips. The posterior ends (bottom) of the inner lips are usually joined across the middle line by
a fold of skin, named the frenulum labiorum pudendi or fourchette. On the front, each lip divides into two
portions. The upper part of each lip passes
above the clitoris to meet the upper part of
the other lip—which will probably be a
little larger or smaller—forming a fold
which overhangs the glans clitoridis; this fold is named the preputium clitoridis. The lower part passes beneath the glans
clitoridis and becomes united to its under
surface, forming, with the inner lip of the
opposite side, the frenulum clitoridis. On the opposed surfaces of the labia
minora are numerous sebaceous hair follicles. Size and shape In or around 2004, researchers from the
Department of Gynaeology, Elizabeth
Garret Anderson Hospital in London,
measured the labia and other genital
structures of 50 women from the age of 18
to 50, with a mean age of 35.6. The results were:[2] Measuring Range Mean [SD] Clitoral length (mm) 5–35 19.1
[8.7] Clitoral glans width (mm) 3–10 5.5 [1.7] Clitoris to urethra (mm) 16–45 28.5
[7.1] Labia majora length (cm) 7.0–12.0 9.3 [1.3] Labia minora length (mm) 20–100 60.6
[17.2] Labia minora width
(mm) 7–50 21.8
[9.4] Perineum length (mm) 15–55 31.3
[8.5] Vaginal length (cm) 6.5–12.5 9.6 [1.5] Tanner stage (n) IV 4 ditto V 46 Colour of genital area compared with
surrounding skin (n) Same 9 ditto Darker 41 Rugosity of labia (n) Smooth 14 ditto Moderate 34 ditto Marked 2
MONS PUBIS
In human anatomy or in mammals in general, the mons pubis (Latin for "pubic mound"), also known as the mons veneris (Latin, mound of Venus) or simply the mons, is the adipose tissue lying above the pubic bone of adult females, anterior to the pubic symphysis . The mons pubis forms the anterior portion of the vulva . The size of the mons pubis varies with the
general level of hormone and body fat.
After puberty it is covered with pubic hair and enlarges. In human females this
mound is made of fat and is supposed to be
larger. It provides protection of the pubic
bone during intercourse. In humans, the mons pubis divides into the labia majora (literally "larger lips") on either side of the furrow, known as the pudendal cleft, that surrounds the labia minora, clitoris, vaginal opening, and other structures of the vulval vestibule . The fatty tissue of the mons pubis is sensitive to
estrogen, causing a distinct mound to form
with the onset of puberty. This pushes the
forward portion of the labia majora out
and away from the pubic bone.
LABIA MAJORA
The labia majora (singular: labium majus) are two prominent longitudinal cutaneous folds that extend downward and backward from the mons pubis to the perineum and form the lateral boundaries of the pudendal cleft, which contains the labia minora, interlabial sulci, clitoral hood, clitoral glans, frenulum clitoridis, the Hart's Line, and the vulval vestibule , which contains the external openings of the urethra and the vagina. Each labium majus has two surfaces, an
outer, pigmented and covered with strong,
crisp hairs; and an inner, smooth and beset
with large sebaceous follicles. Between the two there is a considerable
quantity of areolar tissue, fat, and a tissue resembling the dartos tunic of the scrotum, besides vessels, nerves, and glands. The Labia Majora are thicker in front,
where they form by their meeting the anterior commisure of the labia majora. Posteriorly they are not really joined, but
appear to become lost in the neighboring
integument, ending close to — and nearly
parallel with — each other. Together with the connecting skin
between them, they form the posterior commisure of the labia majora or posterior boundary of the pudendum. The interval between the posterior
commissure of the labia majora and the anus, from 2.5 to 3 cm. in length, constitutes the perineum. The labia majora correspond to the scrotum in the male. Between the labia majora and the inner thighs are the labiocrural folds. Between the labia majora and labia
minora are the interlabial sulci.
VULVA
The vulva (from the Latin vulva, plural vulvae. See etymology) is the external genital organs of the female mammal.[1] This article deals with the vulva of the
human being, although the structures are
similar for other mammals. The vulva has many major and minor
anatomical structures, including the labia majora, mons pubis, labia minora, clitoris, bulb of vestibule, vulval vestibule , greater and lesser vestibular glands, and the opening of the vagina. Its development occurs during several phases, chiefly during
the fetal and pubertal periods of time. As the outer portal of the human uterus or womb, it protects its opening by a "double
door": the labia majora (large lips) and the
labia minora (small lips). The vagina is a self-cleaning organ, sustaining healthy microbial flora that flow from the inside out; the vulva needs only simple washing
to assure good vulvovaginal health , without recourse to any internal cleansing. The vulva has a sexual function; these
external organs are richly innervated and
provide pleasure when properly
stimulated. In various branches of art, the
vulva has been depicted as the organ that
has the power both to "give life" (often associated with the womb), and to give sexual pleasure to humankind.[2] The vulva also contains the opening of the
female urethra, and thus serves the vital function of passing urine. Structure Diagram of vulva In human beings, major structures of the vulva are: [3] the mons pubis the labia, consisting of the labia majora and the labia minora the external portion of the clitoris (Latin: Clitoral glans) and the clitoral hood the vulval vestibule the pudendal cleft the frenulum labiorum pudendi or the fourchette the opening (or urinary meatus) of the urethra the opening (or introitus) of the vagina the hymen and Other structures: the perineum the sebaceous glands on labia majora the vaginal glands: Bartholin's glands Paraurethral glands called Skene's glands The soft mound at the front of the vulva is
formed by fatty tissue covering the pubic
bone, and is called the mons pubis. The
term mons pubis is Latin for "pubic mound"
and it is gender-nonspecific. There is,
however, a variant term that specifies gender: in human females, the mons pubis
is often referred to as the mons veneris,
Latin for "mound of Venus" or "mound of love". The mons pubis separates into two
folds of skin called the labia majora,
literally "major (or large) lips". The cleft
between the labia majora is called the pudendal cleft, or cleft of Venus, and it contains and protects the other, more
delicate structures of the vulva. The labia
majora meet again at a flat area between
the pudendal cleft and the anus called the perineum. The color of the outside skin of the labia majora is usually close to the
overall skin color of the individual,
although there is considerable variation.
The inside skin and mucus membrane are often pink or brownish. After the onset of
puberty, the mons pubis and the labia
majora become covered by pubic hair. This hair sometimes extends to the inner thighs
and perineum, but the density, texture,
color, and extent of pubic hair coverage
vary considerably, due to both individual
variation and cultural practices of hair
modification or removal. External images "Betty Dodson's Vulva Illustrations" , showing the wide variety of
appearance of the female vulva. The labia minora are two soft folds of skin
within the labia majora. While labia
minora translates as "minor (or small) lips",
often the "minora" are of considerable
size, and may protrude outside the
"majora". Much of the variation among vulvas lies in the significant differences in
the size, shape, and color of the labia
minora. The clitoris is located at the front of the
vulva, where the labia minora meet. The
visible portion of the clitoris is the clitoral glans. Typically, the clitoral glans is roughly the size and shape of a pea, although it can be significantly larger or smaller. The
clitoral glans is highly sensitive, containing
as many nerve endings as the analogous
organ in males, the glans penis. The point where the labia minora attach to the
clitoris is called the frenulum clitoridis. A prepuce, the clitoral hood, normally covers and protects the clitoris, however in
women with particularly large clitorises or
small prepuces, the clitoris may be partially
or wholly exposed at all times. The clitoral
hood is the female equivalent of the male foreskin.[4] Often the clitoral hood is only partially hidden inside of the pudendal
cleft. The area between the labia minora is
called the vulval vestibule , and it contains the vaginal and urethral openings. The urethral opening (meatus) is located below
the clitoris and just in front of the vagina.
This is where urine passes from the urinary bladder to be disposed of. The opening of the vagina is located at the
bottom of the vulval vestibule, toward the
perineum. The term introitus is more
technically correct than "opening", since
the vagina is usually collapsed, with the
opening closed, unless something is inserted. The introitus is sometimes partly
covered by a membrane called the hymen. The hymen will rupture during the first
episode of vigorous sex, and the blood
produced by this rupture has been seen as
a sign of virginity. However, the hymen may also rupture spontaneously during
exercise (including horseback riding) or be stretched by normal activities such as use
of tampons, or be so minor as to be unnoticeable. In some rare cases, the
hymen may completely cover the vaginal
opening, requiring a surgical incision. Slightly below and to the left and right of
the vaginal opening are two Bartholin glands which produce a waxy, pheromone- containing substance, the purpose of which
is not yet fully known. The appearance of the vulva and the size
of the various parts varies a great deal
from one female to another, and it is also
common for the left and right sides to
differ in appearance. Fluids and odor There are a number of different secretions
associated with the vulva, including urine, sweat, menses, skin oils (sebum), Bartholin's and Skene's gland secretions, and vaginal wall secretions. These
secretions contain a mix of chemicals,
including pyridine, squalene, urea, acetic acid, lactic acid, complex alcohols, glycols, ketones, and aldehydes. During sexual arousal, vaginal lubrication increases. Smegma Smegma is a white substance formed from a combination of dead cells, skin oils,
moisture and naturally occurring bacteria, that forms in mammalian genitalia. In
females it collects around the clitoris and
labial folds. Aliphatic acids Approximately one third of women
produce aliphatic acids. These acids are a pungent class of chemicals which other primate species produce as sexual- olfactory signals. While there is some
debate, researchers often refer to them as
human pheromones. These acids are produced by natural bacteria resident on
the skin. The acid content varies with the menstrual cycle, rising from one day after menstruation, and peaking mid-cycle, just before ovulation. Sexual arousal Main article: Human sexual response cycle Sexual arousal results in a number of physical changes in the vulva. Arousal may
be broken up into four somewhat arbitrary
phases: Excitement, Plateau, Orgasm, and
Resolution. In the left image female genitalia are in the resting state. In the right image the female is sexually aroused, the vulva is moist and the labia are slightly swollen. Excitement Vaginal lubrication begins first. This is caused by vasocongestion of the vaginal walls. Increased blood pooling there causes
moisture to seep from the walls. These
droplets collect together and flow out of
the vagina, moistening the vulva. The labia
majora flatten and spread apart, and the
clitoris and labia minora increase in size. Unlike in men, where sexual excitement
produces large and readily apparent
changes, namely an erection, women are not necessarily aware that vaginal
lubrication and blood engorgement of their
vaginas has occurred. Plateau Increased vasocongestion in the vagina causes it to swell, decreasing the size of
the vaginal opening by about 30%. The
clitoris becomes increasingly erect, and the
glans moves towards the pubic bone,
becoming concealed by the hood. The labia
minora increase considerably in thickness, approximately 2–6 times, causing them to
spread apart, displaying the vaginal
opening. The labia minora sometimes
change considerably in color, going from
pink to red in lighter skinned women who
have not borne a child, or red to dark red in those that have.[citation needed] Orgasm Immediately prior to the female orgasm, the clitoris becomes exceptionally
engorged, causing the glans to appear to retract into the clitoral hood. This is
thought to protect the sensitive glans
during orgasm. However, there is some
doubt that this is the case, since the same
engorgement prior to orgasm occurs in the
male homologous structure, the penis, the function of which is thought to be to
extend the penis as close to the cervix as
possible prior to ejaculation. Rhythmic muscle contractions occur in the outer third of the vagina, as well as the
uterus and anus. They occur initially at a
rate of about one every 0.8 seconds,
becoming less intense and more randomly
spaced as the orgasm continues. An orgasm
may have as few as one or as many as 15 or more contractions, depending on its
intensity. Orgasm may be accompanied by female ejaculation, causing liquid from either the Skene's gland or bladder to be expelled through the urethra. Immediately after orgasm the clitoris may
be so sensitive that any stimulation is
either exciting or uncomfortable. Resolution The pooled blood begins to dissipate,
although at a much slower rate if an
orgasm has not occurred. The vagina and
vaginal opening return to their normal
relaxed state, and the rest of the vulva
returns to its normal size, position and color. Development Fetus Genital tubercle at fourteen weeks. During the first eight weeks of life, both
male and female fetuses have the same
rudimentary reproductive and sexual
organs, and maternal hormones control
their development. Male and female organs
begin to become distinct when the fetus is able to begin producing its own hormones,
although visible determination of the sex is
difficult until after the twelfth week. During the sixth week, the genital tubercle develops in front of the cloacal membrane. The tubercle contains a groove termed the urethral groove. The urogenital sinus (forerunner of the bladder) opens into this
groove. On either side of the groove are
the urogenital folds. Beside the tubercle are a pair of ridges called the labioscrotal swellings. Beginning in the third month of
development, the genital tubercle becomes
the clitoris. The urogenital folds become
the labia minora, and the labioscrotal
swellings become the labia majora. Childhood At birth, the neonate's vulva (and breast tissue—see witch's milk) may be swollen or enlarged as a result of having been
exposed, via the placenta, to her mother's increased levels of hormones. The clitoris is
proportionally larger than it is likely to be
later in life. Within a short period of time
as these hormones wear off, the vulva will
shrink in size. From one year of age until the onset of
puberty, the vulva does not undergo any
change in appearance, other than growing
in proportion with the rest of her body. Puberty The onset of puberty produces a number of changes. The structures of the vulva
become proportionately larger and may
become more pronounced. Coloration may
change and pubic hair develops, first on the labia majora, and later spreading to the
mons pubis, and sometimes the inner
thighs and perineum. In preadolescent girls, the vulva appears to
be positioned further forward than in
adults, showing a larger percentage of the
labia majora and pudendal cleft when
standing. During puberty the mons pubis
enlarges, pushing the forward portion of the labia majora away from the pubic
bone, and parallel to the ground (when
standing). Variations in body fat levels affect the extent to which this occurs. Childbirth During childbirth, the vagina and vulva must stretch to accommodate the baby's
head (approximately 9.5 cm or 3.7 in). This
can result in tears in the vaginal opening,
labia, and clitoris. An episiotomy (a preemptive surgical cutting of the
perineum) is sometimes performed to limit
tearing, but its appropriateness as a
routine procedure is under question. Some of the changes to the vagina and
vulva that occur during pregnancy may become permanent. Post-menopause During menopause, hormone levels decrease, and as this process happens,
reproductive tissues which are sensitive to
these hormones shrink in size. The mons
pubis, labia, and clitoris are reduced in size
in post-menopause, although not usually to
pre-puberty proportions. Sexual homology Main article: Sexual homology Most male and female sex organs originate
from the same tissues during fetal
development; this includes the vulva. The
anatomy of the vulva is related to the
anatomy of the male genitalia by a shared developmental biology. Organs that have a common developmental ancestry in this
way are said to be homologous. The clitoral glans is homologous to the glans penis in males, and the clitoral body and the clitoral crura are homologous to the corpora cavernosa of the penis. The labia majora, labia minora, and clitoral
hood are homologous to the scrotum, shaft skin of the penis, and the foreskin, respectively. The vestibular bulbs beneath the skin of the labia minora are
homologous to the corpus spongiosum, the tissue of the penis surrounding the urethra.
The Bartholin's glands are homologous to the Cowper's glands in males. Society and culture Many peoples have no or few taboos on
exposure of the breasts, but the vulva and
pubic triangle are always the first areas to
be covered. Saartjie Baartman, the so- called "Hottentot Venus" who was
exhibited in London at the beginning of the
nineteenth century, was paid to display
her large buttocks, but she never revealed her vulva. Khoisan women were said to have elongated labia, leading to questions about, and requests to exhibit, their sinus
pudoris, "curtain of shame", or tablier (the
French word for "apron"). To quote Stephen Jay Gould, "The labia minora, or inner lips, of the ordinary female genitalia are
greatly enlarged in Khoi-San women, and may hang down three or four inches below
the vagina when women stand, thus
giving the impression of a separate and enveloping curtain of skin". [5] Baartman never allowed this trait to be exhibited while she was alive. [6] Pubic hair removal is practiced in many cultures and has been common in the western world since the end of the 20th century. Piercings of the vulva include the Christina piercing and the Nefertiti piercing. In some cultures, including modern
Western culture, women have shaved or
otherwise depilated part or all of the vulva. When high-cut swimsuits became
fashionable, women who wished to wear
them would shave the sides of their pubic
triangles, to avoid exhibiting pubic hair. Other women relish the beauty of seeing
their vulva with hair, or completely
hairless, and find one or the other more
comfortable. Depilation of the vulva is a
fairly recent phenomenon in the United States, Canada, and Western Europe, but has been prevalent, usually in the form of
waxing, in many Eastern European and Middle Eastern cultures for centuries, usually due to the idea that it may be more
hygienic, or originating in prostitution and
pornography. Shaving may include all or
nearly all of the hair. Some styles retain a
small amount of hair on either side of the
labia or a strip directly above and in line with the pudendal cleft. Many people object to pubic shaving, which can result in
cuts to the vulva and clitoris, ingrown hairs, pseudofolliculitis barbae (razor bumps) and folliculitis.[7] Since the early days of Islam, Muslim women and men have followed a tradition
to "pluck the armpit hairs and shave the
pubic hairs". This is a preferred practice
rather than an obligation, and could be
carried out by shaving, waxing, cutting,
clipping, or any other method. This is a regular practice that is considered in some
more devout Muslim cultures as a form of
worship, not a shameful practice, while in
other less devout regions it is a practice for
the purpose of good hygiene. (See Islamic hygienical jurisprudence.) The reasons behind removing this hair could also be
applied to the hair on the scrotum and
around the anus, because the purpose is to
be completely clean and pure and keep
away from anything that may cause dirt and impurities.[8] Several forms of piercings can be done in the female genital area. Piercings are
usually performed for aesthetic purposes,
but some forms like the Clitoral hood piercing might also enhance pleasure during sexual intercourse. Though they are
common in traditional cultures, intimate
piercings are a fairly recent trend in western culture.[9][10][11] Altering the female genitalia Main article: Genital modification and mutilation The most prevalent form of genital
alteration in some countries is female genital mutilation (FGM): removal of any part of the female genitalia for cultural,
religious or other non-medical reasons. This
practice is highly controversial as it is often
done to non-consenting minors and for
debatable (often misogynistic) reasons. An
estimated 100 to 140 million girls and women in Africa and Asia have experienced some form of FGM.[12] Labiaplasty: Reduction of the labia minora Female genital surgery includes laser
resurfacing of the labia to remove
wrinkles, labiaplasty (reducing the size of the labia) and vaginal tightening. Some have likened labiaplasty to FGM. [13] In September 2007, the American College of Obstetricians and Gynecologists issued a committee opinion on these and other
female genital surgeries, including “vaginal
rejuvenation,” “designer vaginoplasty,” “revirgination,” and “G-spot amplification.” This opinion states that the safety of these
procedures has not been documented.
ACOG recommends that women seeking
these surgeries need to be informed about
the lack of data supporting these
procedures and the potential associated risks such as infection, altered sensation, dyspareunia, adhesions, and scarring.[14] Etymology The word vulva was taken from the Middle Latin word volva or vulva ("womb, female genitals"), probably from the Old Latin
volvere ("to roll"; lit. "wrapper"). This is
similar to Sanskrit word ulva ("womb"). [15] An alternate term, also from Latin, is genitalia feminina externa[16] (female external genital organs). Alternative terms In slipshod colloquial speech, the term vagina is often wrongly used to refer to
the female genitals generally. The vagina
is a specific internal structure, whereas the
vulva is the whole exterior genitalia. As with nearly any aspect of the human
body involved in sexual or excretory functions, there are many slang words for the vulva. [17] "Cunt," a medieval word for the vulva and once the standard term, has
become in its literal sense a vulgarism, and in other uses one of the strongest abusive obscenities in English-speaking cultures. Depictions of vulva Main article: Depictions of nudity Some cultures have tended to view the
vulva as something shameful that should
be hidden. For example, the term
pudendum, which denotes the external
genitalia, literally means "shameful thing". Some cultures have long celebrated and
even worshipped the vulva. Some Hindu sects revere it under the name yoni, and texts seem to indicate a similar attitude in
some ancient Middle Eastern religions. As an aspect of Goddess worship such reverence may be part of modern Neopagan beliefs, and may be indicated in paleolithic artworks, dubbed by archaeologist Marija Gimbutas "Old Europe". Ancient Greek women kept their vulva hairless so to display their beauty. Origin of the world, Oil painting by Gustave Courbet Rupestrian depictions of vulvae, paleolithic Stylised vulva stone, paleolithic Sheela Na Gig, grotesque figurative sculpture with exaggeration of vulva. Attic red-figure lid. Three female organs and a winged phallus. Slang There are numerous slang words,
euphemisms and synonyoms for the vulva
in English and in other languages. See WikiSaurus:vulva for a list of slang words for vulva. Art L'Origine du monde, the first realistic painting of a vulva in Western art Sheela na Gig, ancient and medieval European carvings Yoni, Sanskrit depictions Clinical relevance See also: Vulvovaginal health Injuries The vulva is extremely sensitive to
pleasure or pain due to its vast number of mechanoreceptors (nerve endings). Mechanoreceptors are pressure sensors in
the human body, responsible for feeling
any external changes. In the vulva, they
number around 8000. Vulvular injuries are
rare because its structure offers some
natural protection, therefore it is protected from various forms of injuries. Disorders This article is in a list format that may be better presented using prose. You can help by converting this article to prose, if appropriate. Editing help is available. (June 2008) Gynaecology is the branch of medicine dealing with the diagnosis and treatment
of the diseases and disorders associated
with the female reproductive organs.
Regular examinations are necessary to
detect any abnormal changes in the vulvar
region. Several pathologies are defined, a complete descriptive listing may be found
in Chapter XIV of the list of ICD-10 codes; the most significant disorders include: Blemishes and cysts Epidermal cysts Angiomas Moles Freckles Lentigos Scars Scarification Vitiligo Tattoos Hypertrophy Sinus pudoris Infections Candidiasis (thrush) Bacterial vaginosis (BV) Warts (due to HPV or condyloma acuminata) Molluscum contagiosum Herpes simplex (genital herpes) Herpes zoster (shingles) Tinea (fungus) Hidradenitis suppurativa Inflammatory diseases Eczema/Dermatitis Lichen simplex (chronic eczema) Psoriasis Lichen sclerosus Lichen planus zoon's vulvitis (zoon's balanitis in men) Pemphigus vulgaris Pemphigoid (mucus membrane pemphigoid, cicratricial pemphigoid,
bullous pemphigoid) Pain syndromes Vulvodynia and vulvular vestibulitis Vaginismus Vulvar cancer Squamous cell carcinoma (the most common kind) Basal cell carcinoma Melanoma Vulvar cancer Symptoms of vulvar cancer include itching,
a lump or sore on the vulva which does not
heal and/or grows larger, and sometimes
discomfort/pain/swelling in the vulval
area. Treatments include vulvectomy – removal of all or part of the vulva. Ulcers Aphthous ulcer Behcet's Disease Developmental disorders Septate vagina Vaginal opening extremely close to the
urethra or anus An imperforate hymen Various stages of genital
masculinization including fused labia, an
absent or partially-formed vagina,
urethra located on the clitoris. Hermaphroditism Other Vulvar Lymphangioma Extramammary Paget's disease Vulvar intraepithelial neoplasia (VIN) Bowen's disease Bowenoid papulosis Vulvar varicose veins Labial adhesions Perineodynia (perineal pain) Desquamative Inflammatory Vaginitis
(DIV) Childbirth tears and Episiotomy related changes
ENDOCRINE GLANDS
Endocrine glands are glands of the endocrine system that secrete their products, hormones, directly into the blood rather than through a duct. The main
endocrine glands include the pituitary gland, pancreas, ovaries, testes, thyroid gland, and adrenal glands. The hypothalamus is a neuroendocrine organ. Other organs which are not so well known for their endocrine activity include the stomach, which produces such hormones as ghrelin. Local chemical messengers, not generally
considered part of the endocrine system,
include autocrines, which act on the cells that secrete them, and paracrines, which act on a different cell type nearby. Target cell specificity The ability of a target cell to respond to a
hormone depends on the presence of
receptors, within the cell or on its plasma
membrane, to which the hormone can
bind. Hormone receptors are dynamic structures.
Changes in number and sensitivity of
hormone receptors may occur in response
to high or low levels of stimulating
hormones. Blood levels of hormones reflect a balance
between secretion and degradation/ excretion. The liver and kidneys are the major organs that degrade hormones;
breakdown products are excreted in urine
and feces. Hormone half-life and duration of activity
are limited and vary from hormone to
hormone. Interaction of hormones at target cells Permissiveness is the situation in which a hormone cannot exert its full effects
without the presence of another hormone. Synergism occurs when two or more hormones produce the same effects in a
target cell and their results are amplified. Antagonism occurs when a hormone opposes or reverses the effect of another
hormone. Control of hormone release Endocrine organs are activated to release
their hormones by humoral, neural, or
hormonal stimuli. Negative feedback is
important in regulating hormone levels in the blood. The nervous system , acting through hypothalamic controls, can in certain cases
override or modulate hormonal effects. Major endocrine organs Pituitary gland (hypophysis) Endocrine glands in the human head and neck and their hormones Main article: Pituitary gland The pituitary gland hangs from the base of the brain by a stalk and is enclosed by bone. It consists of a hormone-producing
glandular portion (anterior pituitary) and a neural portion (posterior pituitary), which is an extension of the hypothalamus. The hypothalamus regulates the hormonal
output of the anterior pituitary and
synthesizes two hormones that it exports
to the posterior pituitary for storage and
later release. Four of the six adenohypophyseal
hormones are tropic hormones that regulate the function of other endocrine
organs. Most anterior pituitary hormones
exhibit a diurnal rhythm of release, which
is subject to modification by stimuli
influencing the hypothalamus. Somatotropic hormone or Growth hormone (GH) is an anabolic hormone that stimulates growth of all body tissues but
especially skeletal muscle and bone. It may
act directly, or indirectly via insulin-like growth factors (IGFs). GH mobilizes fats, stimulates protein synthesis, and inhibits
glucose uptake and metabolism. Secretion
is regulated by growth hormone releasing hormone (GHRH) and growth hormone inhibiting hormone (GHIH), or somatostatin. Hypersecretion causes gigantism in children and acromegaly in adults; hyposecretion in children causes pituitary dwarfism . Thyroid-stimulating hormone (TSH) promotes normal development and activity
of the thyroid gland. Thyrotropin-releasing hormone (TRH) stimulates its release; negative feedback of thyroid hormone
inhibits it. Adrenocorticotropic hormone (ACTH) stimulates the adrenal cortex to release corticosteroids. ACTH release is triggered by corticotropin-releasing hormone (CRH) and inhibited by rising glucocorticoid levels. The gonadotropins—follicle-stimulating hormone (FSH) and luteinizing hormone (LH) regulate the functions of the gonads in
both sexes. FSH stimulates sex cell
production; LH stimulates gonadal hormone production. Gonadotropin levels rise in
response to gonadotropin-releasing hormone (GnRH). Negative feedback of gonadal hormones inhibits gonadotropin
release. Prolactin (PRL) promotes milk production in humans females. Its secretion is prompted
by prolactin-releasing hormone (PRH) and inhibited by prolactin-inhibiting hormone (PIH). The neurohypophysis stores and releases two hypothalamic hormones: Oxytocin stimulates powerful uterine contractions, which trigger labor and
delivery of an infant, and milk ejection
in nursing women. Its release is
mediated reflexively by the
hypothalamus and represents a positive
feedback mechanism. Antidiuretic hormone (ADH) stimulates the kidney tubules to reabsorb and
conserve water, resulting in small
volumes of highly concentrated urine
and decreased plasma osmolality. ADH is
released in response to high solute
concentrations in the blood and inhibited by low solute concentrations
in the blood. Hyposecretion results in
diabetes insipidus. Thyroid gland Main article: Thyroid The thyroid gland is located in the anterior
throat. Thyroid follicles store colloid
containing thyroglobulin, a glycoprotein from which thyroid hormone is derived. Thyroid hormone (TH) includes thyroxine (T4) and triiodothyronine (T3), which increase the rate of cellular metabolism. Consequently, oxygen use and heat
production rise. Secretion of thyroid hormone, prompted by
TSH, requires reuptake of the stored colloid
by the follicle cells and splitting of the
hormones from the colloid for release.
Rising levels of thyroid hormone feed back
to inhibit the pituitary and hypothalamus. Most T4 is converted to T3 (the more active
form) in the target tissues. These hormones
act by turning on gene transcription and
protein synthesis. Graves' disease is the most common cause of hyperthyroidism ; hyposecretion causes cretinism in infants and myxoedema in adults. Calcitonin, produced by the parafollicular cells of the thyroid gland in response to
rising blood calcium levels, depresses blood
calcium levels by inhibiting bone matrix
resorption and enhancing calcium deposit
in bone. Parathyroid glands Main article: Parathyroid gland The parathyroid glands, located on the
dorsal aspect of the thyroid gland, secrete parathyroid hormone (PTH),[1] which causes an increase in blood calcium levels
by targeting bone, the intestine, and the
kidneys. PTH is the antagonist of calcitonin. PTH release is triggered by falling blood
calcium levels and is inhibited by rising
blood calcium levels. Hyperparathyroidism results in hypercalcaemia and all its effects and in extreme bone wasting. Hypoparathyroidism leads to hypocalcaemia, evidenced by tetany and respiratory paralysis. Pancreas Main article: Pancreas The pancreas, located in the abdomen close
to the stomach, is both an exocrine and an endocrine gland. The endocrine portion
(islets of langerhans) releases insulin and
glucagon and smaller amounts of other
hormones to the blood. Glucagon, released by alpha (α) cells when glucose level in blood are low, stimulates
the liver to release glucose to the blood. Insulin is released by beta (β) cells when blood levels of glucose (and amino acids)
are rising. It increases the rate of glucose
uptake and metabolism by most body cells.
Hyposecretion of insulin results in diabetes
mellitus; cardinal signs are polyuria,
polydipsia, and polyphagia. Gonads Main article: Gonad The ovaries of the female, located in the
pelvic cavity, release two main hormones.
Secretion of estrogens by the ovarian follicles begins at puberty under the influence of FSH. Estrogens stimulate
maturation of the female reproductive
system and development of the secondary
sex characteristics. Progesterone is released in response to high blood levels of
LH. It works with estrogens in establishing
the menstrual cycle. The testes of the male begin to produce testosterone at puberty in response to LH. Testosterone promotes maturation of the
male reproductive organs, development of
secondary sex characteristics, and
production of sperm by the testes. Pineal gland Main article: Pineal gland The pineal gland is located in the diencephalon. Its primary hormone is melatonin, which influences daily rhythms and may have an antigonadotropic effect
in humans. Other hormone-producing structures Many body organs not normally considered
endocrine organs contain isolated cell
clusters that secrete hormones. Examples
include the heart (atrial natriuretic peptide); gastrointestinal tract organs (gastrin, secretin, and others); the placenta (hormones of pregnancy—estrogen, progesterone, and others); the kidneys (erythropoietin and renin); the thymus; skin (cholecalciferol); and adipose tissue (leptin and resistin). Developmental aspects of the endocrine
system Endocrine glands derive from all three
germ layers. Those derived from mesoderm
produce steroidal hormones; the others
produce the amino acid–based hormones. The natural decrease in function of the
female’s ovaries during late middle age
results in menopause. The efficiency of all endocrine glands seems to decrease
gradually as aging occurs. This leads to a
generalized increase in the incidence of diabetes mellitus and a lower metabolic rate.
MEDULLA OF OVARY
The medulla of ovary (or Zona vasculosa of Waldeyer) is a highly vascular stroma in the center of the ovary. It forms from embryonic mesenchyme and contains
blood vessels, lymphatic vessels, and
nerves. This stroma forms the tissue of the hilum by which the ovarian ligament is attached, and through which the blood vessels enter:
it does not contain any ovarian follicles.
CORPUS LUTEUM
Section of the ovary. 1. Outer covering. 1’. Attached border. 2. Central stroma. 3. Peripheral stroma. 4. Bloodvessels. 5. Vesicular follicles in their earliest stage. 6, 7, 8. More advanced follicles. 9. An almost
mature follicle. 9’. Follicle from which the ovum has escaped. 10. Corpus luteum. Gray's subject #266 1256 The corpus luteum (Latin for "yellow body") (plural corpora lutea) is a temporary endocrine structure in mammals, involved in production of
relatively high levels of progesterone and moderate levels of estradiol and inhibin A. It is colored as a result of concentrating carotenoids from the diet. Development and structure The corpus luteum develops from an ovarian follicle during the luteal phase of the menstrual cycle or estrous cycle, following the release of a secondary
oocyte from the follicle during ovulation. The follicle first forms a corpus hemorrhagicum before it becomes a corpus luteum, but the term refers to the visible
collection of blood left after rupture of the
follicle that secretes progesterone. While
the oocyte (later the zygote if fertilization occurs) traverses the Fallopian tube into the uterus, the corpus luteum remains in the ovary. The corpus luteum is typically very large
relative to the size of the ovary; in
humans, the size of the structure ranges from under 2 cm to 5 cm in diameter.[1][2] Its cells develop from the follicular cells surrounding the ovarian follicle.[3] Follicular structure Luteal structure Secretion Theca cells Theca
lutein cells androgens[4] and progesterone[4] Granulosa
cells Granulosa
lutein cells progesterone, [3]estrogen[3], and inhibin A[3] [4] Steroidogenesis, with progesterone in yellow field at upper center. The androgens are shown in blue field, and aromatase at lower center - the enzyme present in granulosa lutein cells that convert androgens into estrogens (shown in pink triangle). Like the previous theca cells, the theca
lutein cells lack the aromatase enzyme that is necessary to produce estrogen, so they
can only perform steroidogenesis until formation of androgens.[5] The granulosa lutein cells do have aromatase, and use it
to produce estrogens, using the androgens
previously synthesized by the theca lutein
cells, as the granulosa lutein cells in
themselves do not have the 17α- hydroxylase or 17,20 lyase to produce androgens.[5] Once the corpus luteum regressed the remnant is known as corpus albicans.[6] Function The corpus luteum is essential for
establishing and maintaining pregnancy in
females. The corpus luteum secretes progesterone, which is a steroid hormone responsible for the decidualization of the endometrium (its development) and maintenance, respectively. When egg is not fertilized If the egg is not fertilized, the corpus
luteum stops secreting progesterone and
decays (after approximately 14 days in
humans). It then degenerates into a corpus albicans, which is a mass of fibrous scar tissue. The uterine lining sloughs off without
progesterone and is expelled through the
vagina (in humans and some great apes,
which go through a menstrual cycle). In an estrus cycle, the lining degenerates back to normal size. When egg is fertilized If the egg is fertilized and implantation occurs, the syncytiotrophoblast (derived
from trophoblast) cells of the blastocyst secrete the hormone human chorionic gonadotropin (hCG, or a similar hormone in other species) by day 9 post-fertilization. Human chorionic gonadotropin signals the
corpus luteum to continue progesterone
secretion, thereby maintaining the thick
lining (endometrium) of the uterus and
providing an area rich in blood vessels in which the zygote(s) can develop. From this point on, the corpus luteum is called the
corpus luteum graviditatis. The introduction of prostaglandins at this point causes the degeneration of the
corpus luteum and the abortion of the fetus. However, in placental animals such as humans, the placenta eventually takes over progesterone production and the
corpus luteum degrades into a corpus albicans without embryo/fetus loss. Content of carotenoids The yellow color and name of the corpus
luteum, like that of the macula lutea of the retina, is due to its concentration of certain carotenoids, especially lutein. In 1968, a report indicated that beta-carotene was
synthesized in laboratory conditions in
slices of corpus luteum from cows.
However, attempts have been made to
replicate these findings, but have not
succeeded. The idea is not presently accepted by the scientific community. [7] Rather, the corpus luteum concentrates
carotenoids from the diet of the mammal.
LIQUOR FOLLICULAR
liquor folliculi Follicular fluid is a liquid which fills the follicular antrum and surrounds the ovum in an ovarian follicle. This fluid is rich in hyaluronic acid.
ANTRUM
The follicular antrum is the portion of an ovarian follicle filled with liquor folliculi.
THECA FOLLICULI
The theca folliculi comprise a layer of the ovarian follicles. They appear as the follicles become tertiary follicles. The theca are divided into two layers, the theca interna and the theca externa. The theca interna is responsible for the production of androstenedione, and indirectly the production of 17β estradiol, also called E2, by supplying the neighboring granulosa cells with androstenedione that with the help of the enzyme aromatase can be used as a substrate for this type of estradiol.
PRIMARY OOCYTE
An oocyte, ovocyte, or rarely ocyte, is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in the ovary during female gametogenesis. The female germ cells produce a primordial germ cell (PGC) which
undergoes a mitotic division to form an oogonium. During oogenesis the oogonium
becomes a primary oocyte (pronounced
oh'a-site). Formation Diagram showing the reduction in number of the chromosomes in the process of maturation of the ovum. Main article: Oogenesis The formation of an oocyte is called
oocytogenesis, which is a part of oogenesis.[1] Oogenesis results in the formation of both primary oocytes before birth, and of secondary oocytes after it as part of ovulation. Cell type ploidy/ chromosomes chromatids Process Time of completion Oogonium diploid/46 2N Oocytogenesis (mitosis) third
trimester primary Oocyte diploid/46 2N Ootidogenesis (meiosis 1) (Folliculogenesis) Dictyate in prophase I
until
ovulation secondary Oocyte haploid/23 1N Ootidogenesis (meiosis 2) Halted in
metaphase
II until
fertilization Ootid haploid/23 1N Ootidogenesis (meiosis 3) Minutes
after
fertilization Ovum haploid/23 1N Characteristics Human oocyte with surrounding granulosa cells Cytoplasm Oocytes are rich in cytoplasm which contains yolk granules to nourish the cell
early in development. Nucleus During the primary oocyte stage of
oogenesis, the nucleus is called a germinal vesicle.[2] The only normal human type of secondary
oocyte has the 23rd (sex) chromosome as
23,X (female-determining), whereas sperm
can can have 23,X (female-determining) or
23,Y (male-determining). Nest The space wherein an ovum or immature ovum is located is the cell-nest.[3] Maternal Contributions to the Oocyte Oocyte Poles Because the fate of an oocyte is to become
fertilized and ultimately grow into a fully
functioning organism, it must be ready to
regulate multiple cellular and
developmental processes. The oocyte, a
large and complex cell, must be supplied with numerous molecules that will direct
the growth of the embryo and control
cellular activities. As the oocyte is a
product of female gametogenesis, the maternal contribution to the oocyte and
consequently the newly fertilized egg is
enormous. There are many types of
molecules that are maternally supplied to
the oocyte which will direct various
activities within the growing zygote. Maternal mRNAs and Proteins During the growth of the oocyte, a variety
of maternally transcribed messenger RNAs,
or mRNAs, are supplied by maternal cells. These mRNAs can be stored in mRNP
(message ribonucleoprotein) complexes
and be translated at specific time points,
they can be localized within a specific
region of the cytoplasm, or they can be
homogeneously dispersed within the cytoplasm of the entire oocyte. [4] Maternally loaded proteins can also be localized or ubiquitous throughout the
cytoplasm. The translated products of the
mRNAs and the loaded proteins have
multiple functions; from regulation of
cellular "house-keeping" such as cell cycle
progression and cellular metabolism, to regulation of developmental processes
such as fertilization, activation of zygotic transcription, and formation of body axes. [4] Below are some examples of maternally inherited mRNAs and proteins found in
Xenopus laevis oocytes. Name Type of Maternal
Molecule Localization Function VegT[5] mRNA Vegetal
Hemisphere Transcription
Factor Vg1[6] mRNA Vegetal
Hemisphere Transcription
Factor XXBP-1[7] mRNA Not Known Transcription
Factor CREB[8] Protein Ubiquitous Transcription
Factor FoxH1[9] mRNA Ubiquitous Transcription
Factor p53[10] Protein Ubiquitous Transcription
Factor Lef/Tcf[11] mRNA Ubiquitous Transcription
Factor FGF2[12] Protein Nucleus Not Known FGF2, 4, 9 FGFR1[11] mRNA Not Known FGF
Signaling Ectodermin [13] Protein Animal
Hemisphere Ubiquitin
Ligase PACE4[14] mRNA Vegetal
Hemisphere Proprotein
Convertase Coco[15] Protein Not Known BMP
inhibitor Twisted
Gastrulation [11] Protein Not Known BMP/Chordin
Bindng
Protein fatvg[16] mRNA Vegetal
Hemisphere Germ Cell
Formation
and Cortical
Rotation Maternal Determinants in Xenopus laevis Oocyte Maternal Mitochondria The oocyte receives mitochondria from maternal cells, which will go on to control
embryonic metabolism and apoptotic events.[4] The partitioning of mitochondria is carried out by a system of microtubules which will localize mitochondria
throughout the oocyte. In certain
organisms, such as mammals, paternal
mitochondria brought to the oocyte by the
spermatozoon are degraded through the
attachment of ubiquitinated proteins. The destruction of paternal mitochondria
ensures the strictly maternal inheritance of
mitochondria and mitochondrial DNA or mtDNA.[4] Maternal Nucleolus In mammals, the nucleolus of the oocyte is derived solely from maternal cells. [17] The nucleolus, a structure found within the
nucleus, is the location where rRNA is
transcribed and assembled into ribosomes.
While the nucleolus is dense and inactive in
a mature oocyte, it is required for proper development of the embryo. [17] Maternal Ribosomes Maternal cells also synthesize and
contribute a store of ribosomes that are required for the translation of proteins
before the zygotic genome is activated. In
mammalian oocytes, maternally derived
ribosomes and some mRNAs are stored in a
structure called cytoplasmic lattices. These
cytoplasmic lattices, a network of fibrils, protein, and RNAs, have been observed to
increase in density as the number of
ribosomes decrease within a growing oocyte.[18] Paternal Contributions to the Oocyte The spermatozoon which fertilizes an oocyte will contribute its pronucleus, the other half of the zygotic genome. In some species, the spermatozoon will also
contribute a centriole which will help make up the zygotic centrosome required for the first division. However, in some
species, such as in the mouse, the entire centrosome is acquired maternally.[19] Currently under investigation is the
possibility of other cytoplasmic
contributions made to the embryo by the
spermatozoon. Abnormalities nondisjunction -- a failure of proper homolog separation in meiosis I, or
sister chromatid separation in meiosis II can lead to aneuploidy, in which the oocyte has the wrong number of
chromosomes, for example 22,X or 24,X.
This is the cause of conditions like Down syndrome and Edwards syndrome . It is more likely with advanced maternal age. Some oocytes have multiple nuclei, although it is thought they never
mature.
ZONA PELLUCIDA
The zona pellucida (plural zonae pellucidae) is a glycoprotein membrane surrounding the plasma membrane of an oocyte. It is a vital constitutive part of the latter, external but of essential importance
to it. The zona pellucida first appears in
multilaminar primary oocytes. This structure binds spermatozoa, and is required to initiate the acrosome reaction. In the mouse (the best characterised
mammalian system) the zona glycoprotein, ZP3, is responsible for sperm binding, adhering to proteins on the sperm plasma membrane (GalT). ZP3 is then involved in
the induction of the acrosome reaction,
whereby a spermatozoon releases the
contents of the acrosomal vesicle. The exact characterisation of what occurs in
other species has become more
complicated as further zona proteins have been identified.[1][2] In humans, five days after the fertilization,
the blastocyst performs zona hatching; the zona pellucida degenerates and
decomposes to be replaced by the
underlying layer of trophoblastic cells. The zona pellucida is essential for oocyte death and fertilization. In some older texts, it has also been called zona striata and stratum lucidum[3] (not to be confused with the stratum lucidum of the skin). Immunocontraception Glycoproteins in ZP1, 2, 3 and 4 are targets
for immunocontraception in the human. In non-mammalian animals, the zona
pellucida (called vitelline layer ) plays an important role in preventing cross-
breeding of different species, especially in
species that fertilize outside of the body
(e.g. fish). The zona pellucida is commonly used to
control wildlife population problems by
immunocontraception. When the zona
pellucida of one animal species is injected
into the bloodstream of another, it results
in sterility of the second species due to immune response. This effect can be temporary or permanent, depending on the
method used. In New Jersey, Porcine zona pellucida is used to keep deer populations low, and this process is commonly referred
to as "spay-vac". Zona pellucida glycoproteins There are four major zona pellucida
glycoproteins, termed ZP1-4. ZP1, ZP3 and ZP4 bind to capacitated spermatozoa and induce the acrosome reaction.Successful fertilization depends on the ability of sperm to penetrate extracellular matrix
surrounding eggs. In the mouse: ZP3 allows species-specific sperm binding ZP2 mediates subsequent sperm binding ZP1 cross-links ZP2 and ZP3. Data with native human protein is not
currently available.
CORONA RADIATA
The corona radiata surround an ovum or unfertilized egg cell, and consist of two or
three strata (layers) of follicular cells. They
are attached to the outer protective layer
of the ovum, the zona pellucida, and their main purpose in many animals is to supply vital proteins to the cell.[citation needed] They appear at ovulation, but may disappear eventually after fertilization. The corona radiata are layers of follicle
cells, that protect the secondary oocyte as
it passes through the ruptured follicular
wall, on its way to the infundibulum of the
uterine (AKA fallopian) tubes. In order for
fertilization to occur, the sperm must break through this layer of follicular cells by
secreting the enzyme hyaluronidase. It takes the secretions of dozens of sperm to
weaken the layer enough for one sperm to
penetrate.
GERMINAL EPITHELIUM
Germinal epithelium (female), a layer of cells covering the ovary Germinal epithelium (male), a layer of cells covering the testicle Germ layer, primary tissue layer formed during embryogenesis in animals
OVARIAN FOLLICLE
Ovarian follicles are the basic units of female reproductive biology, each of which
is composed of roughly spherical
aggregations of cells found in the ovary. They contain a single oocyte (immature ovum or egg). These structures are periodically initiated to grow and develop,
culminating in ovulation of usually a single competent oocyte in humans. These eggs/
ova are only developed once every
menstrual cycle (e.g. once a month in
humans). Structure Section of vesicular ovarian follicle of cat. X 50. The cells of the ovarian follicle are the oocyte, granulosa cells and the cells of the internal and external theca layers. Oocyte Each month, one of the ovaries releases a
mature egg, known as an oocyte. A follicle
is an anatomical structure in which the
primary oocyte develops. The nucleus of
such an oocyte is called a germinal vesicle [1] (see picture). Granulosa Granulosa cells within the follicle surround the oocyte; their numbers increase directly
in response to heightened levels of
circulating gonadotropins or decrease in response to testosterone. They also produce peptides involved in ovarian
hormone synthesis regulation. Follicle- stimulating hormone (FSH) induces granulosa cells to express luteinizing hormone (LH) receptors on their surfaces; when circulating LH binds to these receptors, proliferation stops.[2] Thecal The granulosa cells, in turn, are enclosed in
a thin layer of extracellular matrix – the follicular basement membrane or basal
lamina (fibro-vascular coat in picture).
Outside the basal lamina, the layers theca interna and theca externa are found. Development Main article: Folliculogenesis Primordial follicles are indiscernible to the
naked eye. However, these eventually
develop into primary, secondary and
tertiary vesicular follicles. Tertiary
vesicular follicles (also called "mature
vesicular follicles" or "ripe vesicular follicles") are sometimes called Graafian follicles (after Regnier de Graaf). In humans, oocytes are established in the
ovary before birth and may lie dormant awaiting initiation for up to 50 years. [3] After rupturing, the follicle is turned into a corpus luteum. Development of oocytes in ovarian
follicles Main article: Oogenesis In a larger perspective, the whole
folliculogenesis from primordial to
preovulatory follicle is located in the stage
of meiosis I of ootidogenesis in oogenesis. The embryonic development doesn't differ from the male one, but follows the
common path before gametogenesis. Once gametogonia enter the gonadal ridge, however, they attempt to associate with
these somatic cells. Development proceeds
and the gametogonia turns into oogonia,
which become fully surrounded by a layer
of cells (pre-granulosa cells). The Oogonia multiply by dividing
mitotically; this proliferation ends when
the oogonia enter meiosis. The amount of
time that oogonia multiply by mitosis is
not species specific. In the human fetus,
cells undergoing mitosis are seen until the second and third trimester of pregnancy.[4] [5] After beginning the meiotic process, the oogonia (now called primary oocytes) can
no longer replicate. Therefore the total
number of gametes is established at this
time. Once the primary oocytes stop
dividing the cells enter a prolonged ‘resting
phase’. This ‘resting phase’ or dictyate stage can last anywhere up to fifty years
in the human. For several primary oocytes that undergoes
meiosis, only one functional oocyte is
produced. The other two or three cells
produced are called polar bodies. Polar bodies have no function and eventually
deteriorate. The primary oocyte turns into a secondary
oocyte in mature ovarian follicles. Unlike
the sperm, the egg is arrested in the
secondary stage of meiosis until
fertilization. Upon fertilization by sperm, the secondary
oocyte continues the second part of
meiosis and becomes a zygote. Pathology Any ovarian follicle that is larger than
about two centimeters is termed an ovarian cyst . Ovarian function may be measured by gynecologic ultrasonography of follicular volume. Nowadays, ovarian follicle
volumes can be measured rapidly and
automatically from three-dimensionally reconstructed ultrasound images.[6] Rupture of the follicle can result in
abdominal pain (mittelschmerz) and is to be considered in the differential diagnosis in women of childbearing age.[7] Cryopreservation and culture Follicles can develop from ovarian tissue after cryopreservation . Cryopreservation of ovarian tissue is of interest to women who
want to preserve their reproductive
function beyond the natural limit, or whose
reproductive potential is threatened by cancer therapy,[8] for example in hematologic malignancies or breast cancer. [9] For in vitro culture of follicles, there are various techniques to optimize the growth
of follicles, including the use of defined
media, growth factors and three- dimensional extracellular matrix support. [10] Molecular methods and immunoassay can evaluate stage of maturation and guide adequate differentiation.
GRANULOSA CELL
A granulosa cell or follicular cell is a somatic cell of the sex cord that is closely associated with the developing female gamete (called an oocyte or egg) in the ovary of mammals. Anatomy and function In the primary ovarian follicle, and later in follicle development (folliculogenesis), granulosa cells advance to form a
multilayered cumulus oophorus surrounding the oocyte in the preovulatory or Graafian follicle. The major functions of granulosa cells
include the production of sex steroids, as well as myriad growth factors thought to
interact with the oocyte during its development. The sex steroid production
consists of follicle-stimulating hormone (FSH) stimulating granulosa cells to convert androgens (coming from the thecal cells) to estradiol by aromatase during the follicular phase of the menstrual cycle.[1] However, after ovulation the granulosa cells turn into granulosa lutein cells that produce progesterone. The progesterone may maintain a potential pregnancy and causes
production of a thick cervical mucus that
inhibits sperm entry into the uterus. Embryology of ovarian granulosa cells In the development of the urinary and reproductive organs, the oogonia become invaginated in the gonadal ridge. In the 1970’s, evidence emerged that the
first cells to make contact with the oogonia
were of mesonephric origin. It was
suggested that mesonephric cells already
closely associated with the oogonia proliferated throughout development to form the granulosa cell layer.[2][3][4] Recently this hypothesis has been
challenged with some thorough histology.
Sawyer et al. hypothesised that in sheep
most of the granulosa cells develop from
cells of the mesothelium (i.e., epithelial cells from the presumptive surface epithelium of the ovary). [5] The embryological origin of granulosa cells
remains controversial. Cell culture Cell culture of granulosa cells can be performed in vitro. Plating density (number of cells per volume of culture
medium) plays a critical role for the
differentiation. A lower plating density
makes granulosa cells exhibit estrogen
production, while a higher plating density
makes them appear as progesterone producing theca lutein cells.
MEMBRANA GRANULOSA
The larger ovarian follicles consist of an external fibrovascular coat, connected with
the surrounding stroma of the ovary by a network of bloodvessels; and an internal
coat, which consists of several layers of
nucleated cells, called the membrana granulosa. It contains numerous granulosa cells. At one part of the mature follicle the cells
of the membrana granulosa are collected
into a mass which projects into the cavity
of the follicle. This is termed the discus proligerus.
CUMULUS OOPHORUS
At one part of the mature ovarian follicle, the cells of the membrana granulosa are collected into a mass which projects into
the cavity of the follicle. This cluster of cells
is termed the cumulus oophorus (Latin cumulus=heap, Greek oo=egg +
phorus=carrying) discus proligerus, and it is released with the embedded oocyte
during ovulation. In order for fertilization
to occur this layer must be penetrated by
the spermatocyte.
STROMA
Section of the ovary. 1. Outer covering. 1’. Attached border. 2. Central stroma. 3. Peripheral stroma. 4. Bloodvessels. 5. Vesicular follicles in their earliest stage. 6, 7, 8. More advanced follicles. 9. An almost mature follicle. 9’. Follicle from which the ovum has escaped. 10. Corpus luteum. Section of the fold in the mesonephros of a chick embryo of the fourth day. (Stroma of ovary labeled at center left.) Latin stroma ovarii Gray's subject #266 1256 The stroma of the ovary is a peculiar soft tissue, abundantly supplied with blood vessels, consisting for the most part of spindle-shaped cells with a small amount
of ordinary connective tissue. These cells have been regarded by some
anatomists as unstriped muscle cells,
which, indeed, they most resemble; by
others as connective-tissue cells. On the surface of the organ this tissue is
much condensed, and forms a layer (tunica albuginea) composed of short connective- tissue fibers, with fusiform cells between
them. The stroma of the ovary may contain interstitial cells resembling those of the testis.
TUNICA ALBUGINEA
Tunica albuginea. On the surface of the ovary this tissue is much condensed, and forms a layer, the tunica albuginea, composed of short connective-tissue fibers, with fusiform cells between them.
GEMINAL EPITHELIUM
Germinal epithelium Germinal epithelium can refer to: Germinal epithelium (female), a layer of cells covering the ovary Germinal epithelium (male), a layer of cells covering the testicle Germ layer, primary tissue layer formed during embryogenesis in animals
GONADAL RIDGE
In embryology, the gonadal ridge (or genital ridge[1]) is the precursor to the gonads. The gonadal ridge initially consists mainly of mesenchyme and cells of underlying mesonephric origin. Once
oogonia enter this area they attempt to
associate with these somatic cells.
Development proceeds and the oogonia
become fully surrounded by a layer of cells
(pre-granulosa cells). It gives rise to the sex cords. The gonadal ridge appears at
approximately five weeks. A.—Diagram of the primitive urogenital organs in the embryo previous to sexual distinction. * 3. Ureter. * 4. Urinary bladder. * 5. Urachus. * cl. Cloaca. * cp. Elevation which becomes clitoris or penis. * i. Lower part of the intestine. * ls. Fold of integument from which the labia majora or scrotum are formed. * m, m. Right and left Müllerian ducts uniting together and running with the Wolffian ducts in gc, the genital cord. * ot. The gonadal ridge from which either the ovary or testis is formed (upper right). * ug. Sinus urogenitalis. * W. Left Wolffian body. * w, w. Right and left Wolffian ducts.
GAMETE
A gamete (from Ancient Greek γαμέτης gametes "husband" / γαμετή gamete
"wife") is a cell that fuses with another cell during fertilization (conception) in organisms that reproduce sexually. In species that produce two morphologically
distinct types of gametes, and in which
each individual produces only one type, a female is any individual that produces the larger type of gamete—called an ovum (or egg)—and a male produces the smaller tadpole-like type—called a sperm. This is an example of anisogamy or heterogamy, the condition wherein females and males
produce gametes of different sizes (this is
the case in humans; the human ovum is
approximately 20 times larger than the
human sperm cell). In contrast, isogamy is the state of gametes from both sexes being
the same size and shape, and given
arbitrary designators for mating type. The name gamete was introduced by the Austrian biologist Gregor Mendel. Gametes carry half the genetic information of an individual, 1n of each type. Sperm-egg distinction Eggs are relatively few, large, and do not
move, whereas sperm are many, small, and
mobile. The size difference is mostly (but
not entirely) accounted for by the very
large cytoplasm of the egg. Eggs awaiting zygote formation may be anchored either
to something in the environment or by an
organ that contains them; sperm may rely
solely on their own motility or may be
relayed into place by an organ such as pollen to reach the place of zygote formation. Typically many more sperm
than eggs are created and wasted, in the
sense of never fusing with a partner
gamete. The sperm-egg distinction is the basis for
distinguishing between males and
females. Since some algae and fungi have sexual reproduction by combining two
identical gametes, there is no male/female
distinction in these species. This raises the
question as to why most large/familiar
species reproduce by sperm and egg. One
theory for why the male/female distinction is so common is that it
facilitated encounters between gametes, in ancestral marine species.[1] Dissimilarity In contrast to a gamete, the diploid somatic cells of an individual contain one copy of the chromosome set from the
sperm and one copy of the chromosome set
from the egg; that is, the cells of the
offspring have genes expressing
characteristics of both the father and the
mother. A gamete's chromosomes are not exact duplicates of either of the sets of
chromosomes carried in the somatic cells of
the individual that produced the gametes.
They can be hybrids produced through crossover (a form of genetic recombination) of chromosomes, which takes place in meiosis. This hybridization has a random element, and the
chromosomes tend to be a little different in
every gamete that an individual produces.
Additionally, base pairs in chromosomes
often undergo random mutations resulting
in modified DNA (and subsequently, new proteins and phenotypes). This mutation, recombination, and the fact that the two
chromosome sets ultimately come from
either a grandmother or a grandfather on
each parental side account for the genetic dissimilarity of siblings. Plants Plants which reproduce sexually also have
gametes, however, they are produced in
the anther and ovary. They produce pollen and ovules by meiosis, in a similar way to animals. Sex determination In humans, an ovum can carry only an X chromosome (of the X and Y chromosomes), whereas a sperm may carry either an X or a Y; thus the male
sperm determines the sex of any resulting zygote, if the zygote has two X chromosomes it will develop into a female,
if it has an X and a Y chromosome, it will develop into a male.[2] For birds, the female ovum determines the sex of the
offspring, through the ZW sex- determination system.[2] Side note There is some research that indicates it is
the egg that allows the sperm to enter
thereby choosing which sperm fertilizes it.
Thus, even though the sperm is the carrier
of either the X,X or the X,Y, it could be in
fact the case that the egg is the gamete that chooses the sex by defining which
sperm is included.
OVARIAN FOLLICLE
Ovarian follicles are the basic units of female reproductive biology, each of which
is composed of roughly spherical
aggregations of cells found in the ovary. They contain a single oocyte (immature ovum or egg). These structures are periodically initiated to grow and develop,
culminating in ovulation of usually a single competent oocyte in humans. These eggs/
ova are only developed once every
menstrual cycle (e.g. once a month in
humans). Structure Section of vesicular ovarian follicle of cat. X 50. The cells of the ovarian follicle are the oocyte, granulosa cells and the cells of the internal and external theca layers. Oocyte Each month, one of the ovaries releases a
mature egg, known as an oocyte. A follicle
is an anatomical structure in which the
primary oocyte develops. The nucleus of
such an oocyte is called a germinal vesicle [1] (see picture). Granulosa Granulosa cells within the follicle surround the oocyte; their numbers increase directly
in response to heightened levels of
circulating gonadotropins or decrease in response to testosterone. They also produce peptides involved in ovarian
hormone synthesis regulation. Follicle- stimulating hormone (FSH) induces granulosa cells to express luteinizing hormone (LH) receptors on their surfaces; when circulating LH binds to these receptors, proliferation stops.[2] Thecal The granulosa cells, in turn, are enclosed in
a thin layer of extracellular matrix – the follicular basement membrane or basal
lamina (fibro-vascular coat in picture).
Outside the basal lamina, the layers theca interna and theca externa are found. Development Main article: Folliculogenesis Primordial follicles are indiscernible to the
naked eye. However, these eventually
develop into primary, secondary and
tertiary vesicular follicles. Tertiary
vesicular follicles (also called "mature
vesicular follicles" or "ripe vesicular follicles") are sometimes called Graafian follicles (after Regnier de Graaf). In humans, oocytes are established in the
ovary before birth and may lie dormant awaiting initiation for up to 50 years. [3] After rupturing, the follicle is turned into a corpus luteum. Development of oocytes in ovarian
follicles Main article: Oogenesis In a larger perspective, the whole
folliculogenesis from primordial to
preovulatory follicle is located in the stage
of meiosis I of ootidogenesis in oogenesis. The embryonic development doesn't differ from the male one, but follows the
common path before gametogenesis. Once gametogonia enter the gonadal ridge, however, they attempt to associate with
these somatic cells. Development proceeds
and the gametogonia turns into oogonia,
which become fully surrounded by a layer
of cells (pre-granulosa cells). The Oogonia multiply by dividing
mitotically; this proliferation ends when
the oogonia enter meiosis. The amount of
time that oogonia multiply by mitosis is
not species specific. In the human fetus,
cells undergoing mitosis are seen until the second and third trimester of pregnancy.[4] [5] After beginning the meiotic process, the oogonia (now called primary oocytes) can
no longer replicate. Therefore the total
number of gametes is established at this
time. Once the primary oocytes stop
dividing the cells enter a prolonged ‘resting
phase’. This ‘resting phase’ or dictyate stage can last anywhere up to fifty years
in the human. For several primary oocytes that undergoes
meiosis, only one functional oocyte is
produced. The other two or three cells
produced are called polar bodies. Polar bodies have no function and eventually
deteriorate. The primary oocyte turns into a secondary
oocyte in mature ovarian follicles. Unlike
the sperm, the egg is arrested in the
secondary stage of meiosis until
fertilization. Upon fertilization by sperm, the secondary
oocyte continues the second part of
meiosis and becomes a zygote. Pathology Any ovarian follicle that is larger than
about two centimeters is termed an ovarian cyst . Ovarian function may be measured by gynecologic ultrasonography of follicular volume. Nowadays, ovarian follicle
volumes can be measured rapidly and
automatically from three-dimensionally reconstructed ultrasound images.[6] Rupture of the follicle can result in
abdominal pain (mittelschmerz) and is to be considered in the differential diagnosis in women of childbearing age.[7] Cryopreservation and culture Follicles can develop from ovarian tissue after cryopreservation . Cryopreservation of ovarian tissue is of interest to women who
want to preserve their reproductive
function beyond the natural limit, or whose
reproductive potential is threatened by cancer therapy,[8] for example in hematologic malignancies or breast cancer. [9] For in vitro culture of follicles, there are various techniques to optimize the growth
of follicles, including the use of defined
media, growth factors and three- dimensional extracellular matrix support. [10] Molecular methods and immunoassay can evaluate stage of maturation and guide adequate differentiation.
MESOVARIUM
The mesovarium is the portion of the broad ligament of the uterus that covers the ovaries. At first the mesonephros and genital ridge are suspended by a common mesentery, but as the embryo grows the genital ridge gradually becomes pinched off from the
mesonephros, with which it is at first
continuous, though it still remains
connected to the remnant of this body by a
fold of peritoneum. In the male this is the mesorchium, and in the female, this is the mesovarium.
SUSPENSORY LIGAMENT OF OVARY
The suspensory ligament of the ovary, also infundibulopelvic ligament (commonly abbreviated IP ligament or simply IP), is a fold of peritoneum[1] that extends out from the ovary to the wall of the pelvis. Some sources consider it a part of the broad ligament of uterus[2] while other sources just consider it a "termination" of the ligament.[3] The suspensory ligament is directed
upward over the iliac vessels. Contents It contains the ovarian artery, ovarian vein,[1]ovarian plexus,[4] and lymphatic vessels.[3] Composition The suspensory ligament of the ovary is
one continuous tissue that connects the
ovary to the wall of the pelvis. There are
separate names for the two regions of this
tissue. In the anterior region, the suspensory
ligament is attached to the wall of the
pelvis via a continuous tissue called
peritoneum. In the more posterior region, the
suspensory ligament is attached to the
ovary via a continuous tissue called the
broad ligament. In sum, the suspensory ligament consists of
a single connective tissue from that has
different regional notations, the
peritoneum and the broad ligament. Peritoneal relationship pelvic inlet One must understand that most of the
abdominal cavity is lined by a double-
membranous sac called peritoneum . The interior is called the peritoneal cavity, this
is the location of all 'intra-peritoneal'
organs (disambiguation: retro-peritoneal organs ). The most inferior extent of the peritoneum covers the pelvic inlet; in females, this region of the peritoneum is
referred to as the 'broad ligament'. Development Main article: Development of the suspensory ligament of the ovary The suspensory ligament originates from
the mesonephros, which, in turn, originates from intermediate mesoderm.
OVARIAN LIGAMENT
The ovarian ligament (also called the utero-ovarian ligament or proper ovarian ligament) is a fibrous ligament that connects the ovary to the lateral surface of the uterus. This ligament should not be confused with
the suspensory ligament of the ovary , which extends from the ovary in the other
direction. Structure The ovarian ligament is composed of
muscular and fibrous tissue; it extends
from the uterine extremity of the ovary to the lateral aspect of the uterus, just below the point where the uterine tube and uterus meet. The ligament runs in the broad ligament of the uterus, which is a fold of peritoneum rather than a fibrous ligament. Specifically,
it is located in the parametrium.
MENSTRUAL CYCLE
The menstrual cycle is the scientific term for the physiological changes that can occur in fertile women. This article focuses on the human menstrual cycle. The menstrual cycle, under the control of
the endocrine system, is necessary for reproduction. It is commonly divided into three phases: the follicular phase, ovulation, and the luteal phase; although some sources use a different set of phases: menstruation, proliferative phase, and secretory phase.[1] Menstrual cycles are counted from the first day of menstrual
bleeding. Hormonal contraception interferes with the normal hormonal
changes with the aim of preventing
reproduction. Stimulated by gradually increasing
amounts of estrogen in the follicular phase, discharges of blood (menses) slow then
stop, and the lining of the uterus thickens. Follicles in the ovary begin developing under the influence of a complex interplay
of hormones, and after several days one or
occasionally two become dominant (non-
dominant follicles atrophy and die).
Approximately mid-cycle, 24–36 hours
after the Luteinizing Hormone (LH) surges, the dominant follicle releases an ovum, or egg in an event called ovulation. After ovulation, the egg only lives for 24 hours or
less without fertilization while the
remains of the dominant follicle in the
ovary become a corpus luteum; this body has a primary function of producing large
amounts of progesterone. Under the influence of progesterone, the
endometrium (uterine lining) changes to
prepare for potential implantation of an embryo to establish a pregnancy. If implantation does not occur within
approximately two weeks, the corpus
luteum will involute, causing sharp drops in
levels of both progesterone and estrogen.
These hormone drops cause the uterus to
shed its lining and egg in a process termed menstruation. In the menstrual cycle, changes occur in the female reproductive system as well as other systems (which lead to breast tenderness or mood changes, for example). A woman's first menstruation is termed menarche, and occurs typically around age 12-13. The average age of menarche is about 12.5 years in the United States,[2] 12.72 in Canada,[3] 12.9 in the UK[4] and 13.06 ± 0.10 years in Iceland.[5] The end of a woman's reproductive phase is called the menopause, which commonly occurs somewhere between the ages of 45 and
55. Terminology The menarche is one of the later stages of puberty in girls. The average age of menarche in humans is 12–13 years, but is
normal anywhere between ages 8 and 16.
Factors such as heredity, diet and overall health can accelerate or delay menarche.[6] The cessation of menstrual cycles at the
end of a woman's reproductive period is
termed menopause. The average age of menopause in women is 52 years in
industrialised countries such as the UK,
with anywhere between 45 and 55 being
common. Menopause before age 45 is
considered premature in industrialised countries.[7] The age of menopause is largely a result of genetics; however,
illnesses, certain surgeries, or medical
treatments may cause menopause to occur earlier.[8] The length of a woman's menstrual cycle
will typically vary, with some shorter
cycles and some longer cycles. A woman
who experiences variations of less than
eight days between her longest cycles and
shortest cycles is considered to have regular menstrual cycles. It is unusual for a
woman to experience cycle length
variations of less than four days. Length
variation between eight and 20 days is
considered as moderately irregular cycles. Variation of 21 days or more between a
woman's shortest and longest cycle lengths is considered very irregular. [9] Phases The menstrual cycle can be divided into
several different phases. The average
length of each phase is shown below, the
first three are related to changes in the
lining of the uterus whereas the final three
are related to processes occurring in the ovary: Name of phase Average start day assuming
a 28-day
cycle Average end day Menstrual phase
(Menstruation) 1 4 Proliferative phase
(Some sources
include
Menstruation in this
phase) 5 13 Ovulatory phase
(Ovulation) 13 16 Luteal phase (also
known as Secretory
phase) 16 28 Ischemic phase 27 28 Follicular phase 1 13 Menstruation Main article: Menstruation Menstruation is also called menstrual bleeding, menses, catamenia or a period. The flow of menses normally serves as a
sign that a woman has not become pregnant. (However, this cannot be taken as certainty, as a number of factors can
cause bleeding during pregnancy; some factors are specific to early pregnancy, and some can cause heavy flow .)[10][11][12] Levels of estradiol (the main estrogen), progesterone, follicle- stimulating hormone and luteinizing hormone during the menstrual cycle, taking inter-cycle and inter- woman variability into account.[13] Eumenorrhea denotes normal, regular
menstruation that lasts for a few days
(usually 3 to 5 days, but anywhere from 2 to 7 days is considered normal).[14][15] The average blood loss during menstruation is 35 milliliters with 10–80 ml considered normal.[16] (Because of this blood loss, women are more susceptible to iron deficiency than men are.)[17] An enzyme called plasmin inhibits clotting in the menstrual fluid.[18] Painful cramping in the abdomen, back, or
upper thighs is common during the first
few days of menstruation (most women
experience some pain during
menstruation). Severe uterine pain during
menstruation is known as dysmenorrhea, and it is most common among adolescents
and younger women (affecting about 67.2% of adolescent females).[19] When menstruation begins, symptoms of premenstrual syndrome (PMS) such as breast tenderness and irritability generally decrease.[15] Many sanitary products are marketed to women for use during their
menstruation. Follicular phase Main article: Follicular phase This phase is also called the proliferative
phase because a hormone causes the lining
of the uterus to grow, or proliferate, during this time.[20] Through the influence of a rise in follicle stimulating hormone (FSH) during the first days of the cycle, a few ovarian follicles are stimulated.[20] These follicles, which were present at birth[20] and have been developing for the better part of a year in
a process known as folliculogenesis, compete with each other for dominance.
Under the influence of several hormones,
all but one of these follicles will stop
growing, while one dominant follicle in the
ovary will continue to maturity. The follicle
that reaches maturity is called a tertiary, or Graafian, follicle, and it forms the ovum. [20] As they mature, the follicles secrete
increasing amounts of estradiol, an estrogen. The estrogens initiate the formation of a new layer of endometrium in the uterus, histologically identified as
the proliferative endometrium. The
estrogen also stimulates crypts in the cervix to produce fertile cervical mucus, which may be noticed by women practicing fertility awareness .[21] Ovulation Main article: Ovulation An ovary about to release an egg. During the follicular phase, estradiol suppresses production of luteinizing hormone (LH) from the anterior pituitary gland. When the egg has nearly matured, levels of estradiol reach a threshold above which they stimulate production of LH.
These opposite responses of LH to estradiol
may be enabled by the presence of two
different estrogen receptors in the
hypothalamus: estrogen receptor alpha, which is responsible for the negative
feedback estradiol-LH loop, and estrogen receptor beta, which is responsible for the positive estradiol-LH relationship.[22] In the average cycle this LH surge starts
around cycle day 12 and may last 48 hours. The release of LH matures the egg and
weakens the wall of the follicle in the
ovary, causing the fully developed follicle to release its secondary oocyte .[20] The secondary oocyte promptly matures into an ootid and then becomes a mature ovum. The mature ovum has a diameter of about 0.2 mm.[23] Which of the two ovaries—left or right—
ovulates appears essentially random; no
known left and right co-ordination exists. [24] Occasionally, both ovaries will release an egg;[24] if both eggs are fertilized, the result is fraternal twins.[25] After being released from the ovary and
into the peritoneal space, the egg is swept
into the fallopian tube by the fimbria, which is a fringe of tissue at the end of
each fallopian tube. After about a day, an
unfertilized egg will disintegrate or dissolve in the fallopian tube.[20] Fertilization by a spermatozoon, when it occurs, usually takes place in the ampulla, the widest section of the fallopian tubes. A
fertilized egg immediately begins the
process of embryogenesis, or development. The developing embryo takes about three
days to reach the uterus and another three days to implant into the endometrium.[20] It has usually reached the blastocyst stage at the time of implantation. In some women, ovulation features a
characteristic pain called mittelschmerz (German term meaning middle pain).[15] The sudden change in hormones at the
time of ovulation sometimes also causes light mid-cycle blood flow. [26] Luteal phase Main article: Luteal phase The luteal phase is also called the secretory
phase. An important role is played by the corpus luteum, the solid body formed in an ovary after the egg has been released from
the ovary into the fallopian tube. This body
continues to grow for some time after
ovulation and produces significant
amounts of hormones, particularly progesterone.[20] Progesterone plays a vital role in making the endometrium receptive to implantation of the blastocyst and supportive of the early pregnancy; it
also has the side effect of raising the woman's basal body temperature.[27] There is a noted secretion of prolactin
towards the end of the secretory phase.[citation needed] After ovulation, the pituitary hormones FSH and LH cause the remaining parts of
the dominant follicle to transform into the
corpus luteum, which produces
progesterone. The increased progesterone
in the adrenals starts to induce the
production of estrogen. The hormones produced by the corpus luteum also
suppress production of the FSH and LH that
the corpus luteum needs to maintain itself.
Consequently, the level of FSH and LH fall
quickly over time, and the corpus luteum subsequently atrophies.[20] Falling levels of progesterone trigger menstruation and
the beginning of the next cycle. From the
time of ovulation until progesterone
withdrawal has caused menstruation to
begin, the process typically takes about
two weeks, with 14 days considered normal. For an individual woman, the
follicular phase often varies in length from
cycle to cycle; by contrast, the length of her
luteal phase will be fairly consistent from cycle to cycle. [28] The loss of the corpus luteum can be
prevented by fertilization of the egg; the
resulting embryo produces human chorionic gonadotropin (hCG), which is very similar to LH and which can preserve the
corpus luteum. Because the hormone is
unique to the embryo, most pregnancy tests look for the presence of hCG.[20] Length Although many people believe the average
menstrual cycle takes 28 days, a large
study of more than 30,000 cycles from
more than 2300 women showed that the
mean cycle length was 29.1 with a standard deviation of 7.5 days and a 95% prediction interval of between 15 and 45 days.[29] In that study, the subset of data with cycle lengths between 15 and 45 days
had an average length of 28.1 days with a
standard deviation of 4 days. A smaller
study of 140 women performed in 2006 found a mean cycle length of 28.9 days. [30] The variability of menstrual cycle lengths is
highest for women under 25 years of age
and is lowest, that is, most regular, for ages 35 to 39.[29] Subsequently, the variability increases slightly for women aged 40 to 44.[29] Usually, length variation between eight and 20 days in a woman is
considered as moderately irregular menstrual cycles.[9] Variation of 21 days or more is considered very irregular. [9] It has long been thought that cycle length
is associated with the moon. A 1979 study
of 305 women found that approximately
one-third of the subjects had lunar period
cycles, i.e., a mean cycle length of 29.5
days plus or minus 1 day. Almost two- thirds of the subjects started their cycle in
the brighter half of the lunar cycle,
significantly more than would be expected by random distribution.[31] Another study found a statistically significant number of
menstruations occurred around the new moon.[32] Fertile window Main article: fertility testing The most fertile period (the time with the
highest likelihood of pregnancy resulting
from sexual intercourse) covers the time from some 5 days before until 1–2 days after ovulation.[33] In a 28 day cycle with a 14-day luteal phase, this corresponds to
the second and the beginning of the third
week. A variety of methods have been
developed to help individual women
estimate the relatively fertile and the
relatively infertile days in the cycle: these systems are called fertility awareness . Fertility awareness methods that rely on
cycle length records alone are called calendar-based methods.[34] Methods that require observation of one or more of the
three primary fertility signs ( basal body temperature, cervical mucus, and cervical position)[35] are known as symptoms- based methods.[34]Urine test kits are available that detect the LH surge that
occurs 24 to 36 hours before ovulation;
these are known as ovulation predictor kits (OPKs).[36] Computerized devices that interpret basal body temperatures, urinary
test results, or changes in saliva are called fertility monitors. A woman's fertility is also affected by her age.[37] As a woman's total egg supply is formed in fetal life,[38] to be ovulated decades later, it has been suggested that
this long lifetime may make the chromatin of eggs more vulnerable to division
problems, breakage, and mutation than the
chromatin of sperm, which are produced
continuously during a man's reproductive
life. However, despite this hypothesis, a
similar paternal age effect has also been observed. Effect on other systems Some women with neurological conditions experience increased activity of their
conditions at about the same time during
each menstrual cycle. For example, drops in
estrogen levels have been known to
trigger migraines (a neurological syndrome, migraines),[39] especially when the woman who suffers migraines is also
taking the birth control pill. Many women
with epilepsy have more seizures in a pattern linked to the menstrual cycle; this is called "catamenial epilepsy".[40] Different patterns seem to exist (such as
seizures coinciding with the time of
menstruation, or coinciding with the time
of ovulation), and the frequency with
which they occur has not been firmly
established. Using one particular definition, one group of scientists found that around
one-third of women with intractable
partial epilepsy have catamenial epilepsy. [40][41][42] An effect of hormones has been proposed, in which progesterone
declines and estrogen increases would trigger seizures.[43] Recently, studies have shown that high doses of estrogen can
cause or worsen seizures, whereas high
doses of progestrone can act like an antiepileptic drug.[44] Studies by medical journals have found that women
experiencing menses are 1.68 times more likely to commit suicide.[45] Mice have been used as an experimental
system to investigate possible mechanisms
by which levels of sex steroid hormones might regulate nervous system function. During the part of the mouse estrous cycle
when progesterone is highest, the level of nerve-cell GABA receptor subtype delta was high. Since these GABA receptors are inhibitory, nerve cells with more delta receptors are less likely to fire than cells
with lower numbers of delta receptors.
During the part of the mouse estrous cycle
when estrogen levels are higher than
progesterone levels, the number of delta
receptors decrease, increasing nerve cell activity, in turn increasing anxiety and seizure susceptibility.[46] Estrogen levels may affect thyroid behavior.[47] For example, during the luteal phase (when estrogen levels are
lower), the velocity of blood flow in the
thyroid is lower than during the follicular
phase (when estrogen levels are higher). [48] Among women living closely together, it
was once thought that the onsets of
menstruation tend to synchronize. This effect was first described in 1971, and
possibly explained by the action of pheromones in 1998.[49] Subsequent research has called this hypothesis into question.[50] Cycle abnormalities and disorders Main article: Menstrual disorder Infrequent or irregular ovulation is called oligoovulation.[51] The absence of ovulation is called anovulation. Normal menstrual flow can occur without
ovulation preceding it: an anovulatory
cycle. In some cycles, follicular
development may start but not be
completed; nevertheless, estrogens will
form and will stimulate the uterine lining. Anovulatory flow resulting from a very
thick endometrium caused by prolonged,
continued high estrogen levels is called
estrogen breakthrough bleeding.
Anovulatory bleeding triggered by a
sudden drop in estrogen levels is called changes.[52] Anovulatory cycles commonly occur before menopause (perimenopause) and in women with polycystic ovary syndrome.[53] Very little flow (less than 10 ml) is called hypomenorrhea. Regular cycles with intervals of 21 days or fewer are polymenorrhea; frequent but irregular menstruation is known as metrorrhagia. Sudden heavy flows or amounts greater than 80 ml are termed menorrhagia.[54] Heavy menstruation that occurs frequently
and irregularly is menometrorrhagia. The term for cycles with intervals exceeding 35 days is oligomenorrhea.[55]Amenorrhea refers to more than three[54] to six[55] months without menses (while not being
pregnant) during a woman's reproductive
years. Ovulation suppression Hormonal contraception Main article: Hormonal contraception Half-used blister pack of a combined oral contraceptive. The white
pills are placebos, mainly for the purpose of reminding the woman to continue taking the pills. While some forms of birth control do not affect the menstrual cycle, hormonal
contraceptives work by disrupting it.
Progestogen negative feedback decreases the pulse frequency of gonadotropin- releasing hormone (GnRH) release by the hypothalamus, which decreases the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) by the anterior pituitary. Decreased levels of FSH inhibit follicular development, preventing
an increase in estradiol levels. Progestogen negative feedback and the lack of estrogen positive feedback on LH release prevent a mid-cycle LH surge. Inhibition of follicular
development and the absence of a LH surge prevent ovulation. [56][57][58] The degree of ovulation suppression in
progestogen-only contraceptives depends
on the progestogen activity and dose. Low dose progestogen-only contraceptives—
traditional progestogen only pills, subdermal implants Norplant and Jadelle, and intrauterine system Mirena—inhibit ovulation in ~50% of cycles and rely mainly
on other effects, such as thickening of
cervical mucus, for their contraceptive effectiveness. [59] Intermediate dose progestogen-only contraceptives—the
progestogen-only pill Cerazette and the
subdermal implant Implanon—allow some follicular development but more
consistently inhibit ovulation in 97–99% of
cycles. The same cervical mucus changes
occur as with very low dose progestogens.
High dose progestogen-only contraceptives
—the injectables Depo-Provera and Noristerat—completely inhibit follicular development and ovulation. [59] Combined hormonal contraceptives include
both an estrogen and a progestogen.
Estrogen negative feedback on the anterior
pituitary greatly decreases the release of
FSH, which makes combined hormonal
contraceptives more effective at inhibiting follicular development and preventing
ovulation. Estrogen also reduces the
incidence of irregular breakthrough bleeding.[56][57][58] Several combined hormonal contraceptives—the pill, NuvaRing, and the contraceptive patch— are usually used in a way that causes
regular withdrawal bleeding . In a normal cycle, menstruation occurs when estrogen and progesterone levels drop rapidly. [27] Temporarily discontinuing use of combined
hormonal contraceptives (a placebo week,
not using patch or ring for a week) has a
similar effect of causing the uterine lining
to shed. If withdrawal bleeding is not
desired, combined hormonal contraceptives may be taken continuously, although this increases the risk of
breakthrough bleeding. Lactational amenorrhea Main article: Lactational amenorrhea method Breastfeeding causes negative feedback to occur on pulse secretion of gonadotropin-
releasing hormone (GnRH) and luteinizing
hormone (LH). Depending on the strength
of the negative feedback, breastfeeding
women may experience complete
suppression of follicular development, follicular development but no ovulation, or normal menstrual cycles may resume. [60] Suppression of ovulation is more likely when suckling occurs more frequently. [61] The production of prolactin in response to suckling is important to maintaining lactational amenorrhea.[62] On average, women who are fully breastfeeding whose
infants suckle frequently experience a
return of menstruation at fourteen and a
half months postpartum. There is a wide
range of response between individual
breastfeeding women, however, with some experiencing return of menstruation
at two months and others remaining
amenorrheic for up to 42 months postpartum.[63] Etymological and biological associations Nightlighting and the moon See also: Culture and menstruation and Lunar effect The word "menstruation" is etymologically
related to "moon". The terms
"menstruation" and "menses" are derived
from the Latin mensis (month), which in turn relates to the Greek mene (moon) and to the roots of the English words month and moon.[64] Some authors believe women in traditional
societies without nightlighting ovulated
with the full moon and menstruated with the new moon,[65] and one author documents the controversial attempts to
use the association to improve the Rhythm Method of regulating conception.[64][66] A few studies in both humans [67] and other animals[68] have found that artificial light at night does influence the menstrual
cycle in humans and the estrus cycle in
mice (cycles are more regular in the
absence of artificial light at night). It has
also been suggested that bright light
exposure in the morning promotes more regular cycles.[69] One author has suggested that sensitivity of women's
cycles to nightlighting is caused by nutritional deficiencies of certain vitamins and minerals.[70] Some studies show a correlation between
the human menstrual cycle and the lunar
cycle, while a meta-analysis of studies from 1996 showed no correlation.[71][72] [73][74][75][76]Dogon villagers did not have electric lighting and spent most
nights outdoors, talking and sleeping; so
they were an ideal population for
detecting a lunar influence: none, however, was found.
PUBERTY
Puberty is the process of physical changes by which a child's body becomes an adult body capable of reproduction. Puberty is initiated by hormone signals from the brain to the gonads (the ovaries and testes). In response, the gonads produce a variety of hormones that stimulate the
growth, function, or transformation of brain, bones, muscle, blood, skin, hair, breasts, and sex organs. Growth accelerates in the first half of puberty and
stops at the completion of puberty. Before
puberty, body differences between boys
and girls are almost entirely restricted to
the genitalia. During puberty, major
differences of size, shape, composition, and function develop in many body
structures and systems. The most obvious
of these are referred to as secondary sex characteristics. In a strict sense, the term puberty (derived
from the Latin word puberatum (age of
maturity, manhood)) refers to the bodily
changes of sexual maturation rather than the psychosocial and cultural aspects of adolescent development. Adolescence is the period of psychological and social
transition between childhood and adulthood. Adolescence largely overlaps the period of puberty, but its boundaries
are less precisely defined and it refers as
much to the psychosocial and cultural
characteristics of development during the
teen years as to the physical changes of
puberty. Differences between male and female
puberty Two of the most significant differences
between puberty in girls and puberty in
boys are the age at which it begins, and
the major sex steroids involved. Approximate outline of development periods in child and teenager development. Puberty is marked in green at right. Although there is a wide range of normal
ages, girls typically begin the process of
puberty at age 10 or 11; boys at age 12 or 13.[1][2] Girls usually complete puberty by ages 15–17,[2][3][4] while boys usually complete puberty by ages 16–18. [2][3][5] Any increase in height beyond the post-
pubertal age is uncommon. Girls attain
reproductive maturity about 4 years after
the first physical changes of puberty appear.[4] In contrast, boys accelerate more slowly but continue to grow for
about 6 years after the first visible pubertal changes.[6] 1 Follicle-stimulating hormone - FSH 2 Luteinizing hormone - LH 3 Progesterone 4 Estrogen 5 Hypothalamus 6 Pituitary gland 7 Ovary 8 Pregnancy - hCG (Human chorionic gonadotropin) 9 Testosterone 10 Testicle 11 Incentives 12 Prolactin - PRL For boys, an androgen called testosterone is the principal sex hormone. While testosterone produces all boys' changes
characterized as virilization, a substantial product of testosterone metabolism in
males is estradiol, though levels rise later
and more slowly than in girls. The male
"growth spurt" also begins later,
accelerates more slowly, and lasts longer
before the epiphyses fuse. Although boys are on average 2 cm shorter than girls
before puberty begins, adult men are on
average about 13 cm (5.2 inches) taller
than women. Most of this sex difference in
adult heights is attributable to a later onset
of the growth spurt and a slower progression to completion, a direct result of
the later rise and lower adult male levels of estradiol.[7] The hormone that dominates female
development is an estrogen called estradiol. While estradiol promotes growth of breasts and uterus, it is also the principal hormone driving the pubertal growth spurt and epiphyseal maturation and closure.[8] Estradiol levels rise earlier and reach
higher levels in women than in men. Puberty onset The onset of puberty is associated with
high GnRH pulsing, which precedes the rise in sex hormones, LH and FSH.[9] Exogenous GnRH pulses cause the onset of puberty.[10] Brain tumors which increase GnRH output may also lead to premature puberty[11] The cause of the GnRH rise is unknown. Leptin might be the cause of the GnRH rise. Leptin has receptors in the hypothalamus which synthesizes GnRH. [12] Individuals who are deficient in leptin fail to initiate puberty.[13] The levels of leptin increase with the onset of puberty, and then decline
to adult levels when puberty is completed.
The rise in GnRH might also be caused by genetics. A study[14] discovered that a mutation in genes encoding both Neurokinin B as well as the Neurokinin B receptor can alter the timing of puberty.
The researchers hypothesized that
Neurokinin B might play a role in
regulating the secretion of Kisspeptin, a compound responsible for triggering direct
release of GnRH as well as indirect release of LH and FSH. Physical changes in boys This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (October 2009) See also: Tanner scale Testicular size, function, and fertility In boys, testicular enlargement is the first
physical manifestation of puberty (and is termed gonadarche).[15]Testes in prepubertal boys change little in size from
about 1 year of age to the onset of
puberty, averaging about 2–3 cm in length
and about 1.5–2 cm in width. Testicular
size continues to increase throughout
puberty, reaching maximal adult size about 6 years after the onset of puberty. After
the boy's testicles have enlarged and
developed for about one year, the length
and then the breadth of the shaft of the
penis will increase and the glans penis and
corpora cavernosa will also start to enlarge to adult proportions.[16] While 18–20 cm³ is an average adult size, there is wide
variation in testicular size in the normal population.[17] The testes have two primary functions: to
produce hormones and to produce sperm. The Leydig cells produce testosterone, which in turn produces most of the male
pubertal changes. Most of the increasing
bulk of testicular tissue is spermatogenic
tissue (primarily Sertoli and Leydig cells). Sperm can be detected in the morning
urine of most boys after the first year of
pubertal changes, and occasionally earlier[citation needed]. On average, potential fertility in boys is reached at 13
years old, but full fertility will not be
gained until 14–16 years of age[citation needed]. During puberty, a male's scrotum will
become larger and begin to dangle or hang
below the body as opposed to being up
tight, to accommodate the production of
sperm whereby the testicles need a certain
temperature to be fertile. Foreskin retraction During puberty, if not before, the tip and
opening of a boy's foreskin becomes wider, progressively allowing for
retraction down the shaft of the penis and behind the glans, which ultimately should be possible without pain or difficulty. The
membrane that bonds the inner surface of
the foreskin with the glans disintegrates
and releases the foreskin to separate from
the glans. The foreskin then gradually becomes retractable.[18] Research in 1968 by Danish pediatrician
Jakob Øster found that with the onset and
continuation of puberty, the proportion of
boys able to pull back their foreskins
increased. At ages 12–13, Øster found that
only 60% of boys were able to retract their foreskins; this increased to 85% at ages
14–15, and 95% by 16–17 years old. He
also found that only 1% of those unable to
fully retract suffered from phimosis at ages 14–17, the remainder were partially able to.[19] The findings were supported by further research by Japanese doctor
Hiroyuki Kayaba et al in 1996, on a sample of over 600 boys, [20] and in 2004 Ishikawa and Kawakita found that by age 15, 77%
of their sample of boys could retract their foreskins.[21] Once a boy is able to retract his foreskin,
penile hygiene should become an
important feature of his routine body care.
Although the American Academy of Pediatrics states there is "little evidence to affirm the association between
circumcision status and optimal penile hygiene",[22] various studies suggest that uncircumcised boys are educated about the
role of hygiene, including retracting the
foreskin while urinating and rinsing
underneath it and around the glans at each
bathing opportunity. Regular washing
under the foreskin was found, in a 1986 study by Krueger and Osborn, to reduce the risk of numerous penile disorders.[23] Pubic hair Pubic hair often appears on a boy shortly after the genitalia begin to grow. The
pubic hairs are usually first visible at the
dorsal (abdominal) base of the penis. The
first few hairs are described as stage 2.
Stage 3 is usually reached within another
6–12 months, when the hairs are too many to count. By stage 4, the pubic hairs
densely fill the "pubic triangle." Stage 5
refers to the spread of pubic hair to the thighs and upward towards the navel as part of the developing abdominal hair. Body and facial hair Facial hair of a male. In the months and years following the
appearance of pubic hair, other areas of
skin that respond to androgens may
develop androgenic hair. The usual sequence is: underarm (axillary) hair, perianal hair, upper lip hair, sideburn (preauricular) hair, periareolar hair, and the beard area.[2] As with most human biological processes, this specific order
may vary among some individuals. Arm,
leg, chest, abdominal, and back hair become heavier more gradually. There is a
large range in amount of body hair among
adult men, and significant differences in
timing and quantity of hair growth among different racial groups.[1] Facial hair is often present in late adolescence, but may not appear until significantly later.[24][25] Facial hair will continue to get coarser,
darker and thicker for another 2–4 years after puberty.[24] Some men do not develop full facial hair for up to 10 years after the completion of puberty. [24] Chest hair may appear during puberty or years after.[1] Not all men have chest hair. Voice change and Adam's apple Main article: Laryngeal prominence Under the influence of androgens, the voice
box, or larynx, grows in both sexes. This growth is far more prominent in boys,
causing the male voice to drop and deepen,
sometimes abruptly but rarely "over
night," about one octave, because the longer and thicker vocal folds have a lower fundamental frequency. Before puberty, the larynx of boys and girls is about equally small.[26] Occasionally, voice change is accompanied by unsteadiness of
vocalization in the early stages of
untrained voices. Most of the voice change
happens during stage 3-4 of male puberty
around the time of peak growth. Full adult
pitch is attained at an average age of 15 years[citation needed]. It usually precedes the development of significant facial hair
by several months to years. Male musculature and body shape By the end of puberty, adult men have
heavier bones and nearly twice as much skeletal muscle. Some of the bone growth (e.g. shoulder width and jaw) is
disproportionately greater, resulting in
noticeably different male and female
skeletal shapes. The average adult male
has about 150% of the lean body mass of
an average female, and about 50% of the body fat. This muscle develops mainly during the
later stages of puberty, and muscle growth
can continue even after boys are
biologically adult. The peak of the so-called
"strength spurt", the rate of muscle
growth, is attained about one year after a male experiences his peak growth rate. Often, the fat pads of the male breast
tissue and the male nipples will develop
during puberty; sometimes, especially in
one breast, this becomes more apparent
and is termed gynecomastia. It is usually not a permanent phenomenon. Body odor and acne Rising levels of androgens can change the
fatty acid composition of perspiration,
resulting in a more "adult" body odor. As in
girls, another androgen effect is increased
secretion of oil (sebum) from the skin and
the resultant variable amounts of acne. Acne can not be prevented or diminished
easily, but it typically fully diminishes at
the end of puberty. However, it is not
unusual for a fully grown adult to suffer
the occasional bout of acne, though it is
normally less severe than in adolescents. Some may desire using prescription topical
creams or ointments to keep acne from
getting worse, or even oral medication,
due to the fact that acne is emotionally
difficult and can cause scarring. Physical changes in girls Breast development The first physical sign of puberty in girls is
usually a firm, tender lump under the
center of the areola of one or both breasts, occurring on average at about 10.5 years of age.[27] This is referred to as thelarche. By the widely used Tanner staging of puberty, this is stage 2 of breast development
(stage 1 is a flat, prepubertal breast).
Within six to 12 months, the swelling has
clearly begun in both sides, softened, and
can be felt and seen extending beyond the
edges of the areolae. This is stage 3 of breast development. By another 12 months
(stage 4), the breasts are approaching
mature size and shape, with areolae and papillae forming a secondary mound. In most young women, this mound
disappears into the contour of the mature
breast (stage 5), although there is so much
variation in sizes and shapes of adult
breasts that stages 4 and 5 are not always separately identifiable.[28] Pubic hair Pubic hair is often the second noticeable change in puberty, usually within a few months of thelarche.[29] It is referred to as pubarche. The pubic hairs are usually visible first along the labia. The first few hairs are described as Tanner stage 2.[28] Stage 3 is usually reached within another
6–12 months, when the hairs are too
numerous to count and appear on the pubic mound as well. By stage 4, the pubic hairs densely fill the "pubic triangle." Stage 5
refers to spread of pubic hair to the thighs and sometimes as abdominal hair upward towards the navel. In about 15% of girls, the earliest pubic hair appears before breast development begins.[29] Vagina, uterus, ovaries The mucosal surface of the vagina also changes in response to increasing levels of estrogen, becoming thicker and duller pink in color (in contrast to the brighter red of the prepubertal vaginal mucosa).[30] Whitish secretions (physiologic leukorrhea) are a normal effect of estrogen as well. [27] In the two years following thelarche, the uterus, ovaries, and the follicles in the ovaries increase in size.[31] The ovaries usually contain small follicular cysts visible by ultrasound.[32][33] Menstruation and fertility The first menstrual bleeding is referred to as menarche, and typically occurs about two years after thelarche.[29] The average age of menarche is 12.5 in the United States.[34] Most American girls experience their first period at 11, 12 or 13, but some
experience it earlier than their 11th
birthday and others after their 14th
birthday. In fact anytime between 8 and
16 is normal. In Canada the average age of menarche is 12.72,[35] and in the United Kingdom it is 12.9. [36]Ovulation is necessary for fertility, but may or may not accompany the earliest menses.[37] In postmenarchal girls, about 80% of the
cycles were anovulatory in the first year
after menarche, 50% in the third year and 10% in the sixth year.[38] Initiation of ovulation after menarche is not inevitable.
A high proportion of girls with continued
irregularity in the menstrual cycle several
years from menarche will continue to have
prolonged irregularity and anovulation,
and are at higher risk for reduced fertility. [39] Nubility is used to designate achievement of fertility. Body shape, fat distribution, and body
composition During this period, also in response to
rising levels of estrogen, the lower half of
the pelvis and thus hips widen (providing a larger birth canal).[28][40] Fat tissue increases to a greater percentage of the
body composition than in males, especially
in the typical female distribution of
breasts, hips, buttocks, thighs, upper arms,
and pubis. Progressive differences in fat
distribution as well as sex differences in local skeletal growth contribute to the
typical female body shape by the end of
puberty. On average, at 10 years, girls have 6% more body fat than boys. [41] Body odor and acne Rising levels of androgens can change the fatty acid composition of perspiration, resulting in a more "adult" body odor. This often precedes thelarche and pubarche by
one or more years. Another androgen
effect is increased secretion of oil (sebum) from the skin. This change increases the
susceptibility to acne, a skin condition that is characteristic of puberty.[42] Acne varies greatly in its severity. [42] Variations This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (May 2008) Timing of the onset of puberty The definition of the onset of puberty
depends on perspective (e.g., hormonal
versus physical) and purpose (establishing
population normal standards, clinical care
of early or late pubescent individuals, etc.).
The most commonly used definition of the onset of puberty is physical changes to a person's body[citation needed]. These physical changes are the first visible signs
of neural, hormonal, and gonadal function
changes. The age at which puberty begins varies
between individuals; usually, puberty
begins between 10 and 13 years of age.
The age at which puberty begins is
affected by both genetic factors and by
environmental factors such as nutritional state and social circumstances.[1][43] An example of social circumstances is the
Vandenbergh effect; a juvenile female
who has significant interaction with adult
males will enter puberty earlier than
juvenile females who are not socially overexposed to adult males.[44] The average age at which puberty begins
may be affected by race as well. For
example, the average age of menarche in various populations surveyed has ranged
from 12 to 18 years. The earliest average
onset of puberty is for African-American
girls and the latest average onset for high
altitude subsistence populations in Asia.
However, much of the higher age averages reflect nutritional limitations more than
genetic differences and can change within
a few generations with a substantial
change in diet. The median age of
menarche for a population may be an index
of the proportion of undernourished girls in the population, and the width of the
spread may reflect unevenness of wealth
and food distribution in a population. Researchers have identified an earlier age
of the onset of puberty. However, they
have based their conclusions on a
comparison of data from 1999 with data
from 1969. In the earlier example, the
sample population was based on a small sample of white girls (200, from Britain).
The later study identified as puberty as
occurring in 48% of African-American girls
by age nine, and 12% of white girls by that age.[45] Historical shift The average age at which the onset of
puberty occurs has dropped significantly since the 1840s.[46][47][48] This was dubbed 'the secular trend' by J.M. Tanner. In
every decade from 1840 to 1950 there was
a drop of four months in the average age
of menarche among Western European
females. In Norway, girls born in 1840 had their menarche at an average age of 17
years. In France the average in 1840 was
15.3 years. In England the average in 1840 was 16.5 years. In Japan the decline happened later and was then more rapid:
from 1945 to 1975 in Japan there was a
drop of 11 months per decade. A 2006 study in Denmark found that
puberty, as evidenced by breast
development, started at an average age of
9 years and 10 months, a year earlier than
when a similar study was done in 1991.
Scientists believe the phenomenon could be linked to obesity or exposure to
chemicals in the food chain, and is putting
girls at greater long-term risk of breast cancer.[49] Genetic influence and environmental
factors Various studies have found direct genetic
effects to account for at least 46% of the
variation of timing of puberty in well- nourished populations.[50][51][52][53] The genetic association of timing is strongest
between mothers and daughters. The
specific genes affecting timing are not yet known.[50] Among the candidates is an androgen receptor gene.[54] Researchers[55] have hypothesized that early puberty onset may be caused by
certain hair care products containing
estrogen or placenta, and by certain
chemicals, namely phthalates, which are used in many cosmetics, toys, and plastic
food containers. If genetic factors account for half of the
variation of pubertal timing, environment
factors are clearly important as well. One
of the first observed environmental effects
is that puberty occurs later in children
raised at higher altitudes. The most important of the environmental influences
is clearly nutrition, but a number of others
have been identified, all which affect
timing of female puberty and menarche
more clearly than male puberty. Hormones and steroids There is theoretical concern, and animal
evidence, that environmental hormones
and chemicals may affect aspects of prenatal or postnatal sexual development in humans.[56] Large amounts of incompletely metabolized estrogens and progestagens from pharmaceutical products are excreted into the sewage
systems of large cities, and are sometimes
detectable in the environment. Sex steroids are sometimes used in cattle farming but
have been banned in chicken meat
production for 40 years. Although
agricultural laws regulate use to minimize
accidental human consumption, the rules
are largely self-enforced in the United States. Significant exposure of a child to
hormones or other substances that activate
estrogen or androgen receptors could produce some or all of the changes of
puberty. Harder to detect as an influence on puberty
are the more diffusely distributed
environmental chemicals like PCBs
(polychlorinated biphenyl ), which can bind and trigger estrogen receptors. More obvious degrees of partial puberty
from direct exposure of young children to
small but significant amounts of
pharmaceutical sex steroids from exposure
at home may be detected during medical
evaluation for precocious puberty, but mild effects and the other potential exposures
outlined above would not. Bisphenol A (BPA) is a chemical used to make plastics, and is frequently used to
make baby bottles, water bottles, sports
equipment, medical devices, and as a
coating in food and beverage cans.
Scientists are concerned about BPA's
behavioral effects on fetuses, infants, and children at current exposure levels because
it can affect the prostate gland, mammary
gland, and lead to early puberty in girls.
BPA mimics and interferes with the action
of estrogen-an important reproduction and
development regulator. It leaches out of plastic into liquids and foods, and the Centers for Disease Control and Prevention (CDC) found measurable amounts of BPA in
the bodies of more than 90 percent of the
U.S. population studied. The highest
estimated daily intakes of BPA occur in
infants and children. Many plastic baby
bottles contain BPA, and BPA is more likely to leach out of plastic when its
temperature is increased, as when one
warms a baby bottle or warms up food in the microwave. [57] Nutritional influence Nutritional factors are the strongest and most obvious environmental factors affecting timing of puberty. [50] Girls are especially sensitive to nutritional
regulation because they must contribute all
of the nutritional support to a growing
fetus. Surplus calories (beyond growth and activity requirements) are reflected in the
amount of body fat, which signals to the brain the availability of resources for
initiation of puberty and fertility. Much evidence suggests that for most of
the last few centuries, nutritional
differences accounted for majority of
variation of pubertal timing in different
populations, and even among social classes
in the same population. Recent worldwide increased consumption of animal protein,
other changes in nutrition, and increases in
childhood obesity have resulted in falling
ages of puberty, mainly in those
populations with the higher previous ages.
In many populations the amount of variation attributable to nutrition is
shrinking. Although available dietary energy (simple
calories) is the most important dietary
influence on timing of puberty, quality of
the diet plays a role as well. Lower protein intakes and higher dietary fiber intakes, as occur with typical vegetarian diets, are associated with later onset and slower
progression of female puberty. Obesity influence and exercise Scientific researchers have linked early obesity with an earlier onset of puberty in girls. They have cited obesity as a cause of
breast development before nine years and menarche before twelve years. [58] Early puberty in girls can be a harbinger of later health problems.[59] The average level of daily physical activity
has also been shown to affect timing of
puberty, especially in females. A high level
of exercise, whether for athletic or body
image purposes, or for daily subsistence,
reduces energy calories available for reproduction and slows puberty. The
exercise effect is often amplified by a
lower body fat mass and cholesterol. Physical and mental illness Chronic diseases can delay puberty in both
boys and girls. Those that involve chronic
inflammation or interfere with nutrition
have the strongest effect. In the western
world, inflammatory bowel disease and tuberculosis have been notorious for such an effect in the last century, while in areas
of the underdeveloped world, chronic parasite infections are widespread. Mental illnesses occur in puberty. The brain
undergoes significant development by hormones which can contribute to mood disorders such as Major depressive disorder, bipolar disorder, dysthymia and schizophrenia. Girls aged between 15 and 19 make up 40% of anorexia nervosa cases.[60] Stress and social factors Some of the least understood
environmental influences on timing of
puberty are social and psychological. In
comparison with the effects of genetics,
nutrition, and general health, social
influences are small, shifting timing by a few months rather than years. Mechanisms
of these social effects are unknown,
though a variety of physiological
processes, including pheromones, have been suggested based on animal research. The most important part of a child's
psychosocial environment is the family,
and most of the social influence research
has investigated features of family
structure and function in relation to earlier
or later female puberty. Most of the studies have reported that menarche may occur a
few months earlier in girls in high-stress
households, whose fathers are absent
during their early childhood, who have a
stepfather in the home, who are subjected
to prolonged sexual abuse in childhood, or who are adopted from a developing country at a young age. Conversely,
menarche may be slightly later when a girl
grows up in a large family with a
biological father present. More extreme degrees of environmental
stress, such as wartime refugee status
with threat to physical survival, have been
found to be associated with delay of
maturation, an effect that may be
compounded by dietary inadequacy. Most of these reported social effects are
small and our understanding is incomplete.
Most of these "effects" are statistical
associations revealed by epidemiologic surveys. Statistical associations are not
necessarily causal, and a variety of
covariables and alternative explanations
can be imagined. Effects of such small size
can never be confirmed or refuted for any
individual child. Furthermore, interpretations of the data are politically
controversial because of the ease with
which this type of research can be used for
political advocacy. Accusations of bias
based on political agenda sometimes
accompany scientific criticism. Another limitation of the social research is
that nearly all of it has concerned girls,
partly because female puberty requires
greater physiologic resources and partly
because it involves a unique event
(menarche) that makes survey research into female puberty much simpler than
male. More detail is provided in the menarche article. Variations of sequence The sequence of events of pubertal
development can occasionally vary. For
example, in about 15% of boys and girls, pubarche (the first pubic hairs) can precede, respectively, gonadarche and thelarche by a few months. Rarely, menarche can occur before other signs of puberty in a few girls. These variations
deserve medical evaluation because they
can occasionally signal a disease. Conclusion In a general sense, the conclusion of
puberty is reproductive maturity. Criteria
for defining the conclusion may differ for
different purposes: attainment of the
ability to reproduce, achievement of
maximal adult height, maximal gonadal size, or adult sex hormone levels. Maximal
adult height is achieved at an average age
of 15 years for an average girl and 18
years for an average boy. Potential fertility
(sometimes termed nubility) usually
precedes completion of growth by 1–2 years in girls and 3–4 years in boys. Stage
5 typically represents maximal gonadal
growth and adult hormone levels. Neurohormonal process The endocrine reproductive system consists of the hypothalamus, the pituitary, the gonads, and the adrenal glands, with input and regulation from many other body
systems. True puberty is often termed
"central puberty" because it begins as a
process of the central nervous system . A simple description of hormonal puberty is
as follows: 1. The brain's hypothalamus begins to release pulses of GnRH. 2. Cells in the anterior pituitary respond by secreting LH and FSH into the circulation. 3. The ovaries or testes respond to the rising amounts of LH and FSH by
growing and beginning to produce estradiol and testosterone. 4. Rising levels of estradiol and
testosterone produce the body changes
of female and male puberty. The onset of this neurohormonal process
may precede the first visible body changes
by 1–2 years. Components of the endocrine
reproductive system The arcuate nucleus of the hypothalamus is the driver of the reproductive system. It
has neurons which generate and release pulses of GnRH into the portal venous
system of the pituitary gland. The arcuate nucleus is affected and controlled by
neuronal input from other areas of the
brain and hormonal input from the gonads, adipose tissue and a variety of other systems. The pituitary gland responds to the pulsed GnRH signals by releasing LH and FSH into
the blood of the general circulation, also in
a pulsatile pattern. The gonads (testes and ovaries) respond to rising levels of LH and FSH by producing the steroid sex hormones, testosterone and estrogen. The adrenal glands are a second source for steroid hormones. Adrenal maturation,
termed adrenarche, typically precedes gonadarche in mid-childhood. Major hormones Neurokinin B (a tachykinin peptide) and kisspeptin (a neuropeptide), both present in the same hypothalamic neurons, are critical parts of the control system that switches on the release of GnRH at the start of puberty.[61] GnRH (gonadotropin-releasing hormone) is a peptide hormone released from the hypothalamus which stimulates gonadotrope cells of the anterior pituitary. LH (luteinizing hormone) is a larger protein hormone secreted into the general circulation by gonadotrope cells
of the anterior pituitary gland. The main target cells of LH are the Leydig cells of testes and the theca cells of the ovaries. LH secretion changes more dramatically
with the initiation of puberty than FSH,
as LH levels increase about 25-fold with
the onset of puberty, compared with the
2.5-fold increase of FSH. FSH (follicle stimulating hormone) is another protein hormone secreted into
the general circulation by the gonadotrope cells of the anterior pituitary. The main target cells of FSH
are the ovarian follicles and the Sertoli cells and spermatogenic tissue of the testes. Testosterone is a steroid hormone produced primarily by the Leydig cells of the testes, and in lesser amounts by the theca cells of the ovaries and the adrenal cortex. Testosterone is the
primary mammalian androgen and the "original" anabolic steroid. It acts on androgen receptors in responsive tissue throughout the body. Estradiol is a steroid hormone produced by aromatization of testosterone. Estradiol is the principal human estrogen and acts on estrogen receptors throughout the body. The largest
amounts of estradiol are produced by
the granulosa cells of the ovaries, but lesser amounts are derived from testicular and adrenal testosterone. Adrenal androgens are steroids produced by the zona reticulosa of the adrenal cortex in both sexes. The major adrenal androgens are dehydroepiandrosterone, androstenedione (which are precursors of testosterone), and dehydroepiandrosterone sulfate which is present in large amounts in the blood. Adrenal androgens contribute to the
androgenic events of early puberty in
girls. IGF1 (insulin-like growth factor 1 ) rises substantially during puberty in response
to rising levels of growth hormone and may be the principal mediator of the
pubertal growth spurt. Leptin is a protein hormone produced by adipose tissue. Its primary target organ is the hypothalamus. The leptin level seems to provide the brain a rough indicator of adipose mass for purposes
of regulation of appetite and energy metabolism. It also plays a permissive role in female puberty, which usually
will not proceed until an adequate body
mass has been achieved. Endocrine perspective The endocrine reproductive system becomes functional by the end of the first trimester of fetal life. The testes and ovaries become briefly inactive around the
time of birth but resume hormonal activity
until several months after birth, when
incompletely understood mechanisms in
the brain begin to suppress the activity of
the arcuate nucleus. This has been referred to as maturation of the prepubertal
"gonadostat," which becomes sensitive to
negative feedback by sex steroids. The period of hormonal activity until several
months after birth, followed by
suppression of activity, may correspond to
the period of infant sexuality, followed by
a latency stage, which Sigmund Freud described.[62] Gonadotropin and sex steroid levels fall to low levels (nearly undetectable by current clinical assays) for approximately another 8 to 10 years of childhood. Evidence is
accumulating that the reproductive system
is not totally inactive during the childhood
years. Subtle increases in gonadotropin
pulses occur, and ovarian follicles
surrounding germ cells (future eggs) double in number. Normal puberty is initiated in the
hypothalamus, with de-inhibition of the
pulse generator in the arcuate nucleus. This
inhibition of the arcuate nucleus is an
ongoing active suppression by other areas
of the brain. The signal and mechanism releasing the arcuate nucleus from
inhibition have been the subject of
investigation for decades and remain
incompletely understood. Leptin levels rise throughout childhood and play a part in
allowing the arcuate nucleus to resume
operation. If the childhood inhibition of the
arcuate nucleus is interrupted prematurely
by injury to the brain, it may resume
pulsatile gonadotropin release and puberty will begin at an early age. Neurons of the arcuate nucleus secrete gonadotropin releasing hormone (GnRH) into the blood of the pituitary portal
system. An American physiologist, Ernst
Knobil, found that the GnRH signals from
the hypothalamus induce pulsed secretion
of LH (and to a lesser degree, FSH) at
roughly 1-2 hour intervals. The LH pulses are the consequence of pulsatile GnRH
secretion by the arcuate nucleus that, in
turn, is the result of an oscillator or signal generator in the central nervous system ("GnRH pulse generator").[63] In the years preceding physical puberty, Robert M. Boyar discovered that the gonadotropin pulses occur only during sleep, but as
puberty progresses they can be detected during the day.[64] By the end of puberty, there is little day-night difference in the
amplitude and frequency of gonadotropin
pulses. Some investigators have attributed the
onset of puberty to a resonance of oscillators in the brain.[65][66][67][68] By this mechanism, the gonadotropin pulses
that occur primarily at night just before puberty represent beats.[69][70][71] An array of "autoamplification processes"
increases the production of all of the
pubertal hormones of the hypothalamus, pituitary, and gonads[citation needed]. Regulation of adrenarche and its relationship to maturation of the
hypothalamic-gonadal axis is not fully
understood, and some evidence suggests it
is a parallel but largely independent
process coincident with or even preceding
central puberty. Rising levels of adrenal androgens (termed adrenarche) can usually be detected between 6 and 11 years of
age, even before the increasing
gonadotropin pulses of hypothalamic
puberty. Adrenal androgens contribute to
the development of pubic hair (pubarche), adult body odor, and other androgenic changes in both sexes. The primary clinical
significance of the distinction between
adrenarche and gonadarche is that pubic
hair and body odor changes by themselves
do not prove that central puberty is
underway for an individual child. Hormonal changes in boys Early stages of male hypothalamic
maturation seem to be very similar to the
early stages of female puberty, though
occurring about 1–2 years later. LH stimulates the Leydig cells of the testes
to make testosterone and blood levels
begin to rise. For much of puberty,
nighttime levels of testosterone are higher
than daytime. Regularity of frequency and
amplitude of gonadotropin pulses seems to be less necessary for progression of male
than female puberty. However, a significant portion of testosterone in adolescent boys is converted to estradiol. Estradiol mediates
the growth spurt, bone maturation, and
epiphyseal closure in boys just as in girls.
Estradiol also induces at least modest
development of breast tissue
(gynecomastia) in a large proportion of boys. Boys who develop mild gynecomastia or even developing swellings under nipples during puberty are told the effects are temporary in some
male teenagers due to high levels of estradiol. Another hormonal change in males takes
place during the teenage years for most
young men. At this point in a males life the
testosterone levels slowly rise, and most of
the effects are mediated through the
androgen receptors by way of conversion dihydrotestosterone in target organs (especially that of the bowels). Hormonal changes in girls As the amplitude of LH pulses increases,
the theca cells of the ovaries begin to
produce testosterone and smaller amounts
of progesterone. Much of the testosterone moves into nearby cells called granulosa cells. Smaller increases of FSH induce an increase in the aromatase activity of these granulosa cells, which converts most of the
testosterone to estradiol for secretion into
the circulation. Rising levels of estradiol produce the
characteristic estrogenic body changes of
female puberty: growth spurt, acceleration
of bone maturation and closure, breast growth, increased fat composition, growth of the uterus, increased thickness of the endometrium and the vaginal mucosa, and widening of the lower pelvis. As the estradiol levels gradually rise and
the other autoamplification processes
occur, a point of maturation is reached
when the feedback sensitivity of the
hypothalamic "gonadostat" becomes
positive. This attainment of positive feedback is the hallmark of female sexual
maturity, as it allows the mid cycle LH
surge necessary for ovulation. Levels of adrenal androgens and
testosterone also increase during puberty,
producing the typical androgenic changes
of female puberty: pubic hair, other
androgenic hair as outlined above, body
odor, acne. Growth hormone levels rise steadily
throughout puberty. IGF1 levels rise and then decline as puberty ends. Growth
finishes and adult height is attained as the
estradiol levels complete closure of the epiphyses. Stages adrenarche (approximately age 7) gonadarche (approximately age 8) thelarche (approximately age 11 in females) pubarche (approximately age 12) menarche (approximately age 12.5 in females) spermarche (in males)
SECONDARY SEX CHARACTERISTICS
Secondary sex characteristics are features that distinguish the two sexes of a species, but that are not directly part of the reproductive system . They are believed to be the product of sexual selection for traits which give an individual an advantage
over its rivals in courtship and aggressive interactions.[citation needed] They are distinguished from the primary sex
characteristics: the sex organs, which are directly necessary for reproduction to
occur. Well known secondary sex characteristics
include manes of male lions and long feathers of male peacocks. Other dramatic examples include the tusks of male narwhals, enlarged proboscises in male elephant seals and proboscis monkeys, the bright facial and rump coloration of male mandrills, and horns in many goats and antelopes. Male birds and fish of many species have brighter coloration or other
external ornaments. Differences in size between sexes are also considered
secondary sexual characteristics. In humans, visible secondary sex
characteristics include enlarged breasts of females and facial hair on males.
Secondary sex characteristics are features that distinguish the two sexes of a species, but that are not directly part of the reproductive system . They are believed to be the product of sexual selection for traits which give an individual an advantage
over its rivals in courtship and aggressive interactions.[citation needed] They are distinguished from the primary sex
characteristics: the sex organs, which are directly necessary for reproduction to
occur. Well known secondary sex characteristics
include manes of male lions and long feathers of male peacocks. Other dramatic examples include the tusks of male narwhals, enlarged proboscises in male elephant seals and proboscis monkeys, the bright facial and rump coloration of male mandrills, and horns in many goats and antelopes. Male birds and fish of many species have brighter coloration or other
external ornaments. Differences in size between sexes are also considered
secondary sexual characteristics. In humans, visible secondary sex
characteristics include enlarged breasts of females and facial hair on males.
PROGESTERONE
(verify) Progesterone also known as P4 (pregn-4- ene-3,20-dione) is a C-21 steroid hormone involved in the female menstrual cycle, pregnancy (supports gestation) and embryogenesis of humans and other species. Progesterone belongs to a class of
hormones called progestogens, and is the major naturally occurring human
progestogen. Progesterone is commonly manufactured
from the yam family, Dioscorea. Dioscorea produces large amounts of a steroid called diosgenin, which can be converted into progesterone in the laboratory. Chemistry Progesterone was independently discovered by four research groups. [1][2][3] [4] Willard Myron Allen co-discovered progesterone with his anatomy professor
George Washington Corner at the
University of Rochester Medical School in
1933. Allen first determined its melting
point, molecular weight, and partial
molecular structure. He also gave it the name Progesterone derived from Progestational Steroidal ketone.[5] Like other steroids, progesterone consists of four interconnected cyclic hydrocarbons . Progesterone contains ketone and oxygenated functional groups, as well as
two methyl branches. Like all steroid hormones, it is hydrophobic. Sources Animal Progesterone is produced in the ovaries (to be specific, after ovulation in the corpus luteum), the adrenal glands (near the kidney), and, during pregnancy, in the placenta. Progesterone is also stored in adipose (fat) tissue. In humans, increasing amounts of
progesterone are produced during
pregnancy: At first, the source is the corpus luteum
that has been "rescued" by the presence
of human chorionic gonadotropins (hCG) from the conceptus. However, after the 8th week,
production of progesterone shifts to the
placenta. The placenta utilizes maternal
cholesterol as the initial substrate, and
most of the produced progesterone
enters the maternal circulation, but some is picked up by the fetal
circulation and used as substrate for
fetal corticosteroids. At term the placenta produces about 250 mg
progesterone per day. An additional source of progesterone is
milk products. They contain much
progesterone because on dairy farms
cows are milked during pregnancy,
when the progesterone content of the
milk is high. After consumption of milk products the level of bioavailable progesterone goes up.[6] Plants In at least one plant, Juglans regia, progesterone has been detected.[7] In addition, progesterone-like steroids are found in Dioscorea mexicana. Dioscorea mexicana is a plant that is part of the yam family native to Mexico.[8] It contains a steroid called diosgenin that is taken from the plant and is converted into progesterone.[9] Diosgenin and progesterone are found in other Dioscorea species as well. Another plant that contains substances
readily convertible to progesterone is
Dioscorea pseudojaponica native to Taiwan. Research has shown that the Taiwanese yam contains saponins — steroids that can be converted to diosgenin and thence to progesterone.[10] Many other Dioscorea species of the yam
family contain steroidal substances from
which progesterone can be produced.
Among the more notable of these are Dioscorea villosa and Dioscorea polygonoides. One study showed that the
Dioscorea villosa contains 3.5% diosgenin. [11]Dioscorea polygonoides has been found to contain 2.64% diosgenin as shown by gas chromatography-mass spectrometry. [12] Many of the Dioscorea species that originate from the yam family grow in
countries that have tropical and subtropical climates.[13] Synthesis Biosynthesis Top: Conversion of cholesterol (1) into pregnenolone (3) to progesterone (6). Bottom: Progesterone is important for aldosterone (mineralocorticoid) synthesis, as 17-hydroxyprogesterone is for cortisol (glucocorticoid), and androstenedione for sex steroids. In mammals, progesterone (6), like all other steroid hormones, is synthesized from pregnenolone (3), which in turn is derived from cholesterol (1) (see the upper half of the figure to the right). Cholesterol (1) undergoes double oxidation to produce 20,22-dihydroxycholesterol ( 2). This vicinal diol is then further oxidized with loss of the side chain starting at
position C-22 to produce pregnenolone (3). This reaction is catalyzed by cytochrome P450scc. The conversion of pregnenolone to progesterone takes place in two steps.
First, the 3-hydroxyl group is oxidized to a keto group (4) and second, the double bond is moved to C-4, from C-5 through a keto/ enol tautomerization reaction.[14] This reaction is catalyzed by 3beta- hydroxysteroid dehydrogenase/delta(5)-
delta(4)isomerase. Progesterone in turn (see lower half of
figure to the right) is the precursor of the
mineralocorticoid aldosterone, and after conversion to 17-hydroxyprogesterone (another natural progestogen) of cortisol and androstenedione. Androstenedione can be converted to testosterone, estrone and estradiol. Pregenolone and progesterone can also be synthesized by yeast. [15] Laboratory The Marker semisynthesis of progesterone from diosgenin.[16] An economical semisynthesis of progesterone from the plant steroid diosgenin isolated from yams was developed by Russell Marker in 1940 for the Parke-Davis pharmaceutical company (see figure to the right).[16] This synthesis is known as the Marker degradation. Additional semisyntheses of progesterone
have also been reported starting from a
variety of steroids. For the example, cortisone can be simultaneously deoxygenated at the C-17 and C-21
position by treatment with
iodotrimethylsilane in chloroform to produce 11-keto-progesterone
(ketogestin), which in turn can be reduced at position-11 to yield progesterone.[17] The Johnson total synthesis of progesterone.[18] A total synthesis of progesterone was reported in 1971 by W.S. Johnson (see figure to the right).[18] The synthesis begins with reacting the phosphonium salt 7 with phenyl lithium to produce the phosphonium ylide 8. The ylide 8 is reacted with an aldehyde to produce the alkene 9. The ketal protecting groups of 9 are hydrolyzed to produce the diketone 10, which in turn is cyclized to form the
cyclopentenone 11. The ketone of 11 is reacted with methyl lithium to yield the
tertiary alcohol 12, which in turn is treated with acid to produce the tertiary cation 13. The key step of the synthesis is the π-
cation cyclization of 13 in which the B-, C-, and D-rings of the steroid are
simultaneously formed to produce 14. This step resembles the cationic cyclization
reaction used in the biosynthesis of
steroids and hence is referred to as
biomimetic. In the next step the enol orthoester is hydrolyzed to produce the ketone 15. The cyclopentene A-ring is then opened by oxidizing with ozone to produce 16. Finally, the diketone 17 undergoes an intramolecular aldol condensation by treating with aqueous potassium hydroxide to produce progesterone.[18] Levels In women, progesterone levels are
relatively low during the preovulatory
phase of the menstrual cycle, rise after ovulation, and are elevated during the luteal phase, as shown in diagram below.
Progesterone levels tend to be < 2 ng/ml
prior to ovulation, and > 5 ng/ml after
ovulation. If pregnancy occurs, human chorionic gonadotropin is released maintaining the corpus leuteum allowing it
to maintain levels of progesterone. At
around 12 weeks the placenta begins to
produce progesterone in place of the
corpus leuteum, this process is named the
luteal-placental shift. After the luteal- placental shift progesterone levels start to
rise further and may reach 100-200 ng/ml
at term. Whether a decrease in
progesterone levels is critical for the
initiation of labor has been argued and may be species-specific. After delivery of
the placenta and during lactation,
progesterone levels are very low. Progesterone levels are relatively low in children and postmenopausal women.[19] Adult males have levels similar to those in
women during the follicular phase of the
menstrual cycle. Person type Reference range for blood test Lower limit Upper limit Unit Female -
menstrual cycle (see diagram below) Female -
mL 1.1[21] 2.9[21] nmol/
L Males ≥16 years 0.27[20] 0.9[20] ng/
mL 0.86[21] 2.9[21] nmol/
L Female or male
1-9 years 0.1[20] 4.1[20] or 4.5[20] ng/
mL 0.3[21] 13[21] nmol/
L Progesterone levels during the menstrual cycle.[22] - The ranges denoted By biological stage may be used in closely monitored menstrual cycles in regard to other markers of its biological progression, with the time scale being compressed or stretched to how much faster or slower, respectively, the cycle progresses compared to an average cycle. - The ranges denoted Inter-cycle variability are more appropriate to use in non-monitored cycles with only the beginning of menstruation known, but where the woman accurately knows her average cycle lengths and time of ovulation, and that they are somewhat averagely regular, with the time scale being compressed or stretched to how much a woman's average cycle length is shorter or longer, respectively, than the average of the population. - The ranges denoted Inter-woman variability are more appropriate to use when the average cycle lengths and time of ovulation are unknown, but only the beginning of menstruation is given. Effects Micrograph showing changes to the endometrium due to progesterone (decidualization) H&E stain. Progesterone exerts its primary action
through the intracellular progesterone receptor although a distinct, membrane bound progesterone receptor has also been postulated.[23][24] In addition, progesterone is a highly potent antagonist
of the mineralocorticoid receptor (MR, the receptor for aldosterone and other mineralocorticosteroids). It prevents MR
activation by binding to this receptor with
an affinity exceeding even those of
aldosterone and other corticosteroids such as cortisol and corticosterone.[25] Progesterone has a number of
physiological effects that are amplified in
the presence of estrogen. Estrogen through estrogen receptors upregulates the expression of progesterone receptors.[26] Also, elevated levels of progesterone
potently reduce the sodium-retaining
activity of aldosterone, resulting in
natriuresis and a reduction in extracellular
fluid volume. Progesterone withdrawal, on
the other hand, is associated with a temporary increase in sodium retention
(reduced natriuresis, with an increase in
extracellular fluid volume) due to the
compensatory increase in aldosterone
production, which combats the blockade of
the mineralocorticoid receptor by the previously elevated level of progesterone. [27] Reproductive system Progesterone has key effects via non-
genomic signalling on human sperm as
they migrate through the female tract
before fertilization occurs, though the receptor(s) as yet remain unidentified.[28] Detailed characterisation of the events
occurring in sperm in response to
progesterone has elucidated certain events
including intracellular calcium transients and maintained changes,[29] slow calcium oscillations,[30] now thought to possibly regulate motility.[31] Interestingly progesterone has also been shown to
demonstrate effects on octopus spermatozoa.[32] Progesterone modulates the activity of CatSper (cation channels of sperm) voltage- gated Ca2+ channels. Since eggs release progesterone, sperm may use progesterone
as a homing signal to swim toward eggs
(chemotaxis). Hence substances that block the progesterone binding site on CatSper
channels could potentially be used in male contraception.[33][34] Progesterone is sometimes called the "hormone of pregnancy",[35] and it has many roles relating to the development of
the fetus: Progesterone converts the endometrium to its secretory stage to prepare the
uterus for implantation. At the same
time progesterone affects the vaginal epithelium and cervical mucus, making it thick and impenetrable to sperm. If pregnancy does not occur, progesterone
levels will decrease, leading, in the
human, to menstruation. Normal menstrual bleeding is progesterone-
withdrawal bleeding. If ovulation does
not occur and the corpus luteum does
not develop, levels of progesterone may
be low, leading to anovulatory dysfunctional uterine bleeding. During implantation and gestation, progesterone appears to decrease the
maternal immune response to allow for the acceptance of the pregnancy. Progesterone decreases contractility of the uterine smooth muscle.[35] In addition progesterone inhibits lactation during pregnancy. The fall in progesterone levels following delivery
is one of the triggers for milk
production. A drop in progesterone levels is possibly
one step that facilitates the onset of labor. The fetus metabolizes placental progesterone in the production of adrenal steroids. Nervous system Progesterone, like pregnenolone and dehydroepiandrosterone, belongs to the group of neurosteroids. It can be synthesized within the central nervous system and also serves as a precursor to another major neurosteroid, allopregnanolone. Neurosteroids affect synaptic functioning, are neuroprotective, and affect myelination.[36] They are investigated for their potential to improve memory and cognitive ability. Progesterone affects regulation of apoptotic genes. Its effect as a neurosteroid works
predominantly through the GSK-3 beta pathway, as an inhibitor. (Other GSK-3 beta
inhibitors include bipolar mood stabilizers, lithium and valproic acid.) Other syndromes It raises epidermal growth factor-1 levels, a factor often used to induce
proliferation, and used to sustain
cultures, of stem cells. It increases core temperature
(thermogenic function) during ovulation. [37] It reduces spasm and relaxes smooth muscle. Bronchi are widened and mucus regulated. (Progesterone receptors are widely present in submucosal tissue.) It acts as an antiinflammatory agent and regulates the immune response. It reduces gall-bladder activity. [38] It normalizes blood clotting and vascular tone, zinc and copper levels, cell oxygen levels, and use of fat stores for energy. It may affect gum health, increasing risk
of gingivitis (gum inflammation) and
tooth decay. It appears to prevent endometrial cancer (involving the uterine lining) by regulating the effects of estrogen. Adverse effects Pill form of progesterone (actually a
synthetic version such as Progestogen)
taken at 400 mg as cited by the following
patent can cause increased fluid retention,
which may result in epilepsy, migraine, asthma, cardiac or renal dysfunction. Blood
clots that can result in strokes and heart
attacks, which may lead to death or long-
term disability, may develop; pulmonary
embolus or breast cancer can also develop as a result of progesterone therapy.
Progesterone is associated with an
increased risk of thrombotic disorders such
as thrombophlebitis, cerebrovascular disorders, pulmonary embolism, and retinal thrombosis.[39] Common adverse effects include cramps,
abdominal pain, skeletal pain, perineal
pain, headache, arthralgia, constipation, dyspareunia, nocturia, diarrhea, nausea, vomiting, breast enlargement, joint pain,
flatulence, hot flushes, decreased libido,
thirst, increased appetite, nervousness, drowsiness, excessive urination at night.
Psychiatric effects including depression, mood swings, emotional instability,
aggression, abnormal crying, insomnia, forgetfulness, sleep disorders.[39] Less frequent adverse effects that may
occur include allergy, anemia, bloating,
fatigue, tremor, urticaria, pain, conjunctivitis, dizziness, vomiting,
myalgia, back pain, breast pain, genital
itching, genital yeast infection, upper
respiratory tract infection, cystitis, dysuria, asthenia, xerophthalmia, syncope, dysmenorrhea, premenstrual tension, gastritis, urinary tract infection, vaginal discharge, pharyngitis, sweating, hyperventilation, vaginal dryness, dyspnea, fever, edema, flu-like symptoms, dry mouth, rhinitis, leg pain, skin
discoloration, skin disorders, seborrhea, sinusitis, acne.[39] Current research suggests that
progesterone plays an important role in the
signaling of insulin release and pancreatic
function, and may affect the susceptibility to diabetes.[40] It has been shown that women with high levels of progesterone
during pregnancy are more likely to develop glucose abnormalities.[41] Medical applications Prometrium 100 mg Oral Capsule The use of progesterone and its analogues
have many medical applications, both to
address acute situations and to address the
long-term decline of natural progesterone
levels. Because of the poor bioavailability
of progesterone when taken orally, many synthetic progestins have been designed with improved oral bioavailability. [42] Progesteone was approved by the United
States Food and Drug Administration as vaginal gel on July 31, 1997,[43] an oral capsule on May 14, 1998[44] in an injection form on April 25, 2001[45] and as a vaginal insert on June 21, 2007.[46] In Italy and Spain, Progesterone is sold under the
trademark Progeffik. Bioavailability The route of administration impacts the
effect of the drug. Given orally,
progesterone has a wide person-to-person
variability in absorption and bioavailability while synthetic progestins are rapidly absorbed with a longer half-life than progesterone and maintain stable levels in the blood.[47] Progesterone does not dissolve in water
and is poorly absorbed when taken orally
unless micronized in oil. Products are often sold as capsules containing micronised progesterone in oil. Progesterone can also
be administered through vaginal or rectal suppositories or pessaries, transdermally through a gel or cream,[48] or via injection (though the latter has a short half-life requiring daily administration). "Natural progesterone" products derived
from yams do not require a prescription, but there is no evidence that the human
body can convert its active ingredient
(diosgenin, the plant steroid that is chemically converted to produce progesterone industrially[16]) into progesterone.[49][50] Specific uses Progesterone is used to support
pregnancy in Assisted Reproductive
Technology (ART) cycles such as In-vitro
Fertilization (IVF). While daily
intramuscular injections of
progesterone-in-oil (PIO) have been the standard route of administration, PIO
injections are not FDA-approved for use
in pregnancy. A recent meta-analysis
showed that the intravaginal route with
an appropriate dose and dosing
frequency is equivalent to daily intramuscular injections.[51] In addition, a recent case-matched study comparing
vaginal progesterone with PIO
injections showed that live birth rates
were nearly identical with both methods.[52] Progesterone is used to control
persistent anovulatory bleeding. It is
also used to prepare uterine lining in infertility therapy and to support early pregnancy. Patients with recurrent pregnancy loss due to inadequate progesterone production may receive
progesterone. Progesterone is also used in
nonpregnant women with a delayed
menstruation of one or more weeks, in
order to allow the thickened
endometrial lining to slough off. This
process is termed a progesterone withdrawal bleed. The progesterone is
taken orally for a short time (usually one
week), after which the progesterone is
discontinued and bleeding should occur. Progesterone is being investigated as
potentially beneficial in treating multiple sclerosis, since the characteristic deterioration of nerve myelin insulation halts during pregnancy, when progesterone levels
are raised; deterioration commences
again when the levels drop. Vaginally dosed progesterone is being
investigated as potentially beneficial in
preventing preterm birth in women at
risk for preterm birth. The initial study
by Fonseca suggested that vaginal
progesterone could prevent preterm birth in women with a history of preterm birth.[53] According to a recent study, women with a short cervix that
received hormonal treatment with a
progesterone gel had their risk of
prematurely giving birth reduced. The
hormone treatment was administered
vaginally every day during the second half of a pregnancy. [54] A subsequent and larger study showed that
vaginal progesterone was no better than
placebo in preventing recurrent preterm
birth in women with a history of a previous preterm birth,[55] but a planned secondary analysis of the data in this trial
showed that women with a short cervix at
baseline in the trial had benefit in two
ways: a reduction in births less than 32
weeks and a reduction in both the
frequency and the time their babies were in intensive care.[56] In another trial, vaginal progesterone was shown to be
better than placebo in reducing preterm
birth prior to 34 weeks in women with an extremely short cervix at baseline. [57] An editorial by Roberto Romero discusses the
role of sonographic cervical length in
identifying patients who may benefit from progesterone treatment.[58] Progesterone also has a role in skin
elasticity and bone strength, in respiration, in nerve tissue and in female sexuality, and the presence of progesterone receptors in certain muscle
and fat tissue may hint at a role in sexually-dimorphic proportions of those. [59] Progesterone receptor antagonists, or selective progesterone receptor
modulators (SPRM)s, such as RU-486 (Mifepristone), can be used to prevent conception or induce medical abortions. Note that methods of hormonal contraception do not contain progesterone but a progestin. Progesterone may affect male behavior. [60] Progesterone is starting to be used in the
treatment of the skin condition hidradenitis suppurativa.[citation needed] Aging Since most progesterone in males is
created during testicular production of testosterone, and most in females by the ovaries, the shutting down (whether by natural or chemical means), or removal, of
those inevitably causes a considerable
reduction in progesterone levels. Previous
concentration upon the role of progestagens (progesterone and molecules with similar effects) in female
reproduction, when progesterone was
simply considered a "female hormone",
obscured the significance of progesterone
elsewhere in both sexes. The tendency for progesterone to have a
regulatory effect, the presence of
progesterone receptors in many types of body tissue, and the pattern of
deterioration (or tumor formation) in many of those increasing in later years when
progesterone levels have dropped, is
prompting widespread research into the
potential value of maintaining
progesterone levels in both males and
females. Brain damage Previous studies have shown that
progesterone supports the normal
development of neurons in the brain, and
that the hormone has a protective effect
on damaged brain tissue. It has been
observed in animal models that females have reduced susceptibility to traumatic brain injury and this protective effect has been hypothesized to be caused by
increased circulating levels of estrogen and progesterone in females.[61] A number of additional animal studies have confirmed
that progesterone has neuroprotective
effects when administered shortly after traumatic brain injury.[62] Encouraging results have also been reported in human clinical trials.[63][64] The mechanism of progesterone protective
effects may be the reduction of
inflammation that follows brain trauma.
ESTROGENS
Estrogens (AmE), oestrogens (BE), or œstrogens, are a group of compounds named for their importance in the estrous cycle of humans and other animals. They are the primary female sex hormones. Natural estrogens are steroid hormones, while some synthetic ones are non-
steroidal. Their name comes from the Greek words estrus/οίστρος = sexual desire + gen/γόνο = to generate. Estrogens are synthesized in all vertebrates[1] as well as some insects.[2] Their presence in both vertebrates and
insects suggests that estrogenic sex
hormones have an ancient evolutionary
history. Estrogens are used as part of some oral contraceptives, in estrogen replacement therapy for postmenopausal women, and in hormone replacement therapy for trans women. Like all steroid hormones, estrogens
readily diffuse across the cell membrane. Once inside the cell, they bind to and
activate estrogen receptors which in turn modulate the expression of many genes.[3] Additionally, estrogens have been shown
to activate a G protein-coupled receptor, GPR30.[4] Types Steroidal The three major naturally occurring
estrogens in women are estrone (E1), estradiol (E2), and estriol (E3). Estrone is produced during menopause,
estradiol is the predominant form in
nonpregnant females, and estriol is the
primary estrogen of pregnancy. In the body these are all produced from androgens through actions of enzymes.[citation needed] From menarche to menopause the primary estrogen is estradiol. In
postmenopausal women the primary
estrogen is estrone. The enzyme aromatase converts testosterone to estradiol. Aromatase also converts androstenedione to estrone. Estrone is weaker than estradiol.[citation needed] Premarin, a commonly prescribed estrogenic drug, contains the steroidal
estrogens equilin and equilenin. There are oestradiol skin patches such as Estraderm
(the original brand, introduced in the late
1980s) that offer a completely natural
alternative. (A skin patch rather than pill
also has the advantage of direct
transmission into the blood stream without going through the liver.)[citation needed] Reference ranges for the blood content of estradiol, the primary type of estrogen, during the menstrual cycle.[5] Nonsteroidal A range of synthetic and natural
substances have been identified that also possess estrogenic activity. [6] Synthetic substances of this kind are
known as xenoestrogens. Plant products with estrogenic activity
are called phytoestrogens. Those produced by fungi are known as mycoestrogens. Unlike estrogens produced by mammals,
these substances are not necessarily steroids. Biosynthesis Steroidogenesis, showing estrogens at bottom right as in pink triangle. Estrogens are produced primarily by
developing follicles in the ovaries, the corpus luteum, and the placenta. Luteinizing hormone (LH) stimulates the production of estrogen in the ovaries. Some estrogens are also produced in
smaller amounts by other tissues such as
the liver, adrenal glands, and the breasts. These secondary sources of estrogens are
especially important in postmenopausal women. Fat cells also produce estrogen,[7] potentially the reason why being underweight or overweight are risk factors for infertility.[8] In females, synthesis of estrogens starts in theca interna cells in the ovary, by the synthesis of androstenedione from cholesterol. Androstenedione is a substance of moderate androgenic activity.
This compound crosses the basal membrane into the surrounding granulosa cells, where it is converted to oestrone or oestradiol, either immediately or through
testosterone. The conversion of
testosterone to oestradiol, and of
androstenedione to oestrone, is catalyzed
by the enzyme aromatase. Oestradiol levels vary through the
menstrual cycle, with levels highest just
before ovulation. Function The actions of estrogen are mediated by
the Estrogen receptor (ER), a dimeric nuclear protein that binds to DNA and
controls gene expression. Like other steroid
hormones, estrogen enters passively into
the cell where it binds to and activates the
estrogen receptor. The estrogen:ER complex
binds to specific DNA sequences called a Hormone response element to activate the transcription of some 137 ER-regulated
genes, of which 89 are direct target genes. [9] Since estrogen enters all cells, its action are dependent on the presence of the ER in
the cell. The ER is expressed in specific
tissues including the ovary, uterus and
breast. While estrogens are present in both men and women, they are usually present at significantly higher levels in women of
reproductive age. They promote the
development of female secondary sexual characteristics, such as breasts, and are also involved in the thickening of the endometrium and other aspects of regulating the menstrual cycle. In males, estrogen regulates certain functions of the reproductive system important to the maturation of sperm[10][11][12] and may be necessary for a healthy libido. [13][14] Furthermore, there are several other
structural changes induced by estrogen in
addition to other functions. Structural promote formation of female secondary sex characteristics accelerate metabolism reduce muscle mass increase fat stores stimulate endometrial growth increase uterine growth increase vaginal lubrication thicken the vaginal wall maintenance of vessel and skin reduce bone resorption, increase bone formation morphic change (endomorphic -> mesomorphic -> ectomorphic) protein synthesis increase hepatic production of binding proteins coagulation increase circulating level of factors 2, 7, 9, 10, plasminogen decrease antithrombin III increase platelet adhesiveness Lipid increase HDL, triglyceride decrease LDL, fat deposition Fluid balance salt (sodium) and water retention increase cortisol, SHBG Gastrointestinal tract reduce bowel motility increase cholesterol in bile Melanin increase pheomelanin, reduce eumelanin Cancer support hormone-sensitive breast cancers (see section below) Lung function promotes lung function by supporting alveoli (in rodents but probably in humans).[15] Sexual desire is dependent on androgen levels rather than estrogen levels. [16] Fetal development In mice, estrogens (which are locally
aromatized from androgens in the brain)
play an important role in psychosexual
differentiation, for example, by masculinizing territorial behavior;[17] the same is not true in humans.[18] In humans, the masculinizing effects of prenatal
androgens on behavior (and other tissues,
with the possible exception of effects on
bone) appear to act exclusively through the androgen receptor.[19] As a result, the utility of rodent models for studying
human psychosexual differentiation has been questioned.[20] Mental health Estrogen is considered to play a significant
role in women’s mental health. Sudden estrogen withdrawal, fluctuating estrogen,
and periods of sustained estrogen low levels correlates with significant mood
lowering. Clinical recovery from postpartum, perimenopause, and postmenopause depression has been shown to be effective after levels of
estrogen were stabilized and/or restored. [21][22] Low estrogen levels in male lab mice may
be one cause of obsessive–compulsive disorder (OCD). When estrogen levels were raised through the increased activity of the
enzyme aromatase in male lab mice, OCD rituals were dramatically decreased. Hypothalamic protein levels in the gene COMT are enhanced by increasing estrogen levels which is believed to return mice that
displayed OCD rituals to normal activity.
Aromatase deficiency is ultimately
suspected which is involved in the
synthesis of estrogen in humans and has
therapeutic implications in humans having obsessive-compulsive disorder. [23] Medical applications Oral contraceptives Since estrogen circulating in the blood can negatively feed-back to reduce circulating levels of FSH and LH, most oral contraceptives contain a synthetic
estrogen, along with a synthetic progestin. Even in men, the major hormone involved
in LH feedback is estradiol, not testosterone. Hormone replacement therapy As more fully discussed in the article on Hormone replacement therapy, estrogen and other hormones are given to postmenopausal women in order to prevent osteoporosis as well as treat the symptoms of menopause such as hot
flushes, vaginal dryness, urinary stress
incontinence, chilly sensations, dizziness,
fatigue, irritability, and sweating.
Fractures of the spine, wrist, and hips
decrease by 50-70% and spinal bone density increases by ~5% in those women
treated with estrogen within 3 years of
the onset of menopause and for 5–10 years
thereafter. Before the specific dangers of conjugated
equine estrogens were well understood,
standard therapy was 0.625 mg/day of
conjugated equine estrogens (such as
Premarin). There are, however, risks
associated with conjugated equine estrogen therapy. Among the older
postmenopausal women studied as part of
the Women's Health Initiative (WHI), an orally administered conjugated equine
estrogen supplement was found to be
associated with an increased risk of
dangerous blood clotting. The WHI studies used one type of estrogen supplement, a
high oral dose of conjugated equine
estrogens (Premarin alone and with medroxyprogesterone acetate as PremPro). [24] In a study by the NIH, esterified estrogens
were not proven to pose the same risks to
health as conjugated equine estrogens. Hormone replacement therapy has favorable effects on serum cholesterol
levels, and when initiated immediately
upon menopause may reduce the incidence
of cardiovascular disease, although this
hypothesis has yet to be tested in
randomized trials. Estrogen appears to have a protector effect on atherosclerosis :
it lowers LDL and triglycerides, it raises
HDL levels and has endothelial
vasodilatation properties plus an anti-
inflammatory component. Research is underway to determine if risks
of estrogen supplement use are the same
for all methods of delivery. In particular,
estrogen applied topically may have a different spectrum of side-effects than when administered orally, [25] and transdermal estrogens do not affect
clotting as they are absorbed directly into
the systemic circulation, avoiding first-pass
metabolism in the liver. This route of
administration is thus preferred in women
with a history of thrombo-embolic disease. Estrogen is also used in the therapy of
vaginal atrophy, hypoestrogenism (as a
result of hypogonadism, castration, or
primary ovarian failure), amenorrhea,
dysmenorrhea, and oligomenorrhea.
Estrogens can also be used to suppress lactation after child birth. Breast cancer About 80% of breast cancers, once
established, rely on supplies of the
hormone estrogen to grow: they are
known as hormone-sensitive or hormone-
receptor-positive cancers. Suppression of
production of estrogen in the body is a treatment for these cancers. Recently researchers have discovered that
the common table mushroom has anti- aromatase[26] properties and therefore possible anti-estrogen activity. Clinical
trials have begun in the United States looking into whether the table mushroom can prevent breast cancer in people.[27] A recent study has highlighted the
importance of this research. In 2009, a
case-control study of the eating habits of
2,018 women, revealed that women who
consumed mushrooms had an
approximately 50% lower incidence of breast cancer. Women who consumed mushrooms and green tea had a 90% lower incidence of breast cancer.[28] Hormone-receptor-positive breast cancers
are treated with drugs which suppress production of estrogen in the body.[29] This technique, in the context of treatment of
breast cancer, is known variously as hormonal therapy, hormone therapy, or anti-estrogen therapy (not to be confused with hormone replacement therapy).
Certain foods such as soy may also
suppress the proliferative effects of
estrogen and are used as an alternative to hormone therapy.[30] Prostate cancer Under certain circumstances, estrogen may
also be used in males for treatment of prostate cancer.[31] Miscellaneous In humans and mice, estrogen promotes wound healing.[32] At one time, estrogen was used to induce growth attenuation in tall girls.[33] Recently, estrogen-induced growth
attenuation was used as part of the
controversial Ashley Treatment to keep a developmentally disabled girl from growing to adult size.[34] Most recently, estrogen has been used in
experimental research as a way to treat
patients suffering from bulimia nervosa, in addition to Cognitive Behavioral Therapy , which is the established standard for
treatment in bulimia cases. The estrogen
research hypothesizes that the disease
may be linked to a hormonal imbalance in the brain.[35] Estrogen has also been used in studies
which indicate that it may be an effective
drug for use in the treatment of traumatic liver injury. [36] Health risks and warning labels Hyperestrogenemia (elevated levels of
estrogen) may be a result of exogenous
administration of estrogen or estrogen-like
substances, or may be a result of
physiologic conditions such as pregnancy.
Any of these causes is linked with an increase in the risk of thrombosis.[37] The estrogen-alone substudy of the WHI
reported an increased risk of stroke and deep vein thrombosis (DVT) in postmenopausal women 50 years of age or
older and an increased risk of dementia in postmenopausal women 65 years of age or
older using 0.625 mg of Premarin
conjugated equine estrogens (CEE). The
estrogen-plus-progestin substudy of the
WHI reported an increased risk of myocardial infarction, stroke, invasive breast cancer, pulmonary emboli and DVT in postmenopausal women 50 years of age
or older and an increased risk of dementia
in postmenopausal women 65 years of age
or older using PremPro, which is 0.625 mg
of CEE with 2.5 mg of the progestin medroxyprogesterone acetate (MPA).[38] [39][40] The labeling of estrogen-only products in
the U.S. includes a boxed warning that unopposed estrogen (without progestagen) therapy increases the risk of endometrial cancer. Based on a review of data from the WHI, on January 8, 2003 the
FDA changed the labeling of all estrogen
and estrogen with progestin products for
use by postmenopausal women to include
a new boxed warning about cardiovascular
and other risks. Cosmetics Some hair shampoos on the market include estrogens and placental extracts; others
contain phytoestrogens. There are case
reports of young children developing
breasts after exposure to these shampoos. [41] On September 9, 1993, the FDA determined that not all topically applied
hormone-containing drug products for OTC human use are generally recognized as safe and effective and are misbranded. An accompanying proposed rule deals with
cosmetics, concluding that any use of
natural estrogens in a cosmetic product
makes the product an unapproved new
drug and that any cosmetic using the term
"hormone" in the text of its labeling or in its ingredient statement makes an implied
drug claim, subjecting such a product to regulatory action.[42] In addition to being considered
misbranded drugs, products claiming to
contain placental extract may also be
deemed to be misbranded cosmetics if the
extract has been prepared from placentas
from which the hormones and other biologically active substances have been
removed and the extracted substance
consists principally of protein. The FDA
recommends that this substance be
identified by a name other than "placental
extract" and describing its composition more accurately because consumers
associate the name "placental extract"
with a therapeutic use of some biological activity. [42] History In 1929 Adolf Butenandt and Edward Adelbert Doisy independently isolated and determined the structure of estrogen.[43] Thereafter, the market for hormonal drug
research opened up. The “first orally effective estrogen”,
Emmenin, derived from the late-pregnancy
urine of Canadian women, was introduced
in 1930 by Collip and Ayerst Laboratories.
Estrogens are not water-soluble and cannot
be given orally, but the urine was found to contain estriol glucuronide which is water soluble and becomes active in the body
after hydrolization. Scientists continued to search for new
sources of estrogen because of concerns
associated with the practicality of
introducing the drug into the market. At
the same time, a German pharmaceutical
drug company, formulated a similar product as Emmenin that was introduced
to German women to treat menopausal
symptoms. In 1938, British scientists obtained a patent
on a newly formulated nonsteroidal
estrogen, diethylstilbestrol (DES), that was cheaper and more powerful than the
previously manufactured estrogens. Soon
after, concerns over the side effects of DES
were raised in scientific journals while the
drug manufacturers came together to lobby
for governmental approval of DES. It was only until 1941 when estrogen therapy
was finally approved by the Food and Drug
Administration (FDA) for the treatment of menopausal symptoms.[44] Environmental effects Estrogens are among the wide range of
endocrine-disrupting compounds (EDCs) because they have high estrogenic
potency. When this specific EDC makes its
way into the environment it may cause
male reproductive dysfunction to wildlife. [45] The estrogen excreted from farm animals makes its way into fresh water systems.[46] During the germination period of reproduction the fish are exposed to low
levels of estrogen which may cause reproductive dysfunction to male fish.
INTERNAL ILIAC ARTERY
The internal iliac artery (formerly known as the hypogastric artery) is the main artery of the pelvis. Structure The internal iliac artery supplies the walls
and viscera of the pelvis, the buttock, the reproductive organs, and the medial compartment of the thigh. It is a short, thick vessel, smaller than the external iliac artery, and about 3 to 4 cm in length. Course It arises at the bifurcation of the common iliac artery, opposite the lumbosacral articulation, and, passing downward to the
upper margin of the greater sciatic foramen, divides into two large trunks, an anterior and a posterior. The following are relations of the artery at
various points: it is posterior to the ureter, anterior to the internal iliac vein, the lumbosacral trunk, and the piriformis muscle; near its origin, it is medial to the external iliac vein, which lies between it and the psoas major muscle; it is above the obturator nerve. Branches The exact arrangement of branches of the
internal iliac artery is variable. Generally,
the artery divides into an anterior division
and a posterior division, with the posterior
division giving rise to the superior gluteal,
iliolumbar, and lateral sacral arteries. The rest usually arise from the anterior
division. The following are the branches of internal
iliac artery. Because it is variable, a listed
artery may not be a direct branch, but
instead might arise off a direct branch. Division Branch Sub- branches To/ through Posterior Iliolumbar
artery lumbar
and iliac
branches psoas
major
muscle, quadratus
lumborum
muscle, iliacus
muscle Posterior Lateral
sacral
arteries superior
and
inferior
branches anterior
sacral
foramina Posterior Superior
gluteal
artery - greater
sciatic
foramen Anterior Obturator
artery (occasionally
from inferior epigastric
artery) - obturator
canal Anterior Inferior
gluteal
artery - greater
sciatic
foramen Anterior Umbilical
artery superior
vesical
artery (usually,
but
sometimes
it branches
directly
from anterior
trunk) medial
umbilical
ligament Anterior Uterine
artery (females) or deferential
artery (males) superior
and
vaginal
branches uterus, vas
deferens Anterior Vaginal
artery (females,
can also
arise from uterine
artery) - vagina Anterior inferior
vesical
artery - urinary
bladder Anterior Middle rectal
artery - rectum Anterior Internal
pudendal
artery many
branches -
see article
for details greater
sciatic
foramen Right (distal from spectator) internal iliac artery and branches, except for iliolumbar artery, umbilical artery, uterine artery/deferential artery and vaginal artery/inferior vesical artery . Structure in fetus In the fetus, the internal iliac artery is twice as large as the external iliac, and is the direct continuation of the common iliac. It ascends along the side of the bladder, and runs upward on the back of the
anterior wall of the abdomen to the umbilicus, converging toward its fellow of the opposite side. Having passed through the umbilical
opening, the two arteries, now termed
umbilical, enter the umbilical cord, where they are coiled around the umbilical vein,
and ultimately ramify in the placenta. At birth, when the placental circulation
ceases, the pelvic portion only of the
umbilical artery remains patent gives rise
to the superior vesical artery (or arteries)
of the adult; the remainder of the vessel is
converted into a solid fibrous cord, the medial umbilical ligament (otherwise known as the obliterated hypogastric
artery) which extends from the pelvis to
the umbilicus. Variation In two-thirds of a large number of cases,
the length of the internal iliac varied
between 2.25 and 3.4 cm.; in the remaining
third it was more frequently longer than
shorter, the maximum length being about
7 cm. the minimum about 1 cm. The lengths of the common iliac and
internal iliac arteries bear an inverse
proportion to each other, the internal iliac
artery being long when the common iliac is
short, and vice versa. The place of division of the internal iliac
artery varies between the upper margin of
the sacrum and the upper border of the greater sciatic foramen. The right and left hypogastric arteries in a
series of cases often differed in length, but
neither seemed constantly to exceed the
other. Common branching variations The typical example [1] Collateral Circulation The circulation after ligature of the internal
iliac artery is carried on by the anastomoses of: the middle rectal artery and the superior rectal artery the iliolumbar artery with the last lumbar artery the lateral sacral arteries with the median sacral artery
URETER
In human anatomy, the ureters are muscular tubes that propel urine from the kidneys to the urinary bladder. In the adult, the ureters are usually 25–30 cm (10–12 in)
long and ~3-4 mm in diameter. In humans, the ureters arise from the renal pelvis on the medial aspect of each kidney before descending towards the bladder on
the front of the psoas major muscle. The ureters cross the pelvic brim near the bifurcation of the iliac arteries (which they
cross anteriorly). This is a common site for
the impaction of kidney stones (the others being the ureterovesical valve, where the
ureter meets the bladder, and the
pelviureteric junction, where the renal
pelvis meets the ureter in the renal hilum).
The ureters run posteroinferiorly on the
lateral walls of the pelvis and then curve anteriormedially to enter the bladder
through the back, at the vesicoureteric
junction, running within the wall of the
bladder for a few centimetres. The
backflow of urine is prevented by valves
known as ureterovesical valves. In females, the ureters pass through the mesometrium and under the uterine arteries on the way to the urinary bladder. Ureters are also found in all other amniote species, although different ducts fulfill the same role in amphibians and fish.[1] Disorders Cancer of the ureters is known as ureteral cancer. Clinical The ureter is sometimes injured in hysterectomies near the infundibulopelvic (suspensory) ligament or where the ureter courses posterior to the uterine vessels.
EXTERNAL ILIAC ARTERIES
The external iliac arteries are two major
arteries which bifurcate off the common iliac arteries anterior to the sacroiliac joint of the pelvis. They proceed anterior and
inferior along the medial border of the psoas major muscles. They exit the pelvic girdle posterior and inferior to the inguinal ligament about 1/3rd laterally from the insertion point of the inguinal ligament on
the pubic tubercle at which point they are referred to as the femoral arteries.[1]. The external iliac artery is usually the artery
used to attach the renal artery to the
recipient of a kidney transplant. Source Front of abdomen, showing common iliac artery, the source of the external iliac artery The external iliac artery arises from the
bifurcation of the common iliac artery. It travels inferiorly, anteriorly, and laterally,
making its ways to the lower limb: Branches Branch Description Inferior
epigastric
artery Goes upward to anastomose
with superior epigastric artery (a branch of internal thoracic artery). Deep
circumflex
iliac artery Goes laterally, travelling
along the iliac crest of the pelvic bone. femoral
artery Terminal branch. When the
external iliac artery passes
posterior to the inguinal ligament, its name changes to femoral artery.
OVARIAN FOSSA
The ovary lies in a shallow depression, named the ovarian fossa, on the lateral wall of the pelvis. This fossa has the following boundaries: superiorly: by the external iliac vessels anteriorly and inferiorly: by the broad ligament of the uterus posteriorly: by the ureter and internal iliac vessels
TESTES
The testicle (from Latin testiculus, diminutive of testis, meaning "witness" of virility,[1]plural testes) is the male gonad in animals. Like the ovaries to which they are homologous, testes are components of both the reproductive system and the endocrine system. The primary functions of the testes are to produce sperm (spermatogenesis) and to produce androgens, primarily testosterone. Both functions of the testicle are influenced
by gonadotropic hormones produced by the
anterior pituitary. Luteinizing hormone (LH) results in testosterone release. The
presence of both testosterone and follicle- stimulating hormone (FSH) is needed to support spermatogenesis. Anatomy and physiology External appearance Almost all healthy male vertebrates have two testes. They are typically of similar
size, although in sharks, that on the right side is usually larger, and in many bird and
mammal species, the left may be the
larger. The primitive jawless fish have only a single testis, located in the midline of the
body, although even this forms from the
fusion of paired structures in the embryo. [2] In mammals, the testes are often contained within an extension of the abdomen called the scrotum. In mammals with external testes it is most common for
one testicle to hang lower than the other.
While the size of the testicle varies, it is
estimated that 21.9% of men have their
higher testicle being their left, while
27.3% of men have reported to have equally positioned testicles.[3] This is due to differences in the vascular anatomical
structure on the right and left sides. In healthy European adult human males,
average testicular volume is 18 cm³ per
testis, with normal size ranging from 12 cm³ to 30 cm³.[4] The average testicle size after puberty measures up to around
2 inches long, 0.8 inches in breadth, and
1.2 inches in height (5 x 2 x 3 cm).
Measurement in the living adult is done in
two basic ways: comparing the testicle with ellipsoids of known sizes (orchidometer). measuring the length, depth and width
with a ruler, a pair of calipers or ultrasound imaging. The volume is then calculated using the
formula for the volume of an ellipsoid: 4/3 π × (length/2) × (width/2) × (depth/2). Internal structure Transverse section through
the left side of the scrotum and the left testis. Cross section of rabbit testis, magnified 40 times. Duct system Under a tough membranous shell, the tunica albuginea, the testis of amniotes and some teleost fish, contains very fine coiled tubes called seminiferous tubules. The tubules are lined with a layer of cells
(germ cells) that from puberty into old age, develop into sperm cells (also known as spermatozoa or male gametes). The developing sperm travel through the
seminiferous tubules to the rete testis located in the mediastinum testis, to the efferent ducts, and then to the epididymis where newly-created sperm cells mature
(see spermatogenesis). The sperm move into the vas deferens, and are eventually expelled through the urethra and out of the urethral orifice through muscular contractions. Amphibians and most fish do not possess seminiferous tubules. Instead, the sperm
are produced in spherical structures called
sperm ampullae. These are seasonal
structures, releasing their contents during
the breeding season, and then being
reabsorbed by the body. Before the next breeding season, new sperm ampullae
begin to form and ripen. The ampullae are
otherwise essentially identical to the
seminiferous tubules in higher vertebrates, including the same range of cell types.[2] Primary Cell Types Within the seminiferous tubules Here, germ cells develop into spermatogonia, spermatocytes, spermatids and spermatozoon through the process of spermatogenesis. The
gametes contain DNA for fertilization of an ovum[5] Sertoli cells - the true epithelium of the seminiferous epithelium, critical for the
support of germ cell development into
spermatozoa. Sertoli cells secrete inhibin.[6] Between tubules (interstitial cells) Leydig cells - cells localized between seminiferous tubules that produce and secrete testosterone and other androgens important for sexual development and puberty, secondary sexual characteristics like facial hair, sexual behavior and libido, supporting spermatogenesis and erectile function. Testosterone also controls testicular
volume. Also present are: Immature Leydig cells Interstitial macrophages and epithelial cells. Blood supply and lymphatic drainage Blood supply and lymphatic drainage of the testes and scrotum are distinct: The paired testicular arteries arise directly from the abdominal aorta and descend through the inguinal canal, while the scrotum and the rest of the
external genitalia is supplied by the internal pudendal artery (itself a branch of the internal iliac artery). The testis has collateral blood supply
from 1. the cremasteric artery (a branch of the inferior epigastric artery, which is a branch of the external iliac artery), and 2. the artery to the ductus deferens (a branch of the inferior vesical artery , which is a branch of the internal iliac artery). Therefore, if the testicular artery is ligated, e.g., during a Fowler-
Stevens orchiopexy for a high undescended testis, the testis will
usually survive on these other blood
supplies. Lymphatic drainage of the testes
follows the testicular arteries back to
the paraaortic lymph nodes, while lymph from the scrotum drains to the inguinal lymph nodes. Layers Many anatomical features of the adult
testis reflect its developmental origin in
the abdomen. The layers of tissue enclosing each testicle are derived from the layers of
the anterior abdominal wall. Notably, the cremasteric muscle arises from the internal oblique muscle. The blood–testis barrier Large molecules cannot pass from the
blood into the lumen of a seminiferous
tubule due to the presence of tight junctions between adjacent Sertoli cells. The spermatogonia are in the basal
compartment (deep to the level of the tight
junctions) and the more mature forms such
as primary and secondary spermatocytes
and spermatids are in the adluminal
compartment. The function of the blood–testis barrier (red highlight in diagram above) may be to
prevent an auto-immune reaction. Mature sperm (and their antigens) arise long after immune tolerance is established in infancy.
Therefore, since sperm are antigenically
different from self tissue, a male animal
can react immunologically to his own
sperm. In fact, he is capable of making
antibodies against them. Injection of sperm antigens causes
inflammation of the testis (auto-immune
orchitis) and reduced fertility. Thus, the
blood–testis barrier may reduce the
likelihood that sperm proteins will induce
an immune response, reducing fertility and so progeny. Temperature regulation The testes work best at temperatures
slightly less than core body temperature.
The spermatogenesis is less efficient at lower and higher temperatures. This is
presumably why the testes are located
outside the body. There are a number of
mechanisms to maintain the testes at the
optimum temperature. Cremasteric muscle The cremasteric muscle is part of the spermatic cord. When this muscle contracts, the cord is shortened and the testicle is
moved closer up toward the body, which
provides slightly more warmth to maintain
optimal testicular temperature. When
cooling is required, the cremasteric muscle
relaxes and the testicle is lowered away from the warm body and is able to cool.
This phenomenon is known as the cremasteric reflex. It also occurs in response to stress (the testicles rise up
toward the body in an effort to protect
them in a fight). There are persistent
reports that relaxation indicates approach of orgasm.[citation needed] There is a noticeable tendency to also retract during
orgasm. The testicles can also be lifted voluntarily
using the pubococcygeus muscle, which partially activates related muscles. This can
sometimes be triggered by tightening or
sucking in the stomach or abdomen. This movement will also happen
spontaneously in some men when they
unintentionally contract their abdominal or
PC muscles. Development There are two phases in which the testes
grow substantially; namely in embryonic
and pubertal age. Embryonic During mammalian development, the
gonads are at first capable of becoming either ovaries or testes.[7] In humans, starting at about week 4 the gonadal
rudiments are present within the intermediate mesoderm adjacent to the developing kidneys. At about week 6, sex cords develop within the forming testes. These are made up of early Sertoli cells
that surround and nurture the germ cells that migrate into the gonads shortly before
sex determination begins. In males, the
sex-specific gene SRY that is found on the Y-chromosome initiates sex determination
by downstream regulation of sex-
determining factors, (such as GATA4, SOX9
and AMH), which leads to development of
the male phenotype, including directing
development of the early bipotential gonad down the male path of
development. Testes follow the "path of descent" from
high in the posterior fetal abdomen to the
inguinal ring and beyond to the inguinal canal and into the scrotum. In most cases (97% full-term, 70% preterm), both testes have descended by birth. In most other
cases, only one testis fails to descend
(cryptorchidism) and that will probabaly express itself within a year. Pubertal The testes grow in response to the start of spermatogenesis. Size depends on lytic function, sperm production (amount of
spermatogenisis present in testis), interstitial fluid, and Sertoli cell fluid production. After puberty, the volume of
the testes can be increased by over 500%
as compared to the pre-pubertal size.[citation needed] Testicles are fully descended before one reaches puberty. Evolution External testes The basal condition for mammals is to have
internal testes. Only the Boreoeutherian land mammals, the large group of
mammals that includes humans, have
externalized testes. Their testes function
best at temperatures lower than their core
body temperature. Their testes are located
outside of the body, suspended by the spermatic cord within the scrotum. The
testes of the non-boreotherian mammals
such as the monotremes, armadillos, sloths, elephants remain within the abdomen.[8] There are also some Boreoeutherian
mammals with internal testes, such as the
rhinoceros. Marine boreotherian mammals, such as
whales and dolphins, also have internal
testes, but it has recently been shown (e.g.,
for dolphins) that they use elaborate
vascular networks to provide the
necessary temperature lowering for optimum function. As external testes
would increase drag, many boreotherian
aquatic mammals have internal testes
which are kept cool by special circulatory
systems that cool the arterial blood going
to the testes by placing the arteries near veins bringing cooled venous blood from
the skin. There are several hypotheses why most
boreotherian mammals have external
testes which operate best at a
temperature that is slightly less than the
core body temperature, e.g. that it is stuck
with enzymes evolved in a colder temperature due to external testes
evolving for different reasons, that the
lower temperature of the testes simply is
more efficient for sperm production. 1) More efficient. The classic hypothesis is that cooler temperature of the testes
allows for more efficient fertile spermatogenesis. In other words, there are no possible enzymes operating at normal
core body temperature that are as efficient
as the ones evolved, at least none
appearing in our evolution so far. The early mammals had lower body
temperatures and thus their testes worked
efficiently within their body. However it is
argued that boreotherian mammals have
higher body temperatures than the other
mammals and had to develop external testes to keep them cool. It is argued that
those mammals with internal testes, such
as the monotremes, armadillos, sloths,
elephants, and rhinoceroses, have a lower
core body temperatures than those
mammals with external testes. However, the question remains why birds
despite having very high core body
temperatures have internal testes and did not evolve external testes. [9] It was once theorized that birds used their air sacs to cool the testes internally, but later studies
revealed that birds' testes are able to function at core body temperature.[9] Some mammals which have seasonal
breeding cycles keep their testes internal
until the breeding season at which point
their testes descend and increase in size and become external.[10] 2) Irreversible adaptation to sperm competition. It has been suggested that the ancestor of the boreoeutherian
mammals was a small mammal that
required very large testes (perhaps rather
like those of a hamster) for sperm competition and thus had to place its testes outside the body.[11] This led to enzymes involved in spermatogenesis,
spermatogenic DNA polymerase beta and
recombinase activities evolving a unique
temperature optimum, slightly less than
core body temperature. When the
boreoeutherian mammals then diversified into forms that were larger and/or did not
require intense sperm competition they
still produced enzymes that operated best
at cooler temperatures and had to keep
their testes outside the body. This position
is made less parsimonious by the fact that the kangaroo, a non-boreoeutherian mammal, has external testicles. The
ancestors of kangaroos might, separately
from boreotherian mammals, have also
been subject to heavy sperm competition
and thus developed external testes,
however, kangaroo external testes are suggestive of a possible adaptive function
for external testes in large animals. 3) Protection from abdominal cavity pressure changes. One argument for the evolution of external testes is that it
protects the testes from abdominal cavity
pressure changes caused by jumping and galloping.[12] Testicular size A human testicle is being measured with an orchidometer and is typically 15 to 25 ml in volume. Testicular size as a proportion of body
weight varies widely. In the mammalian
kingdom, there is a tendency for testicular
size to correspond with multiple mates
(e.g., harems, polygamy). Production of testicular output sperm and spermatic fluid
is also larger in polygamous animals, possibly a spermatogenic competition for survival. The testes of the right whale are likely to be the largest of any animal, each weighing around 500 kg (1,100 lb).[13] Testis weight also varies in seasonal
breeders like deer and horses. The change is related to changes in testosterone
production. Health issues Main article: Testicular disease Physical injury The testicles are well-known to be very
sensitive to impact and injury. The pain
involved travels up from each testicle
into the abdominal cavity, via the spermatic plexus, which is the primary nerve of each testicle. Testicular torsion ia a medical emergency. Treatment within 4-6 hours
of onset can prevent necrosis of the testis.[14] Testicular rupture is a medical emergency caused by blunt force
impact, sharp edge, or piercing impact
to one or both testicles, which can lead
to necrosis of the testis in as little as 30 minutes.[citation needed] Penetrating injuries to the scrotum may
cause castration, or physical separation or destruction of the testes, possibly
along with part or all of the penis, which
results in total sterility if the testicles
are not reattached quickly. Diseases and conditions that affect the
testes Some prominent conditions and
differential diagnoses include: Testicular cancer and other neoplasms To improve the chances of catching
possible cases of testicular cancer or other health issues early, regular testicular self-examination is recommended. Varicocele, swollen vein(s) from the testes, usually affecting the left side, [15] the testis usually being normal Hydrocele testis, swelling around testes caused by accumulation of clear liquid
within a membranous sac, the testis
usually being normal Endocrine disorders can also affect the size and function of the testis. Certain inherited conditions involving
mutations in key developmental genes
also impair testicular descent, resulting
in abdominal or inguinal testes which
remain nonfunctional and may become
cancerous. Other genetic conditions can result in the loss of the Wolffian ducts and allow for the persistence of Müllerian ducts. Bell Clapper Deformity is a deformity in
which the testicle is not attached to the
scrotal walls, and can rotate freely on
the spermatic cord within the tunica
vaginalis. This deformity has been
linked to Testicular torsion. Effects of exogenous hormones To some extent, it is possible to change
testicular size. Short of direct injury or
subjecting them to adverse conditions, e.g.,
higher temperature than they are normally accustomed to, they can be shrunk by
competing against their intrinsic hormonal
function through the use of externally
administered steroidal hormones. Steroids taken for muscle enhancement (especially anabolic steroids) often have the undesired side effect of testicular shrinkage. Similarly, stimulation of testicular
functions via gonadotropic-like hormones may enlarge their size. Testes may shrink
or atrophy during hormone replacement therapy or through chemical castration. In all cases, the loss in testes volume
corresponds with a loss of
spermatogenesis. Historical beliefs about testicles Main article: Sex selection In the Middle Ages, men who wanted a boy
sometimes had their left testicle removed.
This was because people believed that the
right testicle made "boy" sperm and the left made "girl" sperm.[16] As early as 330 BC, Aristotle prescribed the ligation (tying off) of the left testicle in men wishing to have boys. [17] Etymology The etymology of the word is based on Roman law. The Latin word "testis", witness, was used in the firmly established
legal principle "Testis unus, testis
nullus" (one witness [equals] no witness),
meaning that testimony by any one person
in court was to be disregarded unless
corroborated by the testimony of at least another. This led to the common practice of
producing two witnesses, bribed to testify
the same way in cases of lawsuits with
ulterior motives. Since such "witnesses"
always came in pairs, the meaning was
accordingly extended, often in the diminutive (testiculus, testiculi).[citation needed] Another theory says that testis is
influenced by a loan translation, from
Greek parastatēs "defender (in law),
supporter" that is "two glands side by side".[18] As a food Main article: Animelles Testicles of a male calf or other livestock
are used to comprise a dish, sometimes called Rocky Mountain oysters .
VERTEBRATES
Vertebrates (pronounced /ˈvɜrtɨbrəts/) are animals that are members of the subphylum Vertebrata (chordates with backbones and spinal columns). Vertebrates are the largest group of
chordates, with currently about 58,000 species described.[2] Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds. Extant vertebrates range in size from the carp species Paedocypris, at as little as 7.9 mm (0.3 inch), to the blue whale, at up to 33 m (110 ft). Vertebrates make up
about 5% of all described animal species;
the rest are invertebrates, which lack backbones. The vertebrates traditionally include the hagfishes, which do not have proper vertebrae, though their closest living
relatives, the lampreys, do have vertebrae. [3] Hagfishes do, however, possess a cranium. For this reason, the vertebrate subphylum is sometimes referred to as
"Craniata". Molecular analysis since 1999 has suggested that the hagfishes are most
closely related to lampreys, and so also are
vertebrates. Others consider them a sister
group of vertebrates in the common taxon of Craniata.[3][4] Etymology The word vertebrate derives from the
Latin word vertebratus ( Pliny), meaning joint of the spine.[5] It is closely related to the word vertebra, which refers to any of the bones or segments of the spinal column.[6] Anatomy and morphology All vertebrates are built along the basic
chordate body plan: a stiff rod running through the length of the animal (vertebral column or notochord),[7] with a hollow tube of nervous tissue (the spinal cord) above it and the gastrointestinal tract below. In all vertebrates, the mouth is
found at, or right below, the anterior end
of the animal, while the anus opens to the exterior before the end of the body. The
remaining part of the body continuing aft
of the anus forms a tail with vertebrae and spinal cord, but no gut.[8] The vertebral column The defining characteristic of a vertebrate
is the vertebral column, in which the notochord (a stiff rod of uniform composition) found in all chordates has been replaced by a segmented series of
stiffer elements (vertebrae) separated by
mobile joints (intervertebral discs, derived
embryonically and evolutionarily from the
notochord). However, a few vertebrates
have secondarily lost this anatomy, retaining the notochord into adulthood, such as the sturgeon[9] and the Latimeria. Jawed vertebrates are typified by paired appendages (fins or legs, which may be
secondarily lost), but this is not part of the
definition of vertebrates as a whole. Fossilized skeleton of Diplodocus, showing an extreme example of the backbone that characterizes the vertebrates. Exhibited at the Museum für Naturkunde (Museum of Natural Science), Berlin. Gills Gill arches bearing gills in a pike All basal vertebrates breathe with gills. The gills are carried right behind the head,
bordering the posterior margins of a series
of openings from the esophagus to the exterior. Each gill is supported by a cartilagenous or bony gill arch.[10] The bony fish have three pairs of arches, cartilaginous fish have five to seven pairs, while the primitive jawless fish have seven. The vertebrate ancestor no doubt
had more arches, as some of their chordate relatives have more than 50 pairs of gills. [8] In amphibians and some primitive bony fishes, the larvae bear external gills, branching off from the gill arches proper. [11] These are reduced in adulthood, their function taken over by the gills proper in
fishes and by lungs in most amphibians. Some amphibans retain the external larval
gills in adulthood, the complex internal gill
system as seen in fish apparently being
irrevocably lost very early in the evolution of tetrapods.[12] While the higher vertebrates do not have gills, the gill arches form during fetal developement, and lay the basis of essential structures such as jaws, the thyroid gland, the larynx, the columella (corresponding to the stapes in mammals) and in mammals the malleus and incus.[8] Central nervous system The vertebrates are the only chordate group to exhibit a proper brain. A slight swelling of the anterior end of the nerve
chord is found in the lancelet, though it lacks the eyes and other complex sense
organs comparable to those of vertebrates.
Other chordates do not show any trends towards cephalisation.[8] The central nervous system is based on a hollow nerve tube running along the length
of the animal, form which the peripheral nervous system branches out to enervate the various systems. The front end of the
nerve tube is expanded by a thickening of
the walls and expansion of the central canal of spinal cord into three primary brain vesicles: The prosencephalon (forebrain), mesencephalon (midbrain) and rhombencephalon (hindbrain), further differentiated in the various vertebrate groups.[13] Two laterally placed eyes form around outgrows from the midbrain,
except in hagfish, though this may be a secondary loss.[14][15] The forebrain is well developed and subdivided in most tetrapods, while the midbrain dominate in many fish and some salamanders. Vesicles of the forebrain are usually paired, giving
rise to hemispheres like the cerebral hemispheres in mammals.[13] The resulting anatomy of the central nervous system,
with a single, hollow nerve chord topped
by a series of (often paired) vesicles is
unique to vertebrates. All invertebrates with well developed brains, like insects, spiders and squids have a ventral rather than dorsal system of ganglions, with a split brain stem running on each side of the mouth/gut.[8] Evolutionary history The first vertebrates Vertebrates originated about 525 million
years ago during the Cambrian explosion, which saw the rise in organism diversity.
The earliest known vertebrate is believed to be the Myllokunmingia.[1] Another early vertebrate is Haikouichthys ercaicunensis. Unlike the other fauna that dominated the
Cambrian, these groups had the basic
vertebrate body plan: a notochord,
rudimentary vertebrae, and a well-defined head and tail.[16] All of these early vertebrates lacked jaws in the common sense and relied on filter feeding close to the seabed.[17] From fishes to amphibians The first jawed vertebrates appeared in the Ordovician and became common in the Devonian, often known as the "Age of Fishes".[18] The two groups of bony fishes, the actinopterygii and sarcopterygii, evolved and became common. [19] The Devonian also saw the demise of virtually
all jawless fishes, save for lampreys and
hagfish, as well as the Placodermi, a group of armoured fish that dominated much of
the late Silurian. The Devonian also saw the rise of the first labyrinthodonts, which was a transitional between fishes and amphibians. Mesozoic vertebrates The reptiles appeared from labyrinthodonts in the subsequent Carboniferous period. The anapsid and synapsid reptiles were common during the late Paleozoic, while the diapsids became dominant during the Mesozoic. In the sea, the bony fishes became dominant. The dinosaurs gave rise to the birds in the Jurassic.[20] The demise of the dinosaurs at the end of the Cretaceous promoted expansion of the mammals, which had evolved from the therapsids, a group of synapsid reptiles, during the late Triassic Period. After the dinosaurs The post-dinosaur world has seen great diversification of bony fishes, frogs, birds
and mammals. Over half of all living vertebrate species
(about 32,000 species) are fishes (non-
tetrapod craniates), a diverse set of
lineages that inhabit all the world's aquatic
ecosystems, from snow minnows
(Cypriniformes) in Himalayan lakes at elevations over 4,600 metres (15,000 feet)
to flatfishes (order Pleuronectiformes) in
the Challenger Deep, the deepest ocean
trench at about 11,000 metres (36,000
feet). Fishes of myriad varieties are the
main predators in most of the world’s water bodies, both freshwater and marine.
The rest of the vertebrate species are
tetrapods, a single lineage that includes
amphibians (frogs, with more than 5,800
species; salamanders, with about 580
species; and caecilians, with about 175 species); mammals (with over 5,400
species); and reptiles and birds (with more
than 18,000 species). Tetrapods dominate
the megafauna of most terrestrial
environments (including fossorial and
arboreal realms) and also include many partially or fully aquatic groups (e.g., sea snakes, penguins, cetaceans). Classification There are several ways of classifying
animals. Evolutionary systematics relies on anatomy, physiology and evolutionary history, which is determined through
similarities in anatomy and, if possible, the genetics of organisms. Phylogenetic classification is based solely on phylogeny. [21] Evolutionary systematics gives an overview; phylogenetic systematics gives
detail. The two systems are thus complementary rather than opposed.[22] Traditional classification Traditional spindle diagram of the evolution of the vertebrates at class level Conventional classification has living
vertebrates grouped into seven classes
based on traditional interpretations of
gross anatomical and physiological traits. This classification is the one most
commonly encountered in school
textbooks, overviews, non-specialist, and
popular works. The extant vertebrates are: [8]Subphylum Vertebrata Class Agnatha (jawless fishes) Class Chondrichthyes (cartilaginous fishes) Class Osteichthyes (bony fishes) Class Amphibia (amphibians) Class Reptilia (reptiles) Class Aves (birds) Class Mammalia (mammals) In addition to these comes two classes of
extinct armoured fishes, the Placodermi and the Acanthodii. Other ways of classifying the vertebrates have been
devised, particularly with emphasis on the phylogeny on early amphibians and reptiles. An example based on Janvier
(1981, 1997), Shu et al. (2003), and Benton (2004)[23] is given here: Subphylum Vertebrata Superclass Agnatha or Cephalaspidomorphi (lampreys and other jawless fishes) Infraphylum Gnathostomata (vertebrates with jaws) Class †Placodermi (extinct armoured fishes) Class Chondrichthyes (cartilaginous fishes) Class †Acanthodii (extinct spiny "sharks") Superclass Osteichthyes (bony fishes) Class Actinopterygii (ray-finned bony fishes) Class Sarcopterygii (lobe-finned fishes, some ancestral to
tetrapods) Superclass Tetrapoda (four-limbed vertebrates) Class Amphibia (amphibians, some ancestral to the amniotes) Class †Synapsida (extinct mammal-like "reptiles", some
ancestral to mammals,
sometimes classed with
Reptilia) Class Reptilia (reptiles, some ancestral to birds) Class Aves (birds) Class Mammalia (mammals) While this traditional classification is
orderly, most of the groups are paraphyletic, i.e. do not contain all descendants of the class's common ancestor.[23] For instance, descendants of the first reptiles include modern reptiles as
well as birds. Most of the classes listed are
not "complete" taxa, meaning that they do not include all the descendants of the first
representative of the group. For example,
the agnathans have given rise to the jawed vertebrates ; the bony fishes have given rise to the land vertebrates; the traditional "amphibians" have given rise to the reptiles (traditionally including the synapsids, or "mammal-like "reptiles"), which in turn have given rise to the
mammals and birds. Most scientists
working with vertebrates use a
classification based purely on phylogeny, organized by their known evolutionary
history and sometimes disregarding the
conventional interpretations of their
anatomy and physiology. Phylogenetic relationships In phylogenetic taxonomy, the relationships between animals are not
typically divided into ranks, but illustrated
as a nested "family tree" known as a cladogram. Phylogenetic groups are given definitions based on their relationship to
one another, rather than purely on physical
traits such as the presence of a backbone.
This nesting pattern is often combined
with traditional taxonomy (as above), in a
practice known as evolutionary taxonomy . The cladogram presented below is based
on studies compiled by Philippe Janvier
and others for the Tree of Life Web Project. [24] Vertebrata Hyperoartia (lampreys) ?†Euconodonta unnamed †Pteraspidomorphi ?†Thelodonti unnamed ?†Anaspida unnamed †Galeaspida unnamed ?†Pituriaspida †Osteostraci Gnathostomata †Placodermi (armoured fishes) unnamed Chondrichthyes (cartilaginous fishes) Teleostomi †Acanthodii Osteichthyes Actinopterygii (ray-finned fishes) Sarcopterygii ?†Onychodontiformes Coelacanthimorpha (coelacanths) unnamed †Porolepiformes Dipnoi (lungfishes) unnamed †Rhizodontimorpha unnamed †Tristichopteridae Four limbed
vertebrates
OVARIES
The ovary is an ovum-producing reproductive organ, often found in pairs as
part of the vertebrate female reproductive system. Ovaries in anatomically female individuals are analogous to testes in anatomically male individuals, in that they
are both gonads and endocrine glands. Human anatomy Ovaries are oval shaped. The ovary (for a
given side) is located in the lateral wall of
the pelvis in a region called the ovarian fossa. The fossa usually lies beneath the external iliac artery and in front of the ureter and the internal iliac artery. The ovaries aren't attached to the fallopian tubes but to the outer layer of the uterus via the ovarian ligaments. Usually each
ovary takes turns releasing eggs every
month; however, if there was a case
where one ovary was absent or
dysfunctional then the other ovary would
continue providing eggs to be released. Hormones Ovaries secrete both estrogen and progesterone. Estrogen is responsible for the appearance of secondary sex characteristics of anatomically female people at puberty and for the maturation and maintenance of the reproductive
organs in their mature functional state.
Progesterone functions with estrogen by
promoting menstrual cycle cyclic changes in the endometrium. Ligaments In the human the paired ovaries lie within
the pelvic cavity, on either side of the
uterus, to which they are attached via a
fibrous cord called the ovarian ligament. The ovaries are uncovered in the peritoneal cavity but are tethered to the body wall via the suspensory ligament of the ovary. The part of the broad ligament of the uterus that covers the ovary is known as the mesovarium. Thus, the ovary is the only organ in the human body which
is totally invaginated into the peritonium,
making it the only interperitoneal organ
(not to be confused with intraperitoneal). Extremities There are two extremities to the ovary: The end to which the uterine tube attaches is called the tubal extremity. The other extremity is called the uterine
extremity. It points downward, and it is
attached to the uterus via the ovarian
ligament. Histology Cell types Follicular cells flat epithelial cells that originate from surface epithelium
covering the ovary granulosa cells - surrounding follicular
cells have changed from flat to cuboidal
and proliferated to produce a stratified
epithelium Gametes[1] Section of the ovary of a newly born child. Germinal epithelium is seen at top. Primitive ova are seen in their cell-nests. The Genital cord or genital ridge is still discernible in this young child. A blood vessel and an ovarian follicle is also seen The outermost layer is called the ovarian
surface epithelium (previously known
as the germinal epithelium). The tunica albuginea covers the cortex. The ovarian cortex consists of ovarian follicles and stroma in between them. Included in the follicles are the cumulus oophorus, membrana granulosa (and the granulosa cells inside it), corona radiata, zona pellucida, and primary oocyte . The zona pellucida, theca of follicle, antrum and liquor folliculi are also contained in the follicle. Also in the cortex is the corpus luteum derived from the follicles. The innermost layer is the ovarian medulla. It can be hard to distinguish between the cortex and medulla, but
follicles are usually not found in the
medulla. In other animals Ovaries of some kind are found in the
female reproductive system of many
animals that employ sexual reproduction, including invertebrates. However, they
develop in a very different way in most
invertebrates than they do in vertebrates, and are not truly homologous.[2] Many of the features found in human
ovaries are common to all vertebrates,
including the presence of follicular cells,
tunica albuginea, and so on. However,
many species produce a far greater number
of eggs during their lifetime than do humans, so that, in fish and amphibians,
there may be hundreds, or even millions of
fertile eggs present in the ovary at any
given time. In these species, fresh eggs
may be developing from the germinal
epithelium throughout life. Corpora lutea are found only in mammals, and in some elasmobranch fish; in other species, the remnants of the follicle are quickly
resorbed by the ovary. In birds, reptiles,
and monotremes, the egg is relatively large, filling the follicle, and distorting the shape of the ovary at maturity. [2] Amphibians and reptiles have no ovarian
medulla; the central part of the ovary is a
hollow, lymph-filled space. The ovary of teleosts is also often hollow, but in this case, the eggs are shed into the cavity, which opens into the oviduct.[2] Although most normal female vertebrates
have two ovaries, this is not the case in all
species. In birds and platypuses, the right ovary never matures, so that only the left
is functional. In some elasmobranchs, the
reverse is true, with only the right ovary
fully developing. In the primitive jawless fish, and some teleosts, there is only one ovary, formed by the fusion of the paired organs in the embryo.[2] Cryopreservation Cryopreservation of ovarian tissue, often called Ovarian Tissue Cryopreservation , is of interest to women who want to
preserve their reproductive function
beyond the natural limit, or whose
reproductive potential is threatened by cancer therapy,[3] for example in hematologic malignancies or breast cancer. [4] The procedure is to take a part of the ovary and carry out slow freezing before
storing it in liquid nitrogen whilst therapy
is undertaken. Tissue can then be thawed
and implanted near the fallopian, either
orthotopic (on the natural location) or heterotopic (on the abdominal wall),[4], where it starts to produce new eggs,
allowing normal conception to take place. [5] A study of 60 procedures concluded that ovarian tissue harvesting appears to be safe.[4] The ovarian tissue may also be transplanted into mice that are
immunocompromised (SCID mice) to avoid graft rejection, and tissue can be harvested later when mature follicles have developed.
CLITORIS
The clitoris is a complex structure, with
both external and internal components.
Projecting at the front of the labial commissure where the edges of the outer lips (labia majora) meet at the base of the pubic mound is the clitoral hood (prepuce), which in full or part covers the head
(clitoral glans). Following from the head back and up along the shaft, it is found that
this extends up to several centimeters
before reversing direction and branching.
The resulting branched shape forms an
inverted "V", extending as a pair of "legs"
known as the clitoral crura formed of the corpora cavernosa. The clitoral crura are concealed behind the labia minora, and terminate with attachment to the pubic arch (according to some),[5] or follow interior to the labia minora to meet at the fourchette (according to others).[2] Associated are the urethral sponge, clitoral/vestibular bulbs, perineal sponge, a network of nerves and blood vessels,
suspensory ligaments, muscles and pelvic diaphragm.[6] There is considerable variation in how
much of the clitoris protrudes from the
hood and how much is covered by it,
ranging from complete, covered invisibility
to full, protruding visibility. An article
published in the Journal of Obstetrics and Gynecology in July 1992 states that the
average width of the clitoral glans lies
within the range of 2.5 to 4.5 millimetres
(0.098 to 0.18 in), indicating that the
average size is smaller than a pencil-top eraser. Recent discoveries about the size of the clitoris show that clitoral tissue
extends some considerable distance inside
the body, around the vagina. It is now
clear that clitoral tissue is far more
widespread than the small visible part most people associate with the word. [3] There is no identified correlation between
the size of a clitoris and a woman's age,
height, weight, use of hormonal contraceptives, or being post-menopausal. Sexual stimulation Click here to see a video showing clitoris becoming engorged with blood Research shows most women achieve orgasm only through clitoral stimulation.[3] [7][8][9][10][11]Masters and Johnson were the first to determine that the clitoral
structures surround and extend along and
within the labia. They observed that both
clitoral and vaginal orgasms had the same stages of physical response, and argued
that clitoral stimulation is the primary source of both kinds of orgasms.[7] Supporting these findings is a 2005 study
which investigated the size of the clitoris;
Australian urologist Dr. Helen O'Connell, while using MRI technology, noted a direct relationship between the legs or roots of
the clitoris and the erectile tissue of the clitoral bulbs and corpora, and the distal urethra and vagina.[3] O'Connell asserts that this interconnected relationship is the
physiological explanation for the
conjectured G-Spot and experience of vaginal orgasm, taking into account the
stimulation of the internal parts of the clitoris during vaginal penetration.[3] "The vaginal wall is, in fact, the clitoris," said
O'Connell. "If you lift the skin off the
vagina on the side walls, you get the bulbs
of the clitoris – triangular, crescental
masses of erectile tissue." The idea was
that the clitoris is more than just its glans – the "little hill".[3] Pulled-out clitoris During sexual arousal and during orgasm, the clitoris and the whole of the genitalia
engorge and change color as these erectile
tissues fill with blood, and the individual
experiences vaginal contractions. Masters
and Johnson documented the sexual response cycle, which has four phases and is still the clinically accepted definition of
the human orgasm. More recent research
has determined that some can experience
a sustained intense orgasm through
stimulation of the clitoris and remain in the
orgasmic phase for much longer than the original studies indicated, evidenced by
genital engorgement, color changes, and vaginal contractions.[12] Embryonic development Stages in the development of clitoris During the development of an embryo , at the time of development of the urinary and reproductive organs, the previously undifferentiated genital tubercle develops into either a clitoris or penis, along with all
other major organ systems, making them homologous.[6] The clitoris is formed from the same tissues that would have become
the glans and upper shaft of a penis if the embryo had been exposed to “male” hormones. Changes in appearance of male
and female embryos begin roughly eight
weeks after conception. By birth, the
genital structures have developed into the female reproductive system .[13] Embryo sex based on external genitalia is
apparent to a doctor at the end of the 14th
menstrual week, and the sex can usually be
identified by an ultrasound after 16 to 18 menstrual weeks.[14] A condition that can develop from naturally occurring or
deliberate exposure to higher than average
levels of testosterone is clitoromegaly. Recognition of existence The clitoris has been thought of as
"discovered" and "rediscovered" through
empirical documentation by male scholars repeatedly over the centuries. [15] Over a period of more than 2,500 years, some
have considered the clitoris and the penis
equivalent in all respects except their arrangement.[2]Realdo Colombo (also known as Matteo Renaldo Colombo) was a
lecturer in surgery at the University of Padua, Italy, and in 1559 he published a book called De re anatomica[16] in which he described the "seat of woman's
delight". Disregarding females' awareness
of their own bodies, Colombo concluded,
"Since no one has discerned these
projections and their workings, if it is
permissible to give names to things discovered by me, it should be called the love or sweetness of Venus."[17] Colombo's claim was disputed by his
successor at Padua, Gabriele Falloppio (who discovered the fallopian tube), who claimed that he was the first to discover
the clitoris. Caspar Bartholin, a 17th- century Danish anatomist, dismissed both claims, arguing that the clitoris had been
widely known to medical science since the second century. Indeed, Hippocrates used the term columella (little pillar). Avicenna named the clitoris the albatra or virga
(rod). Albucasis, an Arabic medical authority, named it tentigo (tension). It
was also known to the Romans, who named it (vulgar slang) landica.[18] This cycle of suppression and discovery
continued, notably in the work of Regnier de Graaf (Tractatus de Virorum Organis Generationi Inservientibus, De Mulierum
Organis Generationi Inservientibus
Tractatus Novus) in the 17th century and Georg Ludwig Kobelt (Die männlichen und weiblichen Wollustorgane des Menschen
und einiger Säugetiere) in the 19th. De
Graaf criticised Columbo's claims for this.
(Harvey, Laqueur). The full extent of the clitoris was alluded to
by Masters and Johnson in 1966, but in such
a muddled fashion that the significance of
their description became obscured. In
1981, the Federation of Feminist Women's
Health Clinics (FFWHC) continued this process with anatomically precise illustrations.[2] Today, MRI complements these efforts, as it is both a live and multiplanar method of examination.[3] Female genital mutilation Main article: Female genital mutilation The clitoris may be partially or totally
removed during female genital mutilation
(FGM), also known as a clitoridectomy, or female circumcision. This is carried out in
several countries in Africa, and to a lesser
extent in the Middle East and Southeast
Asia, on girls from a few days old to the age of 15.[19]Amnesty International estimates that over two million FGM procedures are performed every year. [20] Female genital modification Main article: Genital modification and mutilation In various cultures, the clitoris is
sometimes pierced directly. In U.S. body modification culture, it is actually
extremely rare for the clitoral shaft itself to
be pierced, as of the already few people
who desire the piercing, only a small
percentage are anatomically suited for it;
furthermore, most piercing artists are reluctant to attempt such a delicate
procedure. Some styles, such as the Isabella, do pass through the clitoris but are placed deep at the base, where they
provide unique stimulation; they still
require the proper genital build, but are
more common than shaft piercings.
Additionally, what is (erroneously)
referred to as a "clit piercing" is almost always the much more common (and much
less complicated) clitoral hood piercing. Enlargement may be intentional or
unintentional. Those taking hormones and/
or other medications as part of female-to- male transition usually experience dramatic clitoral growth; individual desires
(and the difficulties of surgical
phalloplasty) often result in the retention
of the original genitalia, the enlarged
clitoris analogous to a penis as part of the
transition. However, the clitoris cannot reach the size of most cissexual men's penises through hormones. Surgery to add
function to the clitoris, such as metoidioplasty or clitoral release, are alternatives to phalloplasty (construction of a penis) which permit retention of
sexual sensation in the clitoris. On the other hand, use of anabolic steroids by bodybuilders and other athletes can
result in significant enlargement of the
clitoris in concert with other masculinizing
effects on their bodies. Temporary
engorgement results from suction
pumping, practiced to enhance sexual pleasure or for aesthetic purposes.
LABIA
The labia are anatomical structures that are part of the female genitalia; they are
the major externally visible portions of the vulva . In humans, there are two pairs of labia: the outer labia, or labia majora are larger and fattier, while the labia minora are folds of skin often concealed within the
outer labia. The labia surround and protect
the clitoris and the openings of the vagina and urethra.
SEX ORGAN
A sex organ, or primary sexual characteristic, as narrowly defined, is any of the anatomical parts of the body which
are involved in sexual reproduction and constitute the reproductive system in a complex organism; flowers are the reproductive organs of flowering plants, [1]cones are the reproductive organs of coniferous plants,[2] whereas mosses, ferns, and other similar plants have gametangia for reproductive organs.[3] Animals This section requires expansion. Mammals In mammals, sex organs include: Female Male Bartholin's glands cervix clitoris clitoral hood clitoral glans (glans clitoridis) Fallopian tubes labium ovaries Skene's gland uterus vagina vulva Human female external sex organ with pubic hair removed bulbourethral
glands epididymis penis foreskin glans penis prostate scrotum seminal vesicles testicles Human male external sex organs Development Main article: Development of the reproductive system In typical prenatal development, sexual organs originate from a common anlage anatomy during early gestation and differentiate into male or female
variations. The SRY gene, usually located on the Y chromosome and encoding the testis determining factor, determines the direction of this differentiation. The
absence of it allows the gonads to continue
to develop into ovaries. Thereafter, the development of the
internal reproductive organs and the external genitalia is determined by hormones produced by certain fetal gonads
(ovaries or testes) and the cells' response
to them. The initial appearance of the fetal genitalia (a few weeks after conception) looks basically feminine: a pair of
"urogenital folds" with a small protuberance in the middle, and the urethra behind the protuberance. If the fetus has testes, and if the testes produce
testosterone, and if the cells of the genitals
respond to the testosterone, the outer
urogenital folds swell and fuse in the
midline to produce the scrotum; the
protuberance grows larger and straighter to form the penis; the inner urogenital
swellings grow, wrap around the penis,
and fuse in the midline to form the penile
urethra. Each sexual organ in one sex has a homologous counterpart in the other one. See a list of homologues of the human reproductive system . In a larger perspective, the whole process
of sexual differentiation also includes development of secondary sexual characteristics such as patterns of pubic and facial hair and female breasts that
emerge at puberty. Furthermore,
differences in brain structure arise,
affecting, but not absolutely determining,
behavior. Plants This section requires expansion. Flowering plants Sexual reproduction in flowering plants involves the union of the male and female
germ cells. The sex organs, contained
within the flower, may contain both male
and female sex organs (these are known as
perfect, bisexual, or hermaphrodite) or only one of the two (known as imperfect or
unisexual). Also, those plants whose
flowers are unisexual may contain both
male and female flowers, or there may be
purely male and female plants of the same
species. During a plant's sexual reproduction the stamen (male sex organ) produces pollen from an anther. These male germ cells are
carried to the pistil (female sex organ), with the ovary at its base where fertilization can take place. The male germ cells can be carried by air, rain, water,
insects or other symbiotic animals, or simply by gravity. Terminology The Latin term genitalia, sometimes anglicized as genital area, is used to describe the externally visible sex organs, known as primary genitalia or external genitalia: in males, the penis and scrotum; and in females, the clitoris and vulva . The other, hidden sex organs are referred
to as the secondary genitalia or internal genitalia. The most important of these are the gonads, a pair of sex organs, specifically the testes in the male or the ovaries in the female. Gonads are the true sex organs, generating reproductive gametes containing inheritable DNA. They also produce most of the primary hormones
that affect sexual development, and
regulate other sexual organs and sexually
differentiated behaviors. A more ambiguously defined term is erogenous zone, subjectively, any portion of the body that when stimulated produces erotic sensation, but always prominently including the genitalia. Anatomical terms related to sex The following is a list of anatomical terms
related to sex and sexuality: Anterior fornix erogenous zone Areola Bartholin's gland Breast Bulbospongiosus muscle Bulbourethral gland Cervix Pudendal cleft Clitoris Corona of glans penis Corpus cavernosum of clitoris Corpus spongiosum penis Cremaster muscle Dartos Deep perineal pouch Egg (biology) Ejaculatory duct Endometrium Epididymis Fallopian tube Foreskin Frenulum Frenulum clitoridis Frenulum labiorum pudendi Frenulum of prepuce of penis Fundiform ligament G-spot Gartner's duct Genital tubercle Genitofemoral nerve Glans Hymen Internal pudendal artery Intromittent organ Ischiocavernosus muscle Labia majora Labia minora Labium (genitalia) Mammary gland meatus Mons pubis Müllerian duct Nipple Ovary Ovum Penile artery Penis Perineum Prepuce Prostate Pubic hair Pubic symphysis Pubococcygeus muscle Pudendal nerve Perineal raphe Recto-uterine pouch Ridged band Scrotum Seminal vesicle Seminiferous tubule Skene's gland Spermatic cord Spermatozoon Splanchnic nerves Testicle Tunica albuginea of testis Urethra Urethral sphincter Urethral sponge Uterus Vagina Vas deferens Vulva See also Castration Circumcision Erogenous zone Genital modification and mutilation Human sexuality Hysterectomy Intersexuality Intimate parts List of transgender-related topics Mastectomy Obstetrics and gynaecology Oophorectomy Secondary sex characteristics Sex Human sexual behavior Sexual intercourse List of sex positions
VAGINA
The vagina (from Latin vagĭna, literally "sheath" or "scabbard") is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the oviduct. The Latinate plural "vaginae" is rarely used in
English. The word vagina is quite often used
colloquially to refer to the vulva or female genitals generally; technically speaking,
the vagina is a specific internal structure.
In humans, the passage leads from the
opening of the vulva to the uterus (womb). It lies midway between the anal tract and the urethra.[1] Location and structure The human vagina is an elastic muscular canal that extends from the cervix to the vulva .[2] Although there is wide anatomical
variation, the length of the unaroused
vagina of a woman of child-bearing age is
approximately 6 to 7.5 cm (2.5 to 3 in)
across the anterior wall (front), and 9 cm
(3.5 in) long across the posterior wall (rear).[3] During sexual arousal the vagina expands in both length and width.[4] Its elasticity allows it to stretch during sexual intercourse and during birth to offspring.[5] The vagina connects the superficial vulva
to the cervix of the deep uterus. If the woman stands upright, the vaginal
tube points in an upward-backward
direction and forms an angle of slightly more than 45 degrees with the uterus. The
vaginal opening is at the caudal end of the vulva, behind the opening of the urethra. The upper one-fourth of the vagina is
separated from the rectum by the recto- uterine pouch. Above the vagina is the Mons pubis. The vagina, along with the inside of the vulva, is reddish pink in color,
as are most healthy internal mucous
membranes in mammals. A series of ridges
produced by folding of the wall of the
outer third of the vagina is called the
vaginal rugae. They are transverse epithelial ridges and their function is to provide the vagina with increased surface
area for extension and stretching. Vaginal lubrication is provided by the Bartholin's glands near the vaginal opening and the cervix. The membrane of the
vaginal wall also produces moisture,
although it does not contain any glands.
Before and during ovulation, the cervix's mucus glands secretes different variations
of mucus, which provides an alkaline environment in the vaginal canal that is
favorable to the survival of sperm. The hymen is a membrane of tissue which is situated at the opening of the vagina. As
in many female animals, the hymen covers
the opening of the vagina from birth until
it is ruptured during sexual or other
activity. The tissue may be ruptured by
vaginal penetration, delivery, a pelvic examination, injury, or sports. The absence of a hymen does not indicate prior sexual
activity, as it is not always ruptured during sexual intercourse.[6] Similarly, its presence does not indicate a lack of prior
sexual activity, as light activity may not
rupture it, and it can be surgically restored. Function The vagina has several biological functions. Sexual activity Further information: Human sexual activity The concentration of the nerve endings
that lie close to the entrance of a woman's
vagina can provide pleasurable sensation
during sexual activity, when stimulated in
a way that the particular woman enjoys.
During sexual arousal, and particularly the stimulation of the clitoris, the walls of the vagina self-lubricate. This reduces friction that can be caused by various sexual
activities. Research has found that portions
of the clitoris extend into the vulva and vagina.[7] With arousal, the vagina lengthens rapidly
to an average of about 4 in.(10 cm), but
can continue to lengthen in response to pressure.[8] As the woman becomes fully aroused, the vagina tents (last ²⁄₃)
expands in length and width, while the cervix retracts.[9] The walls of the vagina are composed of soft elastic folds of
mucous membrane which stretch or
contract (with support from pelvic muscles)
to the size of the inserted penis or other object, stimulating the penis and helping to
cause the male to experience orgasm and ejaculation, thus enabling fertilization. G-Spot Main article: G-Spot Structure of the wall of vagina An erogenous zone commonly referred to as the G-Spot (also known as the
Gräfenberg Spot) is located at the anterior
wall of the vagina, about five centimeters
in from the entrance. Some women
experience intense pleasure if the G-Spot is
stimulated appropriately during sexual activity. A G-Spot orgasm may be responsible for female ejaculation, leading some doctors and researchers to believe
that G-Spot pleasure comes from the Skene's glands, a female homologue of the prostate, rather than any particular spot on the vaginal wall. [10][11][12] Some researchers dispute the existence of the G- Spot.[13] Childbirth During childbirth, the vagina provides the channel to deliver the infant from the uterus to its independent life outside the body of the mother. During birth, the elasticity of the vagina allows it to stretch
to many times its normal diameter. The
vagina is often typically referred to as the
birth canal in the context of pregnancy and
childbirth, though the term is, by
definition, the area between the outside of the vagina and the fully dilated uterus. [14] Uterine secretions The vagina provides a path for menstrual blood and tissue to leave the body. In industrial societies, tampons, menstrual cups and sanitary napkins may be used to absorb or capture these fluids. Clinical relevance An ultrasound showing the urinary bladder (1), uterus (2), and vagina (3) Main article: Vulvovaginal health The vagina is self-cleansing and therefore
usually needs no special treatment. Doctors
generally discourage the practice of douching.[15] Since a healthy vagina is colonized by a mutually symbiotic flora of microorganisms that protect its host from
disease-causing microbes, any attempt to
upset this balance may cause many
undesirable outcomes, including but not
limited to abnormal discharge and yeast infection. The acidity of a healthy vagina of a woman of child-bearing age (a pH of around 4.5) is due to the degradation of glycogen to the lactic acid by enzymes secreted by the Döderlein's bacillus. This is
a normal commensal of the vagina. The acidity retards the growth of many strains of dangerous microbes.[16] The vagina is examined during gynecological exams, often using a speculum, which holds the vagina open for visual inspection of the cervix or taking of
samples (see pap smear). Vaginismus Main article: Vaginismus Vaginismus, not to be confused with Vaginitis, refers to an involuntary tightening of the vagina, due to a
conditioned reflex of the muscles in the
area. It can affect any form of vaginal
penetration, including sexual intercourse,
insertion of tampons, and the penetration
involved in gynecological examinations. Various psychological and physical
treatments are possible to help alleviate it. Signs of disease Vaginal diseases present with lumps,
discharge and sores. Lumps The presence of unusual lumps in the wall
or base of the vagina is always abnormal.
The most common of these is Bartholin's cyst.[17] The cyst, which can feel like a pea, is formed by a blockage in glands
which normally supply the opening of the
vagina. This condition is easily treated
with minor surgery or silver nitrate. Other
less common causes of small lumps or
vesicles are herpes simplex. They are usually multiple and very painful with a
clear fluid leaving a crust. They may be
associated with generalized swelling and
are very tender. Lumps associated with
cancer of the vaginal wall are very rare
and the average age of onset is seventy years.[18] The most common form is squamous cell carcinoma, then cancer of the glands or adenocarcinoma and finally, and even more rarely, melanoma. A speculum allows physicians to examine the vagina and cervix. Discharge The great majority of vaginal discharges
are normal or physiological and include
blood or menses (from the uterus), the
most common, and clear fluid either as a
result of sexual arousal or secretions from
the cervix. Other non infective causes include dermatitis, discharge from foreign bodies such as retained tampons or foreign
bodies inserted by curious female children
into their own vaginas. Non-sexually
transmitted discharges occur from bacterial vaginosis and thrush or candidiasis. The final group of discharges include the
sexually transmitted diseases gonorrhea, chlamydia and trichomoniasis. The discharge from thrush is slightly pungent
and white, that from trichomoniasis more
foul and greenish, and that from foreign
bodies resembling the discharge of
gonorrhea, greyish or yellow and purulent (like pus).[19] Sores All sores involve a breakdown in the walls
of the fine membrane of the vaginal wall.
The most common of these are abrasions
and small ulcers caused by trauma. While
these can be inflicted during rape most are
actually caused by excessive rubbing from clothing or improper insertion of a sanitary
tampon. The typical ulcer or sore caused by syphilis is painless with raised edges. These are often undetected because they
occur mostly inside the vagina. The sores of
herpes which occur with vesicles are
extremely tender and may cause such
swelling that passing urine is difficult. In
the developing world a group of parasitic diseases also cause vaginal ulceration such
as Leishmaniasis but these are rarely encountered in the west. HIV/AIDS can be contracted through the vagina during
intercourse but is not associated with any local vaginal or vulval disease. [20] All the above local vulvovaginal diseases are
easily treated. Often only shame prevents patients from presenting for treatment.
SMOOTH MUSCLE
Smooth muscle is an involuntary non- striated muscle. It is divided into two sub- groups; the single-unit (unitary) and multiunit smooth muscle. Within single-
unit smooth muscle tissues, the autonomic
nervous system innervates a single cell
within a sheet or bundle and the action
potential is propagated by gap junctions to
neighboring cells such that the whole bundle or sheet contracts as a syncytium (i.e., a multinucleate mass of cytoplasm
that is not separated into cells). Multiunit
smooth muscle tissues innervate individual
cells; as such, they allow for fine control
and gradual responses, much like motor
unit recruitment in skeletal muscle. Smooth muscle is found within the walls of blood vessels (such smooth muscle specifically being termed vascular smooth muscle) such as in the tunica media layer of large (aorta) and small arteries, arterioles and veins. Smooth muscle is also found in lymphatic vessels, the urinary bladder, uterus (termed uterine smooth muscle), male and female reproductive tracts, gastrointestinal tract, respiratory tract, arrector pili of skin, the ciliary muscle, and iris of the eye. The structure and function is basically the same in
smooth muscle cells in different organs, but
the inducing stimuli differ substantially, in
order to perform individual effects in the
body at individual times. In addition, the glomeruli of the kidneys contain smooth muscle-like cells called mesangial cells. Structure Most smooth muscle is of the single-unit
variety, that is, either the whole muscle
contracts or the whole muscle relaxes, but
there is multiunit smooth muscle in the
trachea, the large elastic arteries, and the
iris of the eye. Single unit smooth muscle, however, is most common and lines blood
vessels (except large elastic arteries), the
urinary tract, and the digestive tract. Smooth muscle is fundamentally different
from skeletal muscle and cardiac muscle in terms of structure, function, regulation of
contraction, and excitation-contraction
coupling. Smooth muscle fibers have a fusiform shape and, like striated muscle, can tense and relax. However, smooth muscle containing tissue tend to demonstrate
greater elasticity and function within a
larger length-tension curve than striated
muscle. This ability to stretch and still
maintain contractility is important in
organs like the intestines and urinary bladder. In the relaxed state, each cell is
spindle-shaped, 20-500 micrometers in
length. Molecular structure A substantial portion of the volume of the
cytoplasm of smooth muscle cells are taken up by the molecules myosin and actin,[1] which together have the capability to
contract, and, through a chain of tensile
structures, make the entire smooth muscle
tissue contract with them. Myosin Myosin is primarily of class II in smooth muscle.[2] Myosin II contains two heavy chains
which constitute the head and tail
domains. Each of these heavy chains
contains the N-terminal head domain, while the C-terminal tails take on a coiled-coil morphology, holding the two heavy chains together (imagine two
snakes wrapped around each other, such
as in a caduceus). Thus, myosin II has two heads. In smooth muscle, there is a single gene (MYH11[3]) that codes for the heavy chains myosin II, but there
are splice variants of this gene that result in four distinct isoforms.[2] Also, smooth muscle may contain MHC that is
not involved in contraction, and that can arise from multiple genes.[2] Myosin II also contains 4 light chains,
resulting in 2 per head, weighing 20 (MLC20) and 17 (MLC17) kDa.[2] These bind the heavy chains in the "neck"
region between the head and tail. The MLC20 is also known as the regulatory light chain and actively participates in muscle contraction.[2] Two MLC20 isoforms are found in smooth muscle, and they are encoded
by different genes, but only one
isoform participates in contractility. [2] The MLC17 is also known as the essential light chain.[2] Its exact function is unclear, but it's believed
that it contributes to the structural
stability of the myosin head along with MLC20.[2] Two variants of MLC 17 (MLC17a/b) exist as a result of alternate splicing at the MLC17 gene. [2] Different combinations of heavy and light
chains allow for up to hundreds of different
types of myosin structures, but it is
unlikely that more than a few such
combinations are actually used or
permitted within a specific smooth muscle bed.[2] In the uterus, a shift in myosin expression has been hypothesized to avail
for changes in the directions of uterine contractions that are seen during the menstrual cycle.[2] Actin The thin filaments that form part of the
contractile machinery are predominantly composed of α- and γ-actin.[2] Smooth muscle α-actin (alpha actin) is the
predominate isoform within smooth
muscle. There are also lots of actin (mainly
β-actin) that does not take part in
contraction, but that polymerizes just
below the plasma membrane in the presence of a contractile stimulant and
may thereby assist in mechanical tension. [2] Alpha actin is also expressed as distinct genetic isoforms such there is smooth
muscle, cardiac muscle and skeletal muscle
specific isoforms of alpha actin. (ref The
actin gene family: function follows
isoform.Perrin BJ, Ervasti JM.Cytoskeleton
(Hoboken). 2010 Oct;67(10):630-4. Review.) The ratio of actin to myosin is between 2:1[2] and 10:1[2] in smooth muscle, compared to ~6:1 in skeletal muscle and 4:1
in cardiac muscle. Other proteins of the contractile
apparatus Smooth muscle does not contain the
protein troponin; instead calmodulin (which takes on the regulatory role in
smooth muscle), caldesmon and calponin are significant proteins expressed within
smooth muscle. Tropomyosin is present in smooth muscle, spanning seven actin monomers
and is laid out end to end over the entire
length of the thin filaments. In striated muscle, tropomyosin serves to enhance actin–myosin interactions, but in
smooth muscle, its function is unknown. [2] Calponin molecules may exist in equal number as actin, and has been proposed to be a load-bearing protein.[2] Caldesmon has been suggested to be involved in tethering actin, myosin and
tropomyosin, and thereby enhance the
ability of smooth muscle to maintain tension.[2] Also, all three of these proteins may have a
role in inhibiting the ATPase activity of the
myosin complex that otherwise provides energy to fuel muscle contraction.[2] Other tensile structures The myosin and actin are the contractile
parts of continuous chains of tensile
structures that stretch both across and
between smooth muscle cells. The actin filaments of contractile units are
attached to dense bodies. Dense bodies are rich in α-actinin,[2] and also attach intermediate filaments (consisting largely
of vimentin and desmin), and thereby appear to serve as anchors from which the thin filaments can exert force.[2] Dense bodies also are associated with β-actin,
which is the type found in the
cytoskeleton, suggesting that dense bodies
may coordinate tensions from both the
contractile machinery and the cytoskeleton.[2] The intermediate filaments are connected
to other intermediate filaments via dense
bodies, which eventually are attached to adherens junctions (also called focal adhesions) in the cell membrane of the smooth muscle cell, called the sarcolemma. The adherens junctions consist of large
number of proteins including α-actinin, vinculin and cytoskeletal actin. [2] The adherens junctions are scattered around
dense bands that are circumfering the smooth muscle cell in a rib-like pattern.[1] The dense band (or dense plaques) areas
alternate with regions of membrane
containing numerous caveolae. When
complexes of actin and myosin contract,
force is transduced to the sarcolemma
through intermediate filaments attaching to such dense bands. During contraction, there is a spatial
reorganization of the contractile
machinery to optimize force development. [2] part of this reorganization consists of vimentin being phosphorylated at Ser56 by a p21 activated kinase, resulting in some disassembly of vimentin polymers. [2] Also, The number of myosin filaments is
dynamic between the relaxed and
contracted state in some tissues as the
ratio of actin to myosin changes, and the
length and number of myosin filaments
change. Smooth muscle cells have been observed
contracting in a spiral corkscrew fashion,
and contractile proteins have been
observed organizing into zones of actin
and myosin along the axis of the cell. Smooth muscle-containing tissue needs to
be stretched often, so elasticity is an
important attribute of smooth muscle.
Smooth muscle cells may secrete a complex
extracellular matrix containing collagen (predominantly types I and III), elastin, glycoproteins, and proteoglycans. Smooth muscle also has specific elastin and
collagen receptors to interact with these
proteins of the extracellular matrix. These
fibers with their extracellular matrices
contribute to the viscoelasticity of these tissues. For example, the great arteries are
viscolelastic vessels that act like a Windkessel, propagating ventricular contraction and smoothing out the pulsatile
flow, and the smooth muscle within the tunica media contributes to this property. Caveolae The sarcolemma also contains caveolae,
which are microdomains of lipid rafts
specialized to cell-signaling events and ion
channels. These invaginations in the
sarcoplasma contain a host of receptors (prostacyclin, endothelin, serotonin, muscarinic receptors, adrenergic
receptors), second messenger generators (adenylate cyclase , Phospholipase C), G proteins (RhoA, G alpha), kinases (rho kinase-ROCK, Protein kinase C, Protein Kinase A), ion channels (L type Calcium channels, ATP sensitive Potassium channels, Calcium sensitive Potassium channels) in close proximity. The caveolae are often close to sarcoplasmic reticulum or
mitochondria, and have been proposed to
organize signaling molecules in the
membrane. Excitation-contraction coupling A smooth muscle is excited by external
stimuli, which causes contraction. Each
step is further detailed below. Inducing stimuli and factors Smooth muscle may contract
spontaneously (via ionic channel dynamics)
or as in the gut special pacemakers cells interstitial cells of Cajal produce rhythmic contractions. Also, contraction, as well as
relaxation, can be induced by a number of
physiochemical agents (e.g., hormones,
drugs, neurotransmitters - particularly from
the autonomic nervous system . Smooth muscle in various regions of the
vascular tree, the airway and lungs,
kidneys and vagina is different in their
expression of ionic channels, hormone
receptors, cell-signaling pathways, and
other proteins that determine function. External substances For instance, most blood vessels respond to norepinephrine and epinephrine (from sympathetic stimulation or the adrenal medulla) by producing vasoconstriction
(this response is mediated through alpha 1- adrenergic receptors). Blood vessels in skeletal muscle and cardiac muscle respond
to these catecholamines producing vasodilation because the smooth muscle
possess beta-adrenergic receptors. Generally, arterial smooth muscle responds
to carbon dioxide by producing
vasodilation, and responds to oxygen by
producing vasoconstriction. Pulmonary
blood vessels within the lung are unique as
they vasodilate to high oxygen tension and vasoconstrict when it falls. Bronchiole,
smooth muscle that line the airways of the
lung, respond to high carbon dioxide
producing vasodilation and vasoconstrict
when carbon dioxide is low. These
responses to carbon dioxide and oxygen by pulmonary blood vessels and bronchiole
airway smooth muscle aid in matching
perfusion and ventilation within the lungs.
Further different smooth muscle tissues
display extremes of abundant to little
sarcoplasmic reticulum so excitation- contraction coupling varies with its
dependence on intracellular or extracellular
calcium. Stretch Recent research indicates that sphingosine-1-phosphate (S1P) signaling is an important regulator of vascular smooth muscle contraction. When transmural pressure increases, sphingosine kinase 1 phosphorylates sphingosine to S1P, which
binds to the S1P2 receptor in plasma
membrane of cells. This leads to a transient
increase in intracellular calcium, and
activates Rac and Rhoa signaling
pathways. Collectively, these serve to increase MLCK activity and decrease MLCP
activity, promoting muscle contraction.
This allows arterioles to increase
resistance in response to increased blood
pressure and thus maintain constant blood
flow. The Rhoa and Rac portion of the signaling pathway provides a calcium-
independent way to regulate resistance artery tone.[4] Spread of impulse To maintain organ dimensions against
force, cells are fastened to one another by adherens junctions. As a consequence, cells are mechanically coupled to one another
such that contraction of one cell invokes
some degree of contraction in an adjoining
cell. Gap junctions couple adjacent cells chemically and electrically, facilitating the
spread of chemicals (e.g., calcium) or action
potentials between smooth muscle cells.
Single unit smooth muscle displays
numerous gap junctions and these tissues
often organize into sheets or bundles which contract in bulk. Contraction Smooth muscle contraction is caused by the
ripping of myosin and actin filaments (a sliding filament mechanism) over each other. The energy for this to happen is
provided by the hydrolysis of ATP. Myosin functions as an ATPase utilizing ATP to
produce a molecular conformational
change of part of the myosin and produces
movement. Movement of the filaments
over each other happens when the globular
heads protruding from myosin filaments attach and interact with actin filaments to
form crossbridges. The myosin heads tilt
and drag along the actin filament a small
distance (10-12 nm). The heads then
release the actin filament and then
changes angle to relocate to another site on the actin filament a further distance
(10-12 nm) away. They can then re-bind to
the actin molecule and drag it along
further. This process is called crossbridge
cycling and is the same for all muscles (see muscle contraction). Unlike cardiac and skeletal muscle, smooth muscle does not
contain the calcium-binding protein
troponin. Contraction is initiated by a
calcium-regulated phosphorylation of
myosin, rather than a calcium-activated
troponin system. Crossbridge cycling causes contraction of
myosin and actin complexes, in turn
causing increased tension along the entire
chains of tensile structures, ultimately
resulting in contraction of the entire
smooth muscle tissue. Phasic or tonic Smooth muscle may contract phasically
with rapid contraction and relaxation, or
tonically with slow and sustained
contraction. The reproductive, digestive,
respiratory, and urinary tracts, skin, eye,
and vasculature all contain this tonic muscle type. This type of smooth muscle
can maintain force for prolonged time with
only little energy utilization. There are
differences in the myosin heavy and light
chains that also correlate with these
differences in contractile patterns and kinetics of contraction between tonic and
phasic smooth muscle. Activation of myosin heads Crossbridge cycling cannot occur until the
myosin heads have been activated to
allow crossbridges to form. When the light
chains are phosphorylated, they become
active and will allow contraction to occur.
The enzyme that phosphorylates the light chains is called myosin light-chain kinase (MLCK), also called MLC20 kinase.[2] In order to control contraction, MLCK will
work only when the muscle is stimulated
to contract. Stimulation will increase the
intracellular concentration of calcium ions.
These bind to a molecule called calmodulin, and form a calcium-calmodulin complex. It
is this complex that will bind to MLCK to
activate it, allowing the chain of reactions
for contraction to occur. Activation consists of phosphorylation of a serine on position 19 (Ser19) on the MLC20 light chain, which causes a conformational
change that increases the angle in the neck domain of the myosin heavy chain, [2] which corresponds to the part of the cross-
bridge cycle where the myosin head is
unattached to the actin filament and
relocates to another site on it. After
attachment of the myosin head to the actin
filament, this serine phosphorylation also activates the ATPase activity of the myosin
head region to provide the energy to fuel the subsequent contraction.[2] Phosphorylation of a threonine on position
18 (Thr18) on MLC20 is also possible and
may further increase the ATPase activity of the myosin complex.[2] Sustained maintenance Phosphorylation of the MLC20 myosin light chains correlates well with the shortening
velocity of smooth muscle. During this
period there is a rapid burst of energy
utilization as measured by oxygen
consumption. Within a few minutes of
initiation the calcium level markedly decrease, MLC20 myosin light chains phosphorylation decreases, and energy
utilization decreases and the muscle can
relax. Still, smooth muscle has the ability of
sustained maintenance of force in this
situation as well. This sustained phase has
been attributed to certain myosin crossbridges, termed latch-bridges, that are
cycling very slowly, notably at the cycle
stage where dephosphorylated myosin
complexes detach from the actin, thereby
maintaining the force at low energy costs. [2] This phenomenon is of great value especially for tonically active smooth muscle.[2] Isolated preparations of vascular and
visceral smooth muscle contract with
depolarizing high potassium balanced
saline generating a certain amount of
contractile force. The same preparation
stimulated in normal balanced saline with an agonist such as endothelin or serotonin
will generate more contractile force. This
increase in force is termed calcium
sensitization. The myosin light chain
phosphatase is inhibited to increase the
gain or sensitivity of myosin light chain kinase to calcium. There are number of cell
signalling pathways believed to regulate
this decrease in myosin light chain
phosphatase: a RhoA-Rock kinase
pathway, a Protein kinase C-Protein kinase
C potentiation inhibitor protein 17 (CPI-17) pathway, telokin, and a Zip kinase
pathway. Further Rock kinase and Zip
kinase have been implicated to directly
phosphorylate the 20kd myosin light
chains. Other contractile mechanisms Other cell signaling pathways and protein
kinases (Protein kinase C, Rho kinase, Zip kinase, Focal adhesion kinases) have been
implicated as well and actin
polymerization dynamics plays a role in
force maintenance. While myosin light
chain phosphorylation correlates well with
shortening velocity, other cell signaling pathways have been implicated in the
development of force and maintenance of
force. Notably the phosphorylation of
specific tyrosine residues on the focal
adhesion adapter protein-paxillin by
specific tyrosine kinases has been demonstrated to be essential to force
development and maintenance. For
example, cyclic nucleotides can relax
arterial smooth muscle without reductions
in crossbridge phosphorylation, a process
termed force suppression. This process is mediated by the phosphorylation of the
small heat shock protein, hsp20, and may prevent phosphorylated myosin heads
from interacting with actin. Relaxation The phosphorylation of the light chains by
MLCK is countered by a myosin light-chain phosphatase, which dephosphorylates the MLC20 myosin light chains and thereby inhibits contraction.[2] Other signaling pathways have also been implicated in the
regulation actin and myosin dynamics. In
general, the relaxation of smooth muscle is
by cell-signaling pathways that increase
the myosin phosphatase activity, decrease
the intracellular calcium levels, hyperpolarize the smooth muscle, and/or
regulate actin and myosin dynamics. Relaxation-inducing factors The relaxation of smooth muscle can be
mediated by the endothelium-derived
relaxing factor-nitric oxide, endothelial
derived hyperpolarizing factor (either an
endogenous cannabinoid, cytochrome P450
metabolite, or hydrogen peroxide), or prostacyclin (PGI2). Nitric oxide and PGI2
stimulate soluble guanylate cyclase and
membrane bound adenylate cyclase,
respectively. The cyclic nucleotides (cGMP
and cAMP) produced by these cyclases
activate Protein Kinase G and Proten Kinase A and phosphorylate a number of
proteins. The phosphorylation events lead
to a decrease in intracelluar calcium
(inhibit L type Calcium channels, inhibits
IP3 receptor channels, stimulates
sarcoplasmic reticulum Calcium pump ATPase), a decrease in the 20kd myosin
light chain phosphorylation by altering
calcium sensitization and increasing
myosin light chain phosphatase activity, a
stimulation of calcium sensitive potassium
channels which hyperpolarize the cell, and the phosphorylation of amino acid residue
serine 16 on the small heat shock protein
(hsp20)by Protein Kinases A and G. The
phosphorylation of hsp20 appears to alter
actin and focal adhesion dynamics and
actin-myosin interaction, and recent evidence indicates that hsp20 binding to
14-3-3 protein is involved in this process.
An alternative hypothesis is that
phosphorylated Hsp20 may also alter the
affinity of phosphorylated myosin with
actin and inhibit contractility by interfering with crossbridge formation. The
endothelium derived hyperpolarizing
factor stimulates calcium sensitive
potassium channels and/or ATP sensitive
potassium channels and stimulate
potassium efflux which hyperpolarizes the cell and produces relaxation. Invertebrate smooth muscle In invertebrate smooth muscle, contraction
is initiated with the binding of calcium
directly to myosin and then rapidly cycling
cross-bridges, generating force. Similar to
the mechanism of vertebrate smooth
muscle, there is a low calcium and low energy utilization catch phase. This
sustained phase or catch phase has been
attributed to a catch protein that has
similarities to myosin light-chain kinase
and the elastic protein-titin called twitchin.
Clams and other bivalve mollusks use this catch phase of smooth muscle to keep their
shell closed for prolonged periods with
little energy usage. Specific effects Although the structure and function is
basically the same in smooth muscle cells
in different organs, their specific effects or
end-functions differ. Smooth muscle forms precapillary
sphincters in blood vessels in metarterioles
which regulates the blood flow in capillary
beds of various organs and tissues. The
contractile function of vascular smooth
muscle also regulates the lumenal diameter of the small arteries-arterioles called
resistance vessels, thereby contributing
significantly to setting the level of blood
pressure. Smooth muscle contracts slowly
and may maintain the contraction
(tonically) for prolonged periods in blood vessels, bronchioles, and some sphincters.
Activating arteriole smooth muscle can
decrease the lumenal diameter 1/3 of
resting so it drastically alters blood flow
and resistance. Activation of aortic smooth
muscle doesn't significantly alter the lumenal diameter but serves to increase
the viscoelasticity of the vascular wall. In the digestive tract, smooth muscle
contracts in a rhythmic peristaltic fashion, rhythmically forcing foodstuffs through the
digestive tract as the result of phasic
contraction. A non-contractile function is seen in
specialized smooth muscle within the
afferent arteriole of the juxtaglomerular
apparatus, which secretes renin in response to osmotic and pressure changes,
and also it is believed to secrete ATP in
tubuloglomerular regulation of glomerular
filtration rate. Renin in turn activates the renin-angiotensin system to regulate blood pressure. Growth and rearrangement The mechanism in which external factors
stimulate growth and rearrangement is not
yet fully understood. A number of growth
factors and neurohumoral agents influence
smooth muscle growth and differentiation.
The Notch receptor and cell-signaling pathway have been demonstrated to be
essential to vasculogenesis and the
formation of arteries and veins. The embryological origin of smooth muscle
is usually of mesodermal origin. However,
the smooth muscle within the Aorta and
Pulmonary arteries (the Great Arteries of
the heart) is derived from
ectomesenchyme of neural crest origin, although coronary artery smooth muscle is
of mesodermal origin. Related diseases "Smooth muscle condition" is a condition in
which the body of a developing embryo
does not create enough smooth muscle for
the gastrointestinal system. This condition is fatal. Anti-smooth muscle antibodies (ASMA) can be a symptom of an auto-immune disorder, such as hepatitis, cirrhosis, or lupus. Vascular smooth muscle tumors are very
rare. They can be malignant or benign, and
morbidity can be significant with either
type. Intravascular leiomyomatosis is a
benign neoplasm that extends through the
veins; angioleiomyoma is a benign neoplasm of the extremities; vascular
leiomyosarcomas is a malign neoplasm
that can be found in the inferior vena cava,
pulmonary arteries and veins, and other
peripheral vessels. See Atherosclerosis.
MIF
Anti-Müllerian hormone also known as AMH is a protein that, in humans, is encoded by the AMH gene.[1] It inhibits the development of the Müllerian ducts (paramesonephric ducts) in the male embryo.[2] It has also been called Müllerian inhibiting factor (MIF), Müllerian- inhibiting hormone (MIH), and Müllerian- inhibiting substance (MIS). It is named after Johannes Peter Müller. Species distribution AMH is present in fish, reptiles, birds, marsupials, and placental mammals. Source AMH is secreted by Sertoli cells of the testes during embryogenesis of the fetal male. Structure AMH is a protein hormone structurally related to inhibin and activin, and a member of the transforming growth factor-β (TGF-β) family. It is a dimeric glycoprotein. Gene In humans, the gene for AMH is AMH, on chromosome 19p13.3,[1] while the gene AMHR2 codes for its receptor on chromosome 12.[3] Function Embryogenesis In mammals, AMH prevents the
development of the mullerian ducts into the uterus and other mullerian structures. [2] The effect is ipsilateral, that is each testis suppresses Müllerian development only on its own side. [4] In humans, this action takes place during the first 8 weeks
of gestation. If no hormone is produced
from the gonads, the Mullerian ducts
automatically develop, while the Wolffian
ducts, which are responsible for male reproductive ducts, automatically die. [5] Amounts of AMH that are measurable in
the blood vary by age and sex. AMH works
by interacting with specific receptors on the surfaces of the cells of target tissues.
The best-known and most specific effect,
mediated through the AMH type II
receptors, includes programmed cell death
(apoptosis) of the target tissue (the fetal mullerian ducts). Ovarian Model of AMH in healthy females from conception to the menopause, based on measurements taken from 3,260 individuals In healthy females AMH is either just
detectable or undetectable in cord blood at
birth and demonstrates a marked rise by
three months of age; while still detectable
it falls until four years of age before rising
linearly until eight years of age remaining fairly constant from mid-childhood to early
adulthood - it does not change significantly
during puberty; from 25 years of age AMH declines to undetectable levels at menopause.[6] AMH is expressed by granulosa cells of the ovary during the reproductive years, and controls the
formation of primary follicles by inhibiting
excessive follicular recruitment by FSH. It, therefore, has a role in folliculogenesis,[7] and some authorities suggest it is a
measure of certain aspects of ovarian function[8], useful in assessing conditions such as polycystic ovary syndrome and premature ovarian failure.[9] Other AMH production by the Sertoli cells of the testes remains high throughout childhood
in males but declines to low levels during
puberty and adult life. AMH has been
shown to regulate production of sex hormones,[10] and changing AMH levels (falling in females, rising in males) may be
involved in the onset of puberty in both
sexes. Functional AMH receptors have also
been found to be expressed on neurons in
the brains of embryonic mice, and are
thought to play a role in sexually dimorphic brain development and consequent
development of gender-specific behaviours.[11] Pathology In men, inadequate embryonal AMH
activity can lead to the Persistent Müllerian duct syndrome (PMDS), in which a rudimentary uterus is present and testes
are usually undescended. The AMH gene (AMH) or the gene (AMH-RII) for its
receptor are usually abnormal. AMH
measurements have also become widely
used in the evaluation of testicular
presence and function in infants with intersex conditions, ambiguous genitalia, and cryptorchidism. Application Normative model of AMH in healthy females, showing ranges into which 68% and 95% of the healthy population are expected to fall. Values relate to the IBC assay for serum AMH AMH has been synthesized. Its ability to
inhibit growth of tissue derived from the
Müllerian ducts has raised hopes of
usefulness in the treatment of a variety of
medical conditions including endometriosis, adenomyosis, and uterine cancer. Research is underway in several laboratories. Comparison of an individual's AMH level with respect to average levels [12] is also useful in fertility assessment, as it provides
a guide to ovarian reserve and identifies women that may need to consider either
egg freezing or trying for a pregnancy
sooner rather than later if their long-term future fertility is poor. [13] Measuring AMH alone may be misleading as high levels
occur in conditions like polycystic ovarian syndrome and therefore AMH levels should be considered in conjunction with a transvaginal scan of the ovaries to assess antral follicle count[14] and ovarian volume [15]. It also has the potential to rationalise the
programme of ovulation induction and
decisions about the number of embryos to
transfer in assisted reproduction
techniques to maximise pregnancy success
rates whilst minimising the risk of ovarian hyperstimulation syndrome (OHSS) [16][17] AMH can predict an excessive response in ovarian hyperstimulation with a sensitivity and specificity of 82% and 76%, respectively.
MULLERIAN DUCTS
Müllerian ducts (or paramesonephric ducts) are paired ducts of the embryo that run down the lateral sides of the urogenital ridge and terminate at the Müllerian eminence in the primitive urogenital sinus. In the female, they will develop to form
the Fallopian tubes, uterus, cervix, and the upper third of the vagina;[1] in the male, they are lost. These ducts are made of tissue of mesodermal origin.[2] Development Müllerian duct (blue) develops in females (middle image) and degenerates in males (bottom). The female reproductive system is
composed of two embryological segments:
the urogenital sinus and the Müllerian
ducts. The two are conjoined at the Müllerian tubercle.[3] Müllerian ducts are present on the embryo of both sexes.[4] Only in females do they develop into
reproductive organs. They degenerate in
males, but the adjoining Wolffian ducts develop into male reproductive organs. The
sex based differences in the contributions
of the Müllerian ducts to reproductive
organs is based on the presence, and
degree of presence, of Müllerian Inhibiting factor. Regulation of development The development of the Müllerian ducts is
controlled by the presence or absence of
"AMH", or Anti-Müllerian hormone (also known as "MIF" for "Müllerian-inhibiting
factor", or "MIH" for "Müllerian-inhibiting hormone").[5] Male
embryogenesis The testes produce AMH
and as a
result the
development
of the
Müllerian ducts is
inhibited. Disturbances
can lead to persistent
Müllerian duct
syndrome. The ducts
disappear
except for
the
vestigial vagina
masculina and the appendix
testis. Female
embryogenesis The absence
of AMH
results in the
development
of female
reproductive organs, as
noted above. Disturbance in
the
development
may result in
uterine
absence (Müllerian agenesis) or uterine
malformations. The ducts
develop
into the
upper vagina, cervix, uterus and oviducts. Eponym They are named after Johannes Peter Müller, a physiologist who described these ducts in his text "Bildungsgeschichte der
Genitalien" in 1830.
OVARIAN ARTERY
In human anatomy, the ovarian artery is a blood vessel that supplies oxygenated blood to the ovary. It arises from the abdominal aorta below the renal artery, and does not pass out of the abdominal cavity. It can be found in the suspensory ligament of the ovary , anterior to the ovarian vein and ureter.[1] Relationship to internal spermatic It only exists in females. The ovarian arteries are the corresponding arteries in
the female to the testicular artery in the male. They are shorter than the internal spermatics. The origin and course of the first part of
each artery are the same as those of the
internal spermatic, but on arriving at the
upper opening of the lesser pelvis the ovarian artery passes inward, between the
two layers of the ovariopelvic ligament
and of the broad ligament of the uterus, to be distributed to the ovary. Branches Small branches are given to the ureter and the uterine tube, and one passes on to the side of the uterus, and unites with the uterine artery. Other offsets are continued on the round ligament of the uterus, through the inguinal canal, to the integument of the labium majus and groin. It commonly anastomoses (connects with) the uterine artery.
UTERINE ARTERY
The uterine artery is an artery that supplies blood to the uterus in females. Structure The uterine artery usually arises from the
anterior division of the internal iliac artery. It travels to the uterus, crossing the ureter anteriorly, reaching the uterus by traveling
in the cardinal ligament. It travels through the parametrium of the inferior broad ligament of the uterus. It commonly anastomoses (connects with) the ovarian artery. The uterine artery is the major blood
supply to the uterus and enlarges
significantly during pregnancy. Branches and organs supplied round ligament of the uterus ovary ("Ovarian branches") uterus (arcuate vessels) vagina ("Vaginal branches" - azygos arteries of the vagina) uterine tube ("Tubal branch")
RETROVERTED UTERUS
A retroverted uterus (tilted uterus, tipped uterus) is a uterus that is tilted backwards instead of forwards. This is in contrast to
the slightly "anteverted" uterus that most women have, which is tipped forward
toward the bladder, with the anterior end slightly concave. Between 1 in 3 and 1-in-5 women
(depending on the source) has a
retroverted uterus, which is tipped
backwards towards the spine. Related terms The following table distinguishes among
some of the terms used for the position of
the uterus: A retroverted uterus should be
distinguished from the following: Distinction More common Less common Position
tipped "anteverted":
tipped
forward "retroverted":
tipped
backwards Position of
fundus "anteflexed":
the fundus is
pointing
forward
relative to the
cervix. Anterior of
uterus is
concave. "retroflexed":
the fundus is
pointing
backwards.
Anterior of
uterus is convex. Additional terms include: retrocessed uterus: both the superior
and inferior ends of the uterus are
pushed posteriorly severely anteflexed uterus: the uterus is
in the same position as "normal" and
bends in the same direction (concave is
anterior) but the bend is much
pronounced vertical uterus: the fundus (top of the uterus) is straight up. Causes In most cases, a retroverted uterus is
genetic and is perfectly normal but there
are other factors that can cause the uterus to be retroverted.[1] Some cases are caused by pelvic surgery, pelvic adhesions, endometriosis, fibroids, pelvic inflammatory disease, or the labor of childbirth. Diagnosis A retroverted uterus is usually diagnosed
during a routine pelvic examination.[citation needed] It can cause pain in the lower back.[citation needed] It usually does not pose any medical
problems, though it can be associated with dyspareunia (pain during sexual intercourse) and dysmenorrhea (pain during menstruation).[citation needed] Fertility & Pregnancy Uterine position has no effect on fertility.[citation needed] A tipped uterus will usually right itself during the 10th to
12th week of pregnancy. If a uterus does not right itself, it may be
labeled persistent. Treatment Treatment options are rarely needed, and
include exercises, a pessary, manual repositioning, and surgery.
LINEA TERMINALIS
The linea terminalis or innominate line consists of the pectineal line, the arcuate line, and the sacral promontory.[1] It is part of the pelvic brim, which is the edge of the pelvic inlet. The pelvic inlet is typically used to divide the abdominopelvic cavity into an abdominal (above the inlet) and a pelvic cavity (below the inlet). Sometimes, the pelvis
cavity is considered to extend above the
pelvic inlet, and in this case the pelvic inlet
is used to divide the pelvic cavity into a false (above the inlet) and a true pelvis (below the inlet).
FRONTAL PLANE
A coronal plane (also known as the frontal plane) is any vertical plane that divides the body into ventral and dorsal (belly and back) sections. It is one of the planes of the body used to describe the location of body parts in
relation to each other. Examples For a human, the mid-coronal plane would
transect a standing body into two halves
(front and back, or anterior and posterior)
in an imaginary line that cuts through both
shoulders. Terminology The term is derived from Latin corona
(“‘garland, crown’”), from Ancient Greek
κορώνη (korōnē), “‘garland, wreath’”). Larger perspective The coronal plane is an example of a longitudinal plane, because it is perpendicular to the transverse plane.
PUBIC SYMPHYSIS
The pubic symphysis or symphysis pubis is the midline cartilaginous joint (secondary cartilaginous) uniting the superior rami of the left and right pubic bones. It is located anterior to the urinary bladder and superior to the external genitalia; for females it is above the vulva and for males it is above the penis. In males, the suspensory ligament of the penis attaches to the pubic symphysis. In females, the pubic symphysis is intimately
close to the clitoris. In normal adults it can be moved roughly 2 mm and with 1 degree
rotation. This increases for women at the time of child birth.[1] Anatomy Symphysis pubis is a nonsynovial amphiarthrodial joint, and comes from the Greek word "symphysis", meaning
growing together. The anterior width of
the symphysis pubis is 3-5 mm greater
than its intrapelvic posterior width. This
joint is connected by fibrocartilage and may contain a fluid filled cavity; the center
is avascular, possibly due to the nature of the compressive forces passing through
this joint, which may lead to harmful vascular disease.[2] The ends of both pubic bones are covered by a thin layer of hyaline cartilage attached to the fibrocartilage. The fibrocartilaginous disk is
reinforced by a series of ligaments. These
ligaments cling to the fibrocartilaginous
disk to the point that fibers intermix with
it. Two such ligaments are the superior and inferior, these being the ligaments that provide the most stability; the posterior
and anterior ligaments are weaker. The
strong and thicker superior ligament is
reinforced by the tendons of the rectus abdominis, obliques externus, gracilis and thigh adductors muscles. The inferior ligament in the pubic arch is known as the
arcuate pubic ligament. Fibrocartilage Fibrocartilage is composed of small chained bundles of thick, clearly defined, type I collagenfibers. This fibrous connective tissue bundles have cartilage cells between
them; these cells to a certain extent
resemble tendon cells. The collagenous
fibers are usually placed in an orderly
arrangement parallel to tension on the
tissue. It has a low content of glycosaminoglycans (2% of dry weight). Glycosaminoglycans are long, unbranched polysaccharides (relatively complex carbohydrates) consisting of repeating disaccharide units. Fibrocartilage does not have a surrounding perichondrium. Perichondrium surrounds the cartilage of
developing bone; it has a layer of dense
irregular connective tissue and functions in
the growth and repair of cartilage. Hyaline cartilage Hyaline cartilage is the white, shiny gristle at the end of long bones. This cartilage has
very poor healing potential, and efforts to
induce it to repair itself frequently end up
with a similar, but poorer fibrocartilage. Physiology Analysis of the pelvis shows the skinny
regions function as arches, transferring the
weight of the upright trunk from the
sacrum to the hips. The symphysis pubis
connects these two weight-bearing arches,
and the ligaments that surround this pelvic region maintain the mechanical integrity. The main motions of the symphysis pubis
are superior/inferior glide and separation/
compression. The functions of the joint are
to absorb shock during walking and allow
delivery of a baby. Development In the newborn, the symphysis pubis is
9-10 mm in width, with thick cartilaginous
end-plates. By mid-adolescence the adult
size is achieved. During adulthood the end-
plates decrease in width to a thinner layer.
Degeneration of the symphysis pubis accompanies aging and postpartum. Women have a greater thickness of this
pubic disc which allows more mobility of
the pelvic bones, hence providing a greater
diameter of pelvic cavity during childbirth. Pregnancy During pregnancy in the human, hormones
such as relaxin remodel this ligamentous capsule allowing the pelvic bones to be
more flexible for delivery. The non-
pregnant gap of the symphysis pubis is
4-5 mm but in pregnancy there will be an
increase of at least 2-3 mm, therefore, it is
considered that a total width of up to 9 mm between the two bones is normal for a
pregnant woman. The symphysis pubis
separates to some degree during the
birthing process. In some women this
separation can become a diastasis of the symphysis pubis . The diastasis could be the result of a rapid birth[3] or a forceps delivery[4] or maybe even be prenatal.[5] A diastasis of the symphysis pubis is a
symptom of pelvic girdle pain (PGP). Overall, about 45% of all pregnant women
and 25% of all women postpartum suffer from PGP.[6] Symphysiotomy Before the Caesarean section technique was available, if labor failed to progress
because the head of the fetus was too
large, the mother's symphysis pubis was
cut and the skull of the fetus was crushed.
The Caesarean section has allowed the largely safe delivery of such infants. [7] In remote, isolated areas, women
presenting with a large baby and a small
pelvis must travel great distances for
medical help; a symphysiotomy has been suggested.[8] This practice was carried out in Europe before the introduction of the
Caesarean section. Diseases of the symphysis pubis Metabolic disease, such as renal osteodystrophy, produces widening, while ochronosis results in calcific deposits in the symphysis. Inflammatory disease, such as ankylosing spondylitis , results in bony fusion of the symphysis. Osteitis pubis, the most common inflammatory disease in this
area, is treated with anti-inflammatory
medication and rest. Degenerative joint
disease of the symphysis, which can cause
groin pain, results from instability or from abnormal pelvic mechanics.[9] Injury The pubic symphysis widens slightly
whenever the legs are stretched far apart.
In sports where these movements are
often performed, the risk of a pubic
symphysis blockage is high, in which case,
after completion of the movement, the bones at the symphysis do not realign
correctly and can get jammed in a dislocated position. The resulting pain can be quite severe, especially on further strain
put upon the affected joint. In most cases,
the joint can only be successfully reduced
into its normal position by a trained
medical professional. Use in forensic anthropology Pubic symphyses have importance in the
field of forensic anthropology, as they can
be used to estimate the age of adult
skeletons. Throughout life, the surfaces are
worn at a more or less predictable rate. By
examining the wear of the pubic symphysis, it is possible to estimate the age of the person at death.
ISCHIAL SPINE
From the posterior border of the body of
the Ischium there extends backward a thin and pointed triangular eminence, the ischial spine, more or less elongated in different subjects. It can serve as a landmark in pudendal anesthesia.[1] Surfaces external
surface gives attachment to the Gemellus superior internal
surface gives attachment to the Coccygeus, Levator ani, and the pelvic fascia pointed
extremity the sacrospinous ligament is attached.
SACRUM
In vertebrate anatomy the sacrum (plural: sacrums or sacra) is a large, triangular bone at the base of the spine and at the upper and back part of the pelvic cavity , where it is inserted like a wedge between the two hip bones. Its upper part connects with the last lumbar vertebra, and bottom part with the coccyx (tailbone). It consists of usually five initially unfused vertebrae which
begin to fuse between ages 16–18 and are
usually completely fused into a single bone
by age 26. It is curved upon itself and placed obliquely
(that is, tilted forward). It is kyphotic — that is, concave facing forwards. The base projects forward as the sacral promontory internally, and articulates with the last
lumbar vertebra to form the prominent sacrovertebral angle. The central part is curved outward towards the posterior, allowing greater room for the pelvic cavity. Etymology The name is derived from the Latin (os) sacrum, (sacer, sacra, sacrum, "sacred"), a translation of the Greek hieron (osteon), meaning sacred or strong bone.[1] Since the sacrum is the seat of the organs of
procreation, animal sacrums were offered
in sacrifices. In Slavic languages and in German this bone is called the "cross bone". [2] Parts The pelvic surface of the sacrum is concave from above downward, and
slightly so from side to side. The dorsal surface of the sacrum is convex and narrower than the pelvic. The lateral surface of the sacrum is broad above, but narrowed into a thin
edge below. The base of the sacrum, which is broad and expanded, is directed upward and
forward. The apex (apex oss. sacri) is directed
downward, and presents an oval facet
for articulation with the coccyx. The vertebral canal (canalis sacralis; sacral canal) runs throughout the greater
part of the bone; above, it is triangular
in form; below, its posterior wall is
incomplete, from the non-development
of the laminae and spinous processes. It
lodges the sacral nerves, and its walls are perforated by the anterior and
posterior sacral foramina through which
these nerves pass out. Articulations The sacrum articulates with four bones: the last lumbar vertebra above the coccyx (tailbone) below the illium portion of the hip bone on either side Rotation of the sacrum forward a few
degrees vis-à-vis the ilia is sometimes called "nutation" (L. "nodding"), and the reverse motion "counter-nutation."[3] It is called the sacrum when referred to all
of the parts combined, but sacral vertebrae
when referred individually. Sexual dimorphism The sacrum is noticeably sexually dimorphic (differently-shaped in males and females). In the female the sacrum is shorter and
wider than in the male; the lower half
forms a greater angle with the upper; the
upper half is nearly straight, the lower half
presenting the greatest amount of
curvature. The bone is also directed more obliquely backward; this increases the size
of the pelvic cavity and renders the
sacrovertebral angle more prominent. In the male the curvature is more evenly
distributed over the whole length of the
bone, and is altogether more massive than
in the female. Variations In some cases the sacrum will consist of six
pieces [1] or be reduced in number to four [2]. The bodies of the first and second vertebrae may fail to unite. Sometimes the uppermost transverse
tubercles are not joined to the rest of the
ala on one or both sides, or the sacral canal
may be open throughout a considerable
part of its length, in consequence of the
imperfect development of the laminae and spinous processes. The sacrum also varies considerably with
respect to its degree of curvature.
PUBOCERVICAL LIGAMENTS
The pubocervical ligament is a ligament connecting the side of the cervix to the pubic symphysis . The collagen in the pubocervical ligament
may be reduced in women with vaginal prolapse.
LIGAMENT
In anatomy, the term ligament is used to denote any of three types of structures. [1] Most commonly, it refers to fibrous tissue that connects bones to other bones and is also known as articular ligament, articular larua,[2]fibrous ligament, or true ligament. Ligament can also refer to: Peritoneal ligament: a fold of peritoneum or other membranes. Fetal remnant ligament: the remnants of
a tubular structure from the fetal period of life. The study of ligaments is known as desmology (from Greek δεσμός, desmos, "string"; and -λογία, -logia). Articular ligaments "Ligament" most commonly refers to a
band of tough, fibrous dense regular connective tissue comprising attenuated collagenous fibers. Ligaments connect bones to other bones to form a joint . They do not connect muscles to bones; that is the job oftendons. Some ligaments limit the mobility of articulations, or prevent certain
movements altogether. Capsular ligaments are part of the articular
capsule that surrounds synovial joints . They act as mechanical reinforcements. Extra-
capsular ligaments join together and
provide joint stability. Intra-capsular
ligaments, which are much less common,[citation needed] also provide stability but permit a far larger range of
motion. Cruciate ligaments occur in pairs. Ligaments are viscoelastic. They gradually lengthen when under tension, and return
to their original shape when the tension is
removed. However, they cannot retain
their original shape when stretched past a
certain point or for a prolonged period of
time. This is one reason why dislocated joints must be set as quickly as possible: if
the ligaments lengthen too much, then the
joint will be weakened, becoming prone to future dislocations.[citation needed] Athletes, gymnasts, dancers, and martial
artists perform stretching exercises to
lengthen their ligaments, making their
joints more supple. The term "double-jointed" refers to people
with more-elastic ligaments, allowing
their joints to stretch and contort further.
The medical term for describing such
double-jointed persons is hyperlaxity. The consequence of a broken ligament can
be instability of the joint. Not all broken
ligaments need surgery, but, if surgery is
needed to stabilise the joint, the broken
ligament can be repaired. Scar tissue may prevent this. If it is not possible to fix the
broken ligament, other procedures such as
the Brunelli procedure can correct the instability. Instability of a joint can over
time lead to wear of the cartilage and
eventually to osteoarthritis. Examples Head and neck Cricothyroid
ligament Periodontal
ligament Suspensory
ligament of the
lens Thorax Suspensory
ligament of the
breast Pelvis Anterior
sacroiliac
ligament Posterior
sacroiliac
ligament Sacrotuberous
ligament Sacrospinous
ligament Inferior pubic
ligament Superior pubic
ligament Suspensory
ligament of the
penis Wrist Palmar
radiocarpal
ligament Dorsal radiocarpal
ligament Ulnar collateral
ligament Radial collateral
ligament Knee Anterior cruciate
ligament (ACL) Lateral collateral
ligament (LCL) Posterior cruciate
ligament (PCL) Medial collateral
ligament (MCL) Cranial cruciate
ligament (CrCL) - quadruped equivalent of ACL Caudal cruciate
ligament (CaCL) - quadruped equivalent of PCL Patellar ligament Peritoneal ligaments Certain folds of peritoneum are referred to as ligaments. Examples include: The hepatoduodenal ligament, that surrounds the hepatic portal vein and other vessels as they travel from the duodenum to the liver. The broad ligament of the uterus, also a fold of peritoneum. Fetal remnant ligaments Certain tubular structures from the fetal
period are referred to as ligaments after
they close up and turn into cord-like structures:[citation needed] Fetal Adult ductus arteriosus ligamentum
arteriosum extra-hepatic portion of the fetal
left umbilical vein ligamentum teres
hepatis (the "round ligament of the
liver"). intra-hepatic
portion of the fetal
left umbilical vein
(the ductus venosus) ligamentum
venosum distal portions of the fetal left and right umbilical arteries medial umbilical
ligaments
PERITONEUM
The peritoneum is the serous membrane that forms the lining of the abdominal cavity or the coelom — it covers most of the intra-abdominal (or coelomic) organs
— in higher vertebrates and some invertebrates (annelids, for instance). It is composed of a layer of mesothelium supported by a thin layer of connective tissue. The peritoneum both supports the abdominal organs and serves as a conduit for their blood and lymph vessels and nerves. Structure Layers The abdominal cavity (the space bounded
by the vertebrae, abdominal muscles,
diaphragm and pelvic floor) should not be
confused with the intraperitoneal space
(located within the abdominal cavity, but
wrapped in peritoneum). For example, a kidney is inside the abdominal cavity, but
is retroperitoneal. Although they ultimately form one
continuous sheet, two types or layers of
peritoneum and a potential space between
them are referenced: The outer layer, called the parietal peritoneum, is attached to the abdominal wall. The inner layer, the visceral peritoneum, is wrapped around the internal organs that are located inside
the intraperitoneal cavity. The potential space between these two
layers is the peritoneal cavity; it is filled with a small amount (about 50 ml) of slippery serous fluid that allows the two layers to slide freely over each other. The term mesentery is often used to refer to a double layer of visceral
peritoneum. There are often blood
vessels, nerves, and other structures
between these layers. The space
between these two layers is technically
outside of the peritoneal sac, and thus not in the peritoneal cavity. Subdivisions There are two main regions of the
peritoneum, connected by the epiploic foramen (also known as the Omental Foramen or Foramen of Winslow): the greater sac (or general cavity of the abdomen), represented in red in the
diagrams above. the lesser sac (or omental bursa), represented in blue. The lesser sac is
divided into two "omenta": The lesser omentum (or gastrohepatic) is attached to the lesser curvature of the stomach and the liver. The greater omentum (or gastrocolic) hangs from the greater curve of the stomach and loops down in front of the intestines before curving back upwards to attach to the transverse colon. In effect it is draped in front of the intestines like an apron and may
serve as an insulating or protective
layer. The mesentery is the part of the peritoneum through which most abdominal
organs are attached to the abdominal wall and supplied with blood and lymph vessels and nerves. Structures include: SOURCES STRUCTURE FROM TO CONTAINS OMENTA dorsal
mesentery * greater omentum greater
curvature
of stomach (and spleen) transverse
colon dorsal
mesentery ** gastrosplenic ligament stomach spleen short gastric
artery, left gastro-
omental
artery dorsal
mesentery ** gastrophrenic
ligament stomach diaphragm left inferior
phrenic
artery dorsal
mesentery ** gastrocolic ligament stomach transverse
colon right gastro-
omental
artery - dorsal
mesentery ** splenorenal ligament spleen kidney splenic
artery, tail of pancreas ventral
mesentery * lesser omentum lesser
curvature
of the stomach (and duodenum) Liver the right free
margin-
hepatic
artery,portal
vein,and bile
duct. Along the lessar
curvature of
the stomach-
left and right
gastric artery. ventral
mesentery ** hepatogastric
ligament stomach liver right & left
gastric artery ventral
mesentery ** hepatoduodenal
ligament duodenum liver hepatic
artery proper, hepatic portal
vein, bile duct MESENTERIES dorsal
mesentery * Mesentery
proper small
intestine – jejunum and ileum posterior abdominal
wall superior
mesenteric
artery dorsal
mesentery * transverse mesocolon transverse
colon posterior abdominal
wall middle colic dorsal
mesentery * sigmoid mesocolon sigmoid
colon pelvic wall sigmoid
arteries dorsal
mesentery * mesoappendix mesentery
of ileum appendix appendicular
artery OTHER LIGAMENTS AND FOLDS ventral
mesentery * falciform ligament liver thoracic
diaphragm, anterior abdominal
wall round
ligament of
liver, paraumbilical
veins left umbilical
vein * round ligament of
liver liver umbilicus ventral
mesentery * coronary ligament liver thoracic
diaphragm ductus
venosus * ligamentum venosum liver liver * phrenicocolic ligament left colic
flexure thoracic
diaphragm ventral
mesentery * left triangular ligament, right triangular
ligament liver * umbilical folds urinary
bladder * ileocecal fold ileum cecum * broad ligament of the
uterus uterus pelvic wall mesovarium, mesosalpinx, mesometrium * ovarian ligament uterus inguinal
canal * suspensory ligament of the
ovary ovary pelvic wall ovarian
artery In addition, in the pelvic cavity there are several structures that are usually named
not for the peritoneum, but for the areas
defined by the peritoneal folds: Name Location Genders possessing structure Rectovesical
pouch between rectum and urinary
bladder male only Rectouterine
pouch between rectum and uterus female only Vesicouterine
pouch between urinary
bladder and uterus female only Pararectal
fossa surrounding rectum male and
female Paravesical
fossa surrounding urinary
bladder male and
female Development The peritoneum develops ultimately from
the mesoderm of the trilaminar embryo. As the mesoderm differentiates, one region
known as the lateral plate mesoderm splits to form two layers separated by an intraembryonic coelom. These two layers develop later into the visceral and parietal
layers found in all serous cavities, including the peritoneum. As an embryo develops, the various abdominal organs grow into the abdominal
cavity from structures in the abdominal
wall. In this process they become
enveloped in a layer of peritoneum. The
growing organs "take their blood vessels
with them" from the abdominal wall, and these blood vessels become covered by
peritoneum, forming a mesentery. Clinical aspects Peritoneal dialysis In one form of dialysis, called peritoneal dialysis, a glucose solution is sent through a tube into the peritoneal cavity. The fluid
is left there for a prescribed amount of
time to absorb waste products, and then
removed through the tube. The reason for
this effect is the high number of arteries
and veins in the peritoneal cavity. Through the mechanism of diffusion, waste products are removed from the blood. Classification of abdominal structures The structures in the abdomen are
classified as intraperitoneal, retroperitoneal or infraperitoneal depending on whether they are covered
with visceral peritoneum and whether
they are attached by mesenteries
(mensentery, mesocolon). Intraperitoneal Retroperitoneal Infraperitoneal / Subperitoneal Stomach, First part of the
duodenum
[5 cm], jejunum, ileum, cecum, appendix, transverse
colon, sigmoid colon, Rectum (upper 1/3) The rest of the duodenum, ascending colon, descending
colon, Rectum (middle 1/3) Rectum (lower 1/3) Liver, Spleen, Pancreas (full) Kidneys, adrenal glands, proximal
ureters, renal vessels Urinary bladder, distal ureters In women: Uterus, Fallopian tubes, ovaries Gonadal blood
vessels Inferior vena
cava, Aorta Structures that are intraperitoneal are
generally mobile, while those that are
retroperitoneal are relatively fixed in their
location. Some structures, such as the kidneys, are
"primarily retroperitoneal", while others
such as the majority of the duodenum, are
"secondarily retroperitoneal", meaning
that structure developed intraperitoneally
but lost its mesentery and thus became retroperitoneal. Etymology Peritoneum is derived from Greek via
Latin. Peri- means around, while -ton-
refers to stretching. Thus, peritoneum
means stretched around or stretched over.
UROGENITAL DIAPHRAGM
Older texts have asserted the existence of
an urogenital diaphragm, also called the triangular ligament, which was described as a layer of the pelvis that separates the deep perineal sac from the upper pelvis, lying between the inferior fascia of the urogenital diaphragm (perineal membrane) and superior fascia of the urogenital diaphragm. While this term is used to refer to a layer
of the pelvis that separates the deep perineal sac from the upper pelvis, such a discrete border of the sac probably does not exist.[1][2][3][4][5] While it has no official entry in Terminologia Anatomica, the term is still used occasionally to describe the muscular
components of the deep perineal pouch.
The urethra and the vagina, though part of
the pouch, are usually said to be passing
through the urogenital diaphragm, rather than part of the diaphragm itself. [2] Some researchers still assert that such a diaphragm exists, [6] and the term is still used in the literature.[7] The term "urogenital diaphragm" is often
confused with the pelvic floor, which is a true diaphragm supporting many of the
pelvic organs.
PERINEAL BODY
The perineal body (or central tendon of perineum) is a pyramidal fibromuscular mass in the middle line of the perineum at the junction between the urogenital
triangle and the anal triangle . It is found in
both males and females. In males, it is
found between the bulb of penis and the anus; in females, is found between the vagina and anus, and about 1.25 cm in front of the latter. The perineal body is essential for the
integrity of the pelvic floor, particularly in
females. Its rupture during delivery leads
to widening of the gap between the
anterior free borders of levator ani muscle
of both sides, thus predisposing the woman to prolapse of the uterus, rectum, or even the urinary bladder. Attachments At this point, the following muscles
converge and are attached: External anal sphincter muscle Bulbospongiosus muscle Superficial transverse perineal muscle Anterior fibers of the levator ani fibers from external urinary sphincter Deep transverse perineal muscle
PELVIC DIAPHRAGM
The pelvic floor or pelvic diaphragm is composed of muscle fibers of the levator ani, the coccygeus, and associated connective tissue which span the area underneath the pelvis. The pelvic diaphragm is a muscular partition formed
by the levatores ani and coccygei, with
which may be included the parietal pelvic
fascia on their upper and lower aspects.
The pelvic floor separates the pelvic cavity above from the perineal region (including perineum) below. The right and left levator ani lie almost
horizontally in the floor of the pelvis,
separated by a narrow gap that transmits
the urethra, vagina, and anal canal. The
levator ani is usually considered in three
parts: pubococcygeus, puborectalis, and iliococcygeus. The pubococcygeus, the main part of the levator, runs backward from the
body of the pubis toward the coccyx and
may be damaged during parturition. Some
fibers are inserted into the prostate,
urethra, and vagina. The right and left
puborectalis unite behind the anorectal junction to form a muscular sling. Some
regard them as a part of the sphincter ani externus. The iliococcygeus, the most posterior part of the levator ani, is often
poorly developed. The coccygeus, situated behind the levator
ani and frequently tendinous as much as
muscular, extends from the ischial spine to
the lateral margin of the sacrum and
coccyx. The pelvic cavity of the true pelvis has the pelvic floor as its inferior border (and the pelvic brim as its superior border). The perineum has the pelvic floor as its superior border. Some sources do not consider "pelvic floor"
and "pelvic diaphragm" to be identical,
with the "diaphragm" consisting of only
the levator ani and coccygeus, while the
"floor" also includes the perineal membrane and deep perineal pouch.[2] However, other sources include the fascia as part of the diaphragm.[3] In practice, the two terms are often used interchangeably. Posteriorly, the pelvic floor extends into
the anal triangle. Function It is important in providing support for
pelvic viscera (organs), e.g. the bladder, intestines, the uterus (in females), and in maintenance of continence as part of the urinary and anal sphincters. It facilitates birth by resisting the descent of the
presenting part, causing the fetus to rotate
forwards to navigate through the pelvic
girdle. Clinical significance In women, the levator muscles or their
supplying nerves can be damaged in
pregnancy or childbirth. There is some evidence that these muscles may also be
damaged during a hysterectomy. Pelvic surgery using the "perineal
approach" (between the anus and coccyx)
is an established cause of damage to the
pelvic floor. This surgery includes coccygectomy. In female high-level athletes, perineal
trauma is rare and is associated with
certain sports (each with a distinct type of
trauma): water-skiing, bicycle racing, and equestrian sports.[4] Damage to the pelvic floor not only
contributes to urinary incontinence but can
lead to pelvic organ prolapse. Pelvic organ prolapse occurs in women when pelvic
organs (e.g. the vagina, bladder, rectum, or
uterus) protrude into or outside of the
vagina. The causes of pelvic organ prolapse
are not unlike those that also contribute to
urinary incontinence. These include inappropriate (asymmetrical, excessive,
insufficient) muscle tone and asymmetries
caused by trauma to the pelvis. Age,
pregnancy, family history, and hormonal
status all contribute to the development of
pelvic organ prolapse. The vagina is suspended by attachments to the
perineum, pelvic side wall and sacrum via
attachments that include collagen, elastin,
and smooth muscle. Surgery can be
performed to repair pelvic floor muscles.
The pelvic floor muscles can be strengthened with Kegel exercises. Disorders of the posterior pelvic floor
include rectal prolapse, rectocele, perineal hernia, and a number of functional disorders including anismus. Constipation due to any of these disorders is called
"functional constipation" and is
identifiable by clinical diagnostic criteria. [5] Pelvic floor exercise (PFE), also known as Kegel exercises, may improve the tone and function of the pelvic floor muscles, which
is of particular benefit for women (and less
commonly men) who experience stress urinary incontinence.[6][7] However, compliance with PFE programs often is poor,[6] PFE generally is ineffective for urinary incontinence unless performed
with biofeedback and trained supervision, [7] and in severe cases it may have no benefit. Pelvic floor muscle tone may be
estimated using a perineometer, which measures the pressure within the vagina.
Medication may also be used to improve
continence. In severe cases, surgery may
be used to repair or even to reconstruct the
pelvic floor. Perineology or pelviperineology is a speciality dealing with the functional
troubles of the three axis (urological,
gynaecological and coloproctological) of
the pelvic floor.
PERIMETRIUM
The perimetrium (or serous coat of uterus) is the outer serosa layer of the uterus, equivalent to peritoneum.
PARAMETRIUM
In women, the supravaginal portion of the cervix is separated in front from the bladder by fibrous tissue, the parametrium (called cervical stroma in some texts),
which extends also on to its sides and
laterally between the layers of the broad ligaments. The uterine artery and ovarian ligament are located in the parametrium. Inflammation causes Parametritis.
mYOMETRIUM
The myometrium is the middle layer of the uterine wall, consisting mainly of uterine smooth muscle cells (also called uterine myocytes[1]), but also of supporting stromal and vascular tissue. Its main
function is to induce uterine contractions. Macrostructure The myometrium is located between the endometrium (the inner layer of the uterine wall), and the serosa or perimetrium (the outer uterine layer). The inner one-third of the myometrium
(termed the junctional or sub-endometrial
layer) appears to be derived from the Müllerian duct, while the outer, more predominant layer myometrium appears to
originate from non-Mullerian tissue, and is
the major contractile tissue during parturition and abortion.[1] Also, the junctional layer appears to function like a
circular muscle layer, capable of peristaltic and anti-peristaltic activity, equivalent to the muscular layer of the intestines.[1] Molecular muscular structure Further information: Smooth muscle The smooth muscle of the myometrium is basically very similar in molecular structure
to smooth muscle in other sites of the
body, with myosin and actin being the predominant proteins expressed.[1] In uterine smooth muscle, there is
approximately 6-fold more actin than myosin.[1] A shift in the myosin expression of the uterine smooth muscle has been
hypothesized to avail for changes in the
directions of uterine contractions that are seen during the menstrual cycle.[1] Contractile patterns Uterine smooth muscle has a phasic
pattern, shifting between a contractile
pattern and maintenance of a resting tone
with discrete, intermittent contractions of
varying frequency, amplitude and duration. [1] Also, as noted for the macrostructure of
uterine smooth muscle, the junctional layer
appears be capable of both peristaltic and anti-peristaltic activity. [1] Resting state The resting membrane potential (Vrest) of uterine smooth muscle has been recorded to be between -35 and -80 mV.[1] As with the resting membrane potential of other
cell types, it is basically maintained by a Na+/K+ pump that causes a higher concentration of Na+ ions in the extracellular space than in the intracellular space, and a higher concentration of K+ ions in the intracellular space than in the
extracellular space. Subsequently, having K + channels open to a higher degree than Na + channels results in an overall efflux of positive ions, resulting in a negative
potential. This resting potential undergoes rhythmic
oscillations, which have been termed slow
waves, and reflect intrinsic activity of slow wave potentials .[1] These slow waves are caused by changes in the distribution of Ca2+, Na+, K+ and Cl- ions between the intracellular and extracellular spaces,
which, in turn, reflects the permeability of
the plasma membrane to each of those ions.[1] K+ is the major ion responsible for such changes in ion flux, reflecting changes in various K+ channels.[1] Excitation-contraction This section requires expansion. The excitation-contraction coupling of uterine smooth muscle is also basically
very similar to smooth muscle in general, with intracellular increase in calcium (Ca2+) leading to contraction. However, the stimulating factors for uterine smooth
muscle differs from other types of smooth
muscle, availing for separate coordination
of uterine smooth muscle. Restoration to resting state This section requires expansion. Removal of Ca2+ after contraction induces relaxation of the smooth muscle, and
restores the molecular structure of the sarcoplasmic reticulum to avail for the next contractile stimulus.[1] Functions Further information: Uterine contraction The myometrium stretches (the smooth
muscle cells expand in both size and number[2]) during pregnancy to allow for the harboring of the pregnancy, and
contracts in a coordinated fashion, via a
positive feedback effect on the " Ferguson reflex"), during the process of labor. After delivery the myometrium contracts to expel the placenta and reduce blood loss. Thus a positive benefit to early breast
feeding is a natural stimulation of this
reflex to reduce blood loss and facilitate a
swift return to prepregnancy uterine and
abdominal muscle tone. Pathology Lack of contraction at this stage is termed uterine atony. After pregnancy the uterus returns to its nonpregnant size by a process
of myometrial involution. Neoplasms of the myometrium are very common, termed uterine leiomyomata or fibroids. Their malignant version, leiomyosarcoma, is rare.
FUNDUS
The fundus of the uterus is the top portion, opposite from the cervix. Fundal height, measured from the top of the pubic bone, is routinely measured in pregnancy to determine growth rates. If the measurement is smaller or larger than
what would be expected for gestational
age, it can be a crude indicator of an
abnormality (for example, a breech or sideways presentation, twins, or a placental issue), requiring further tests such as ultrasound to determine the exact nature of the problem, if any.
CAVITY OF THE BODY IN THE UTERUS
The Cavity of the Body in the uterus is a mere slit, flattened antero-posteriorly. It is triangular in shape, the base being
formed by the internal surface of the fundus between the orifices of the uterine tubes, the apex by the internal orifice of the uterus through which the cavity of the body communicates with the canal of the cervix.
CANAL OF THE CERVIX
In the anatomy of the female reproductive system, the canal of the cervix (also called the endocervical canal, cervical canal, cervical canal of uterus, or the cavity of cervix) is the spindle-shaped, flattened canal of the cervix, the neck of the uterus. It communicates with the uterine cavity via the internal orifice of the uterus, and with the vagina via the external orifice. The wall of the canal presents an anterior
and a posterior longitudinal ridge, from
each of which proceed a number of small
oblique columns, the palmate folds, giving
the appearance of branches from the stem
of a tree; to this arrangement the name arbor vitæ uteri is applied. The folds on the two walls are not exactly
opposed, but fit between one another so as
to close the cervical canal. Pathology Micrograph of an adenocarcinoma that arose from the endocervical mucosa. Pap stain. The endocervical mucosa is a site from
which adenocarcinoma can arise. Endocervical adenocarcinoma, like cervical
cancer (squamous cell carcinoma), often
arises in the milieu of human papilloma virus infection.[1] As most endometrial cancers are adenocarcinomas, differentiation of
endocervical adenocarcinoma and
endometrial adenocarcinomas is required,
as the treatment differs. Immunohistochemical staining is often helpful in this regard, endocervical
adenocarcinomas are typically CEA and p16 positive and estrogen receptor, progesterone receptor and vimentin negative.
EXTERNAL OS
The external orifice of the uterus (or ostium of uterus, or external os) is a small, depressed, somewhat circular aperture on
the rounded extremity of the vaginal portion of the cervix. Through this aperture, the cervical cavity communicates with that of the vagina. The external orifice is bounded by two lips,
an anterior and a posterior. The anterior is
shorter and thicker, though it projects
lower than the posterior because of the
slope of the cervix. Normally, both lips are
in contact with the posterior vaginal wall. In the prepartum condition, or prior to
pregnancy, the external orifice has a
rounded shape when viewed through the
vaginal canal (as through a speculum). Following parturition, the orifice takes on
an appearance more like a transverse slit
or is "H-shaped".
INTERNAL OS
The internal orifice of the uterus (or internal orifice of the cervix uteri or internal os) is an interior narrowing of the uterine cavity. It corresponds to a slight constriction known as the isthmus that can
be observed on the surface of the uterus about midway between the apex and
base.
DORSAL
For portion of the brain sometimes called
the dorsal, see Medial longitudinal fasciculus. In anatomy, the dorsum is the upper side of animals that typically run, fly, or swim
in a horizontal position, and the back side
of animals (like humans) that walk upright.
In vertebrates the dorsum contains the backbone. The term dorsal refers to anatomical structures that are either
situated toward or grow off that side of an
animal. The opposite side of the animal is
described with the terms ventrum and ventral. In lepidoptera (moths and butterflies), the dorsum also refers to the trailing edge of the wing (the leading edge is called the costa). Human neuroanatomy In the forebrain region in humans the term "dorsal" is used equivalently to
"superior" (towards the top of the head). [1] Nerve rootlets stemming from the spinal cord form dorsal (sensory) and ventral (motor) roots before these unite to form
the spinal nerve.
BICORNUATE UTERUS
A bicornuate uterus or bicornate uterus, commonly referred to as a "heart-shaped"
uterus, is a type of uterine malformation where two "horns" form at the upper part
of the uterus. Pathophysiology A bicornuate uterus is formed during embryogenesis. The fusion process of the upper part of the Müllerian ducts (Paramesonephric ducts) is altered. As a result the caudal part of the uterus is
normal while the cephalo part is
bifurcated. Classification There are many degrees of a bicornuate
uterus. There is a continuous range of the
degree and location of the Müllerian ducts (Paramesonephric ducts) fusion and existence of a spectrum rather than a fixed
number of types corresponding to strict
medical definitions. Two processes that
occur during the embryonic development
of the Müllerian ducts - fusion and
reabsorption - can be affected to different degrees.[1] The degree can determine the likeliness of a pregnancy reaching full-
term. Epidemiology The occurrence of all types of Müllerian duct
abnormalities in women is estimated around 0.4%.[2] A bicornuate uterus is estimated to occur in 0.1-0.5% of women
in the U.S. It is possible that this is an
underestimate since subtle abnormalities
often go undetected. Effect on reproduction Pregnancies in a bicornuate uterus are
usually considered high-risk and require
extra monitoring because of association
with poor reproduction potential. A bicornuate uterus is associated with
increased adverse reproductive outcomes
like: Recurrent pregnancy loss: the reproductive potential of a bicornuate
uterus is usually measured by live birth
rate (also called fetal survival rate). This
rate is estimated around 63% for a bicornuate uterus.[3] Preterm birth: with a 15 to 25% rate of preterm delivery. The reason that a
pregnancy may not reach full-term in a
bicornuate uterus often happens when
the baby begins to grow in either of the
protrusions at the top. A short cervical
length seems to be a good predicter of preterm delivery in women with a bicornuate uterus.[4] Malpresentation (breech birth or transverse presentation): a breech
presentation occurs in 40-50%
pregnancies with a partial bicornuate
uterus and not at all (0%) in a complete bicornuate uterus.[5] Previously, a bicornuate uterus was thought to be associated with infertility, [6] but recent studies have not confirmed such an association.[7] Diagnosis It is possible to diagnose a bicornuate uterus using gynecologic sonography, [8] specifically sonohysterography, and MRI.[9] However, as there is no indication to do
such procedures on asymptomatic women,
the presence of a bicornuate uterus may
not be detected until during pregnancy or
delivery. In a C-section (usually done due
to malpresentation) the irregular shape of the uterus can be noticed. Other less reliable imaging methods
include hysterosalpingography and hysteroscopy; these procedures are typically done during the course of an
infertility investigation.
THE ENDOMETRIUM
The endometrium is the inner membrane of the mammalian uterus. Function The endometrium functions as a lining for
the uterus, preventing adhesions between
the opposed walls of the myometrium, thereby maintaining the patency of the
uterine cavity. During the menstrual cycle or estrous cycle, the endometrium grows to a thick, blood vessel-rich, glandular tissue
layer. This represents an optimal
environment for the implantation of a blastocyst upon its arrival in the uterus. The endometrium is central, echogenic
(detectable using ultrasound scanners), and
has an average thickness of 6.7mm. During pregnancy, the glands and blood vessels in the endometrium further increase in size and number. Vascular
spaces fuse and become interconnected,
forming the placenta, which supplies oxygen and nutrition to the embryo and foetus. Cycle The endometrial lining undergoes cyclic
regeneration. Humans and the great apes display the menstrual cycle, whereas most other mammals are subject to an estrous cycle. In both cases, the endometrium initially proliferates under the influence of estrogen. However, once ovulation occurs, in addition to estrogen, the ovary will also
start to produce progesterone. This changes the proliferative pattern of the
endometrium to a secretory lining.
Eventually, the secretory lining provides a
hospitable environment for one or more
blastocysts. If a blastocyst implants, then
the lining remains as decidua. The decidua becomes part of the placenta; it provides
support and protection for the gestation. If there is inadequate stimulation of the
lining, due to lack of hormones, the
endometrium remains thin and inactive. In
humans, this will result in amenorrhea. After menopause, the lining is often described as being atrophic. In contrast,
endometrium that is chronically exposed to
estrogens, but not to progesterone, may
become hyperplastic. Long-term use of oral contraceptives with highly potent progesterone can also induce endometrial atrophy.[1][2] In humans, the cycle of building and
shedding the endometrial lining lasts an
average of 28 days. The endometrium
develops at different rates in different
mammals. Its formation is sometimes
affected by seasons, climate, stress, and other factors. The endometrium itself
produces certain hormones at different points along the cycle. This affects other
portions of the reproductive system . Histology High magnification micrograph of decidualized endometrium due to exogenous progesterone (oral contraceptive pill). H&E stain. Low magnification micrograph of decidualized endometrium. H&E stain. The endometrium consists of a single layer
of columnar epithelium resting on the stroma, a layer of connective tissue that varies in thickness according to hormonal influences. Simple tubular uterine glands reach from the endometrial surface
through to the base of the stroma, which
also carries a rich blood supply of spiral arteries. In a woman of reproductive age, two layers of endometrium can be
distinguished. These two layers occur only
in endometrium lining the cavity of the
uterus, not in the lining of the Fallopian tubes:[3] The functional layer is adjacent to the
uterine cavity. This layer is built up after
the end of menstruation during the first
part of the previous menstrual cycle. Proliferation is induced by estrogen (follicular phase of menstrual cycle), and
later changes in this layer are
engendered by progestrone from the corpus luteum (luteal phase). It is adapted to provide an optimum
environment for the implantation and
growth of the embryo. This layer is completely shed during menstruation. The basal layer, adjacent to the myometrium and below the functional layer, is not shed at any time during the
menstrual cycle, and from it the
functional layer develops. In the absence of progesterone, the
arteries supplying blood to the functional
layer constrict, so that cells in that layer
become ischaemic and die, leading to menstruation. It is possible to identify the phase of the
menstrual cycle by observing histological
differences at each phase: Phase Days Thickness Epithelium menstrual
phase 1-4 thin absent proliferative
phase 4-14 intermediate columnar secretory
phase 15-28 thick columnar.
Also
visible are helicine
branches
of uterine
artery Chorionic tissue can result in marked endometrial changes, known as an Arias- Stella reaction, that have an appearance similar to cancer.[4] Historically, this change was diagnosed as endometrial cancer and it is important only in so far as it should not be misdiagnosed as cancer. Pathological conditions Adenomyosis is the growth of the endometrium into the muscle layer of the
uterus (the myometrium). Endometriosis is the growth of endometrial tissue outside the uterus. Endometrial cancer is the most common cancer of the human female genital tract. Asherman's syndrome , also known as intrauterine adhesions occurs when the basal layer of the endometrium is
damaged by instrumention (e.g. D&C) or infection (e.g. endometrial tuberculosis) resulting in endometrial sclerosis and
adhesion formation partially or completely
obliterating the uterine cavity. Thin endometrium may be defined as an
endometrial thickness of less than 8 mm. It
usually occurs after menopause. Treatments that can improve endometrial
thickness include Vitamin E, L-arginine and sildenafil citrate.[5] Gene expression profiling using cDNA microarray can be used for the diagnosis of endometrial disorders.
FALLOPIAN TUBES
The Fallopian tubes, also known as oviducts, uterine tubes, and salpinges (singular salpinx) are two very fine tubes lined with ciliated epithelia, leading from the ovaries of female mammals into the uterus, via the utero-tubal junction. In non- mammalian vertebrates, the equivalent
structures are the oviducts. Anatomy and histology In a woman's body the tube allows
passage of the egg from the ovary to the
uterus. Its different segments are (lateral
to medial): the infundibulum with its associated fimbriae near the ovary, the ampullary region that represents the major portion of the lateral tube, the isthmus which is the narrower part of the tube that
links to the uterus, and the interstitial (also
intramural) part that transverses the
uterine musculature. The tubal ostium is the point where the tubal canal meets the
peritoneal cavity, while the uterine
opening of the Fallopian tube is the
entrance into the uterine cavity, the utero- tubal junction. There are two types of cells within the
simple columnar epithelium of the
Fallopian tube (oviduct). Ciliated cells
predominate throughout the tube, but are
most numerous in the infundibulum and
ampulla. Estrogen increases the production of cilia on these cells. Interspersed
between the ciliated cells are peg cells, which contain apical granules and produce
the tubular fluid. This fluid contains
nutrients for spermatozoa, oocytes, and zygotes. The secretions also promote capacitation of the sperm by removing glycoproteins and other molecules from the plasma membrane of the sperm. Progesterone increases the number of peg cells, while estrogen increases their height
and secretory activity. Tubal fluid flows
against the action of the ciliae, that is
toward the fimbrated end. Function in fertilization When an ovum is developing in an ovary, it is encapsulated in a sac known as an ovarian follicle. On maturity of the ovum, the follicle and the ovary's wall rupture,
allowing the ovum to escape. The egg is caught by the fimbriated end and travels to
the ampulla where typically the sperm are
met and fertilization occurs; the fertilized ovum, now a zygote, travels towards the uterus aided by activity of tubal cilia and
activity of the tubal muscle. After about
five days the new embryo enters the uterine cavity and implants about a day later. The release of a mature egg does not
alternate between the two ovaries and
seems to be random. After removal of an
ovary, the remaining one produces an egg every month. [1] Occasionally the embryo implants into the
Fallopian tube instead of the uterus, creating an ectopic pregnancy, commonly known as a "tubal pregnancy". Patency testing While a full testing of tubal functions in
patients with infertility is not possible, testing of tubal patency is important as tubal obstruction is a major cause of infertility. A hysterosalpingogram will demonstrate that tubes are open when the
radio-opaque dye spills into the uterine
cavity. Tubal insufflation is a standard procedure for testing patency. During
surgery the condition of the tubes may be
inspected and a dye such as methylene blue can be injected into the uterus and shown to pass through the tubes when the
cervix is occluded. As tubal disease is often
related to Chlamydia infection, testing for Chlamydia antibodies has become a cost- effective screening device for tubal pathology.[2] Embryology and homology Embryos have two pairs of ducts to let gametes out of the body; one pair (the Müllerian ducts) develops in females into the Fallopian tubes, uterus and vagina, while the other pair (the Wolffian ducts) develops in males into the epididymis and vas deferens. Normally, only one of the pairs of tubes
will develop while the other regresses and
disappears in utero. The homologous organ in the male is the
rudimentary appendix testis. Pathology Pelvic inflammatory disease can strike the fallopian tubes. This might cause a Fallopian tube obstruction. Fallopian tube cancer is a rare neoplasm that can arise from the epithelial lining of the Fallopian tube. This cancer is sometimes misdiagnosed as ovarian cancer.[3] However, treatment of both ovarian and
Fallopian tube cancer is similar. Surgery The surgical removal of a Fallopian tube is
called a salpingectomy. To remove both sides is a bilateral salpingectomy. An
operation that combines the removal of a
Fallopian tube with removal of at least one
ovary is a salpingo-oophorectomy. An operation to restore a fallopian tube
obstruction is called a tuboplasty. Etymology and nomenclature They are named after their discoverer, the
16th century Italian anatomist, Gabriele Falloppio. Though the name 'Fallopian tube' is
eponymous, some texts spell it with a
lower case 'f' from the assumption that the
adjective 'fallopian' has been absorbed
into modern English as the de facto name
for the structure. The Greek word salpinx (σαλπιγξ) means "trumpet".
UTEROTUBAL JUNCTION
The Uterotubal junction or Utero-tubal junction is the connection between the endometrial cavity of the uterus and the fallopian tube at the proximal tubal opening, the beginning of the intramural
part of the fallopian tube. Histologically ,
the endometrial epithelium changes over to the ciliated tubal epithelium. Function Patency of the utero-tubal junction is
necessary for normal reproduction. The
tubes can get blocked here by infection
(salpingitis) and surgical intervention. Mouse studies have indicated that selective
passage of individual spermatozoa may occur at this junction,[1], with abnormal morphology being identified as a
significant selection criterion, leading to
predominantly normal sperm passing towards the ovum.[2]. Absence of the protein calmegin has also been suggested as a critical factor for reliable sperm passage.[1] Other The utero-tubal junction is accessible by hysteroscopy and the entry point for tubal cannulation and falloposcopy. Contraceptive methods have been
developed to block the utero-tubal
junction.
PELVIS
The pelvis is an anatomical structure found in humans (see human pelvis) or in animals. It contains a large compound bone
structure at the base of the spine, which is
connected with the legs or rear limbs. This
bony structure is called the pelvis skeleton or bony pelvis, and consists of hip bone, sacrum and coccyx. The synsacrum is a skeletal structure, mainly described in birds and dinosaurs.
BROAD LIGAMENTS
The broad ligament of the uterus is the wide fold of peritoneum that connects the sides of the uterus to the walls and floor of the pelvis. Subdivisions The broad ligament may be divided into three subcomponents:[1] Mesometrium - the mesentery of the uterus; the largest portion of the broad
ligament Mesosalpinx - the mesentery of the Fallopian tube Mesovarium - the mesentery of the ovaries. Contents The contents of the broad ligament include the following:[2] Reproductive Uterine tubes (or Fallopian tube) ovary (some sources consider the
ovary to be on the broad ligament, but not in it.)[3] vessels ovarian artery (in the suspensory ligament)[4] uterine artery ligaments ovarian ligament round ligament of uterus suspensory ligament of the ovary (Some sources consider it a part of
the broad ligament while other
sources just consider it a "termination" of the ligament.[5]) Structure The peritoneum surrounds the uterus like a flat sheet that is folded over the uterus; on
the sides of the uterus, this sheet of
peritoneum comes in direct contact with
itself, forming the double layer of
peritoneum known as the broad ligament
of the uterus. The part where this peritoneal sheet is
folded (i.e. the free edge) has the uterine tubes running between the two layers; this part is known as the mesosalpinx. Function The broad ligament serves as a mesentery
for the uterus, ovaries, and the uterine
tubes. It helps in maintaining the uterus in
its position,but it is not a major
contributing factor.
UTEROSACRAL LIGAMENTS
The uterosacral ligaments (or recto- uterine ligament) belongs to the major ligaments of uterus. The rectouterine folds contain a considerable amount of fibrous tissue and
non-striped muscular fibers which are
attached to the front of the sacrum and constitute the uterosacral ligaments.
CARDINAL LIGAMENTS
Cardinal ligament Vessels of the uterus and its appendages, rear view. (Cardinal ligament not visible, but location can be inferred from position of uterine artery and uterine vein.) Uterus and right broad ligament, seen from behind. (Cardinal ligament not labeled, but broad ligament visible at center.) Latin ligamentum cardinale, ligamentum
transversum cervicis, ligamentum
transversalis colli Gray's subject #268 1261 The cardinal ligament (or Mackenrodt's ligament[1], lateral cervical ligament, or transverse cervical ligament[2]) is a major ligament of the uterus. It is located at the base of the broad ligament of the uterus. Importantly, it contains the uterine artery and uterine vein. There is a pair of cardinal ligaments in the female human body. It attaches the cervix to the lateral pelvic wall at the ischial spine, and is continuous externally with the fibrous tissue that
surrounds the pelvic blood vessels. It thus provides support to the uterus.[3] It may be of clinical significance in hysterectomy,[4][5] due to its close proximity to the ureters, which can get
damaged during ligation of the ligament.
CERVIX
The cervix (or neck of the uterus) is the lower, narrow portion of the uterus where it joins with the top end of the vagina. It is cylindrical or conical in shape and
protrudes through the upper anterior
vaginal wall. Approximately half its length
is visible with appropriate medical
equipment; the remainder lies above the
vagina beyond view. It is occasionally called "cervix uteri". Cervix means neck in
Latin. AnatomyThe cervix with cervical mucous The cervical os Ectocervix The portion projecting into the vagina is
referred to as the portio vaginalis or ectocervix. On average, the ectocervix is
3 cm long and 2.5 cm wide. It has a convex,
elliptical surface and is divided into
anterior and posterior lips. External os Main article: External orifice of the uterus The ectocervix's opening is called the external os. The size and shape of the external os and the ectocervix varies
widely with age, hormonal state, and
whether the woman has had a vaginal
birth. In women who have not had a
vaginal birth the external os appears as a
small, circular opening. In women who have had a vaginal birth, the ectocervix
appears bulkier and the external os
appears wider, more slit-like and gaping. Endocervical canal The passageway between the external os
and the uterine cavity is referred to as the endocervical canal. It varies greatly in length and width, along with the cervix
overall. Flattened anterior to posterior, the
endocervical canal measures 7 to 8 mm at
its widest in reproductive-aged women. Internal os The endocervical canal terminates at the internal os which is the opening of the cervix inside the uterine cavity. Histology The epithelium of the cervix is varied. The ectocervix (more distal, by the vagina) is
composed of nonkeratinized stratified squamous epithelium. The endocervix (more proximal, within the uterus) is
composed of simple columnar epithelium. [1] The area adjacent to the border of the
endocervix and ectocervix is known as the
transformation zone. The Transformation
zone undergoes metaplasia numerous times during normal life. When the
endocervix is exposed to the harsh acidic
environment of the vagina it undergoes metaplasia to squamous epithelium which is better suited to the vaginal
environment. Similarly when the
ectocervix enters the less harsh uterine
area it undergoes metaplasia to become columnar epithelium. Times in life when this metaplasia of the transformation zone occurs: puberty; when the endocervix everts
(moves out) of the uterus with the changes of the cervix
associated with the normal menstrual
cycle post-menopause; the uterus shrinks
moving the transformation zone
upwards All these changes are normal and the
occurrence is said to be physiological. However, all this metaplasia does increase
the risk of cancer in this area - the
transformation zone is the most common
area for cervical cancer to occur. At certain times of life, the columnar
epithelium is replaced by metaplastic
squamous epithelium, and is then known
as the transformation zone. Nabothian cysts are often found in the cervix.[2] Cervical mucus Mucus plug Cervical Mucus is 90% water. Depending on
the water content which varies during the
menstrual cycle the mucus functions as a
barrier or a transport medium to
spermatoza. Cervical mucus also contains
electrolytes (calcium, sodium and potassium), organic components such as
glucose, amino acids and soluble proteins. [3] Cervical mucus contains trace elements
including zinc, copper, iron, mangenese and
selenium, the levels of which vary
dependant on cyclical hormone variation
during different phases of the menstrual cycle [4] Various enzymes have been identified in human cervical mucus.
Glycerol is a natural ingredient of human cervical fluid.[5][6][7][8] Studies have shown that the amount of glycerol in
cervical fluid increases during sexual excitement.[6] This increase in glycerol has been postulated to be responsible for the
lubricating quality of this fertile cervical
fluid and may be biologically relevant
during the early phase of reproductive
events. After a menstrual period ends, the external os is blocked by mucus that is thick and acidic. This "infertile" mucus blocks spermatozoa from entering the uterus.[9] For several days around the time of ovulation, "fertile" types of mucus are produced; they have a higher water
content, are less acidic, and have a ferning
pattern that helps guide spermatozoa through the cervix.[10] This ferning is a branching pattern seen in the mucus when
observed with low magnification. Some methods of fertility awareness involve estimating a woman's periods of
fertility and infertility by observing
changes in her body. Among these changes
are several involving the quality of her
cervical mucus: the sensation it causes at
the vulva, its elasticity ( Spinnbarkeit), its transparency, and the presence of ferning. [10] Cervical mucus Most methods of hormonal contraception work primarily by preventing ovulation,
but their effectiveness is increased
because they prevent the fertile types of
cervical mucus from being produced.
Conversely, methods of thinning the mucus
may help to achieve pregnancy. One suggested method is to take guaifenesin in the few days before ovulation. [11] During pregnancy the cervix is blocked by a
special antibacterial mucosal plug which prevents infection, somewhat similar to its
state during the infertile portion of the menstrual cycle. The mucus plug comes out as the cervix dilates in labor or shortly
before. Cervical position After menstruation and directly under the
influence of estrogen, the cervix undergoes a series of changes in position and texture.
During most of the menstrual cycle, the
cervix remains firm, like the tip of the
nose, and is positioned low and closed.
However, as a woman approaches
ovulation, the cervix becomes softer, and rises and opens in response to the high levels of estrogen present at ovulation. [12] These changes, accompanied by the
production of fertile types of cervical
mucus, support the survival and movement
of sperm. Function During menstruation the cervix stretches open slightly to allow the endometrium to be shed. This stretching is believed to be
part of the cramping pain that many women experience. Evidence for this is
given by the fact that some women's
cramps subside or disappear after their
first vaginal birth because the cervical
opening has widened. During childbirth, contractions of the uterus will dilate the cervix up to 10 cm in diameter to allow the child to pass through. During orgasm, the cervix convulses and the external os dilates. Robin Baker and Mark A. Bellis, both at the University of Manchester, first proposed that this behavior would tend to draw semen in the vagina into the uterus, increasing the likelihood of conception.[13] This explanation has been called the "upsuck
theory of female orgasm." Komisaruk,
Whipple, and Beyer-Flores, in their book,
The Science of Orgasm, claimed there is
evidence in support of the upsuck theory. [14] Science historian Elisabeth Lloyd, author of The Case of the Female Orgasm,
questioned the logic of this theory and the
quality of the experimental data used to back it,[15] commenting in 2005: "[The upsuck theory] has been widely accepted
in the community of scientists for the past
12 years... But unfortunately the evidence
for it is really badly flawed. In one of their
tables 73% of the data came from one
woman. It's really quite shocking that for 12 years this research has been taught as
"fact" all across the US, Canada and the UK."[16] Short cervix[17] is the strongest predictor of preterm birth.[18][19][20] Some treatments to prevent cervical cancer, such
as LEEP, cold-knife conization, or cryotherapy may shorten the cervix. Cervical cancer Main article: Cervical cancer Human papillomavirus (HPV) infection is a necessary factor in the development of
nearly all cases of cervical cancer. HPV vaccines can reduce the chance of developing cervical cancer, if administered
before initiation of sexual activity.
Potentially pre-cancerous changes in the
cervix can be detected by a Pap smear, in which epithelial cells are scraped from the surface of the cervix and examined under a microscope. With appropriate treatment of detected abnormalities, cervical cancer can
be prevented. Most women who develop
cervical cancer have never had a Pap
smear, or have not had one within the last
five years. Worldwide, cervical cancer is the fifth most deadly cancer in women. [21] It affects about 16 per 100,000 women per year and kills about 9 per 100,000 per year.[22] Pap smear screening has greatly reduced
cervical cancer incidence and mortality in
nations with regular screening programs. Lymphatic drainage The lymphatic drainage of the cervix is along the uterine arteries and cardinal ligaments to the parametrial, external iliac vein, internal iliac vein, and obturator and presacral lymph nodes. From these pelvic lymph nodes, drainage then proceeds to
the paraaortic lymph nodes. In some women, the lymphatics drain directly to
the paraaortic nodes.
UTERUS
The uterus (from Latin "uterus", plural uteri or "uteruses") or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species. It is within the uterus that the fetus develops during gestation, usually developing completely in placental mammals such as humans and partially in marsupials such as kangaroos and opossums. Two uteruses usually form initially in a female fetus, and in placental
mammals they may partially or completely
fuse into a single uterus depending on the
species. In many species with two
uteruses, only one is functional. Humans
and other higher primates such as chimpanzees, along with horses, usually have a single completely fused uterus,
although in some individuals the uteruses
may not have completely fused. The term
uterus is used consistently within the
medical and related professions, while the
Germanic derived term womb is also common in everyday usage in the English language. Most animals that lay eggs, such as birds and reptiles, have an oviduct instead of a uterus. In monotremes, mammals which lay eggs and include the platypus, either the term uterus or oviduct is used to
describe the same organ, but the egg does
not develop a placenta within the mother and thus does not receive further
nourishment after formation and fertilization. Marsupials have two uteruses, each of which connect to a lateral vagina
and which both use a third, middle
"vagina" which functions as the birth
canal. Marsupial embryos form a choriovitelline "placenta" (which can be
thought of as something between a
monotreme egg and a "true" placenta), in
which the egg's yolk sac supplies a large
part of the embryo's nutrition but also
attaches to the uterine wall and takes nutrients from the mother's bloodstream. Function The uterus consists of a body and a cervix.The cervix protrudes into the vagina. The uterus is held in position within the
pelvis by condensations of endopelvic
fascia, which are called ligaments. These
ligaments include the pubocervical,
transverse. cervical ligaments cardinal ligaments, and the uterosacral ligaments. It is covered by a sheet-like fold of peritoneum, the broad ligament.[1] The uterus is essential in sexual response by directing blood flow to the pelvis and to the external genitalia, including the ovaries, vagina, labia, and clitoris. The reproductive function of the uterus is
to accept a fertilized ovum which passes through the utero-tubal junction from the fallopian tube. It implants into the endometrium, and derives nourishment from blood vessels which develop
exclusively for this purpose. The fertilized
ovum becomes an embryo, attaches to a
wall of the uterus, creates a placenta, and
develops into a fetus (gestates) until childbirth. Due to anatomical barriers such as the pelvis, the uterus is pushed partially into the abdomen due to its expansion
during pregnancy. Even during pregnancy
the mass of a human uterus amounts to
only about a kilogram (2.2 pounds). Forms in mammals In mammals, the four main forms in which
it is found are: Duplex There are two wholly separate uteri,
with one fallopian tube each. Found in marsupials (such as kangaroos, Tasmanian devils, opossums, etc.), rodents (such as mice, rats, and guinea pigs), and lagomorpha (rabbits and hares). Bipartite The two uteri are separate for most of
their length, but share a single cervix.
Found in ruminants (deer, moose, elk etc.), and cats. Bicornuate The upper parts of the uterus remain
separate, but the lower parts are fused
into a single structure. Found in dogs, pigs, elephants, whales, dolphins, and prosimian primates among others. Simplex The entire uterus is fused into a single
organ. Found in higher primates (including humans and chimpanzees) .
Occasionally, some individual females
(including humans) may have a bicornuate uterus, a uterine malformation where the two parts of the uterus fail to fuse completely during
fetal development. In monotremes such as the platypus, the uterus is duplex and rather than nurturing
the embryo, secretes the shell around the
egg. It is essentially identical with the shell gland of birds and reptiles, with which the uterus is homologous.[2] Anatomy The uterus is located inside the pelvis immediately dorsal (and usually somewhat rostral) to the urinary bladder and ventral to the rectum. The human uterus is pear- shaped and about 3 in. (7.6 cm) long. A
female's uterus can be divided
anatomically into four segments: The
fundus, corpus, cervix and the internal os. Regions From outside to inside, the path to the
uterus is as follows: Cervix uteri - "neck of uterus" External orifice of the uterus Canal of the cervix Internal orifice of the uterus corpus uteri - "Body of uterus" Cavity of the body of the uterus Fundus (uterus) Layers The layers, from innermost to outermost,
are as follows: Endometrium The lining of the uterine cavity is called
the "endometrium". It consists of the
functional endometrium and the basal
endometrium from which the former
arises. Damage to the basal
endometrium results in adhesion formation and/or fibrosis (Asherman's syndrome). In all placental mammals, including humans, the endometrium
builds a lining periodically which is shed
or reabsorbed if no pregnancy occurs. Shedding of the functional endometrial
lining is responsible for menstrual bleeding (known colloquially as a "period" in humans with a cycle of
about 28 days) throughout the fertile
years of a female and for some time
beyond. Depending on the species,
menstrual cycles may vary from a few
days to six months, but can vary widely even in the same individual, often
stopping for several cycles before
resuming. Marsupials and monotremes
do not have menstruation. Myometrium The uterus mostly consists of smooth muscle, known as "myometrium." The innermost layer of myometrium is
known as the junctional zone, which becomes thickened in adenomyosis. Parametrium The loose connective tissue around the
uterus. Perimetrium The peritoneum covering of the fundus
and ventral and dorsal aspects of the
uterus. Support The uterus is primarily supported by the pelvic diaphragm, perineal body and the urogenital diaphragm. Secondarily, it is supported by ligaments and the peritoneum (broad ligament of uterus)[3] Axes Normally the uterus lies in anteversion &
anteflexion.Antiversion is a forward angle
between the axis of the cervix and that of
the vagina measuring about 90
degree,provided the urinary bladder and
the rectum are empty.Antiflexion is a forward angle between the body and
cervix at the isthmus measuring about 125
degree,provided the bladder and rectum
are empty. Major ligaments It is held in place by several peritoneal ligaments, of which the following are the most important (there are two of each): Name From To Uterosacral
ligament Posterior
cervix Anterior face
of sacrum Cardinal
ligaments Side of the
cervix Ischial spines Pubocervical ligament[3] Side of the
cervix Pubic
symphysis Position The uterus is in the middle of the pelvic
cavity in frontal plane (due to ligamentum latum uteri). The fundus does not surpass the linea terminalis, while the vaginal part of the cervix does not extend below
interspinal line. The uterus is mobile and
moves under the pressure of the full
bladder or full rectum anteriorly, whereas
if both are full it moves upwards.
Increased intraabdominal pressure pushes it downwards. The mobility is conferred to
it by musculo-fibrous apparatus that
consists of suspensory and sustentacular
part. Under normal circumstances the
suspensory part keeps the uterus in
anteflexion and anteversion (in 90% of women) and keeps it "floating" in the
pelvis. The meaning of these terms are
described below: Distinction More common Less common Position
tipped "Anteverted":
Tipped
forward "Retroverted": Tipped
backwards Position of
fundus "Anteflexed":
Fundus is
pointing
forward
relative to the
cervix "Retroflexed":
Fundus is
pointing
backwards Sustentacular part supports the pelvic
organs and comprises the larger pelvic diaphragm in the back and the smaller urogenital diaphragm in the front. The pathological changes of the position of
the uterus are: retroversion/retroflexion, if it is fixed hyperanteflexion - tipped too forward;
most commonly congenital, but may be
caused by tumors anteposition, retroposition,
lateroposition - the whole uterus is
moved; caused by parametritis or tumors elevation, descensus, prolapse rotation (the whole uterus rotates
around its longitudinal axis), torsion
(only the body of the uterus rotates
around) inversion In cases where the uterus is "tipped", also
known as retroverted uterus, women may have symptoms of pain during sexual
intercourse, pelvic pain during
menstruation, minor incontinence, urinary
track infections, problems trying to
conceive, and difficulty using tampons. A
pelvic examination by a doctor can determine if a uterus is tipped.[4] Blood supply Vessels of the uterus and its appendages, rear view. Schematic diagram of uterine arterial vasculature seen as a cross-section through the myometrium and endometrium. The uterus is supplied by arterial blood
both from the uterine artery and the ovarian artery. Development The bilateral Müllerian ducts form during early fetal life. In males, MIF secreted from the testes leads to their regression. In
females these ducts give rise to the Fallopian tubes and the uterus. In humans the lower segments of the two ducts fuse
to form a single uterus, however, in cases
of uterine malformations this development may be disturbed. The different uterine
forms in various mammals are due to
various degrees of fusion of the two
Müllerian ducts. Pathology Some pathological states include: Prolapse of the uterus Carcinoma of the cervix – malignant neoplasm Carcinoma of the uterus – malignant neoplasm Fibroids – benign neoplasms Adenomyosis – ectopic growth of endometrial tissue within the
myometrium Pyometra – infection of the uterus, most commonly seen in dogs Uterine malformations mainly congenital malformations including Uterine Didelphys, bicornuate uterus and septate uterus. It also includes
congenital absence of the uterus Rokitansky syndrome Asherman's syndrome , also known as intrauterine adhesions occurs when the basal layer of the endometrium is
damaged by instrumention (e.g. D&C) or infection (e.g. endometrial tuberculosis) resulting in endometrial scarring
followed by adhesion formation which
partially or completely obliterates the
uterine cavity.
FEMALE GENITAL SYSTEM
The female reproductive system (or female genital system) contains two main parts: the uterus, which hosts the developing fetus, produces vaginal and
uterine secretions, and passes the
anatomically male person's sperm through to the fallopian tubes; and the ovaries, which produce the anatomically female
person's egg cells. These parts are internal;
the vagina meets the external organs at
the vulva , which includes the labia, clitoris and urethra. The vagina is attached to the uterus through the cervix, while the uterus is attached to the ovaries via the Fallopian tubes. At certain intervals, the ovaries release an ovum, which passes through the Fallopian tube into the uterus. If, in this transit, it meets with sperm, the sperm penetrate and merge with the egg, fertilizing it. The fertilization usually occurs in the oviducts, but can happen in the uterus itself. The zygote then implants itself in the wall of the uterus, where it
begins the processes of embryogenesis and morphogenesis. When developed enough to survive outside the womb, the cervix dilates and contractions of the uterus
propel the fetus through the birth canal, which is the vagina. The ova are larger than sperm and have formed by the time an anatomically female
person is born. Approximately every
month, a process of oogenesis matures one ovum to be sent down the Fallopian tube attached to its ovary in anticipation of fertilization. If not fertilized, this egg is flushed out of the system through menstruation. Embryonic development Chromosome characteristics determine the
genetic sex of a child at conception. This is specifically based on the 23rd pair of
chromosomes that is inherited. Since the
mother's egg contains an X chromosome
and the father's sperm contains either an X
or Y chromosome, it is the male who determines the baby's sex. If the baby
inherits the X chromosome from the father,
the baby will be an anatomically female
person. In such case, testosterone is not made, but the Wolffian duct will degrade
and the Müllerian duct will develop into
female sex organs. In this case, the female clitoris is the remnants of the Wolffian duct. On the other hand, if the baby inherits
the Y chromosome from the father, the
baby will be an anatomically male person.
In such case, testosterone will be in charge
of stimulating the Wolffian duct in order to
develop male sex organs, and the Müllerian duct will degrade.[1] Internal An anatomically female person's internal
reproductive organs are the vagina, uterus,
fallopian tubes, cervix and ovary. Vagina Main article: Vagina The vagina is a fibro muscular tubular tract leading from the uterus to the exterior of the body in female mammals, or to the cloaca in female birds and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the oviduct. The vagina is the place where semen from the anatomic male is deposited into the
anatomically female person's body at the
climax of sexual intercourse, commonly known as ejaculation. Around the vagina, pubic hair protects the vagina from
infection and is a sign of puberty. The
vagina is mainly used for sexual
intercourse. Cervix Main article: Cervix The cervix is the lower, narrow portion of the uterus where it joins with the top end of the vagina. It is cylindrical or conical in shape and protrudes through the upper
anterior vaginal wall. Approximately half
its length is visible, the remainder lies
above the vagina beyond view. The vagina
has a thick layer outside and it is the
opening where baby comes out during delivery. The cervix is also called the neck
of the uterus. Uterus Main article: Uterus The uterus or womb is the major female reproductive organ of humans. The uterus provides mechanical protection, nutritional
support, and waste removal for the
developing embryo (weeks 1 to 8) and
fetus (from week 9 until the delivery). In
addition, contractions in the muscular wall
of the uterus are important in pushing out the fetus at the time of birth. The uterus contains three suspensory
ligaments that help stabilize the position
of the uterus and limits its range of
movement. The uterosacral ligaments,
keep the body from moving inferiorly and
anteriorly. The round ligaments, restrict posterior movement of the uterus. The
cardinal ligaments, also prevent the
inferior movement of the uterus. The uterus is a pear-shaped muscular organ. Its major function is to accept a
fertilized ovum which becomes implanted into the endometrium, and derives nourishment from blood vessels which
develop exclusively for this purpose. The
fertilized ovum becomes an embryo, develops into a fetus and gestates until childbirth. If the egg does not embed in the wall of the uterus, an anatomically female
person begins menstruation and the egg is flushed away. Oviducts Main article: Fallopian tube The Fallopian tubes or oviducts are two tubes leading from the ovaries of female mammals into the uterus. On maturity of an ovum, the follicle and the ovary's wall rupture, allowing the ovum to escape and enter the Fallopian tube. There it travels toward the uterus, pushed along
by movements of cilia on the inner lining of the tubes. This trip takes hours or days.
If the ovum is fertilized while in the Fallopian tube, then it normally implants in the endometrium when it reaches the uterus, which signals the beginning of pregnancy. Ovaries Main article: Ovary The ovaries are small, paired organs that
are located near the lateral walls of the
pelvic cavity. These organs are responsible
for the production of the ova and the
secretion of hormones. Ovaries are the place inside the anatomically female body
where ova or eggs are produced. The process by which the ovum is released is called ovulation. The speed of ovulation is periodic and impacts directly to the length of a menstrual cycle. After ovulation, the ovum is captured by the oviduct, after traveling down the oviduct to the uterus, occasionally being fertilized on its way by an incoming sperm, leading to pregnancy and the eventual birth of a new human being. The Fallopian tubes are often called the oviducts and they have small hairs ( cilia) to help the egg cell travel. Reproductive tract The reproductive tract (or genital tract) is
the lumen that starts as a single pathway through the vagina, splitting up into two lumens in the uterus, both of which continue through the Fallopian tubes, and ending at the distal ostia that open into the abdominal cavity. In the absence of fertilization, the ovum will eventually traverse the entire
reproductive tract from the fallopian tube
until exiting the vagina through menstruation. The reproductive tract can be used for
various transluminal procedures such as fertiloscopy, intrauterine insemination and transluminal sterilization. External The external components include the mons pubis, pudendal cleft, labia majora, labia minora, Bartholin's glands, and clitoris. Female genital modification There are surgical procedures intended to
change an anatomically female person's
sexual appearance. The clitoral hood
reduction, also known as clitoridotomy, is a
procedure intended to reposition the
protruding clitoris and reduce the length and projection of the clitoral hood. The
procedure is also indicated in those women
with mild clitoral enlargement unwilling to undergo a formal clitoris reduction.[2] The clitoral hood removal, also known as
hoodectomy, is a cosmetic surgery intended to enhance an anatomically
female person's sexual experience. This
surgery involves the trimming back of the
clitoral hood or a complete clitoris hood removal.[3] Removal of the protective hood allows for more clitoral exposure which
increases sensitivity in the clitoris. This
procedure, sometimes called female
circumcision, is different from a clitoral
excision and is not intended to prevent a
woman from experiencing sexual pleasure. [4] Another surgical procedure is the clitoral
reduction. Clitoris may enlarge due to
hormonal abnormalities, ingestion of steroids, or birth. Surgery can reduce the glans or shaft of the clitoris through an outpatient procedure.[5] According to WHO, female genital mutilation (FGM) comprises all those
procedures that involve partial or total
removal of the external female genitalia as
well as other injury to the female genital organs for non-medical reasons.[6] Contrary to surgical procedures intended to
enhance a woman's sexual experience or
her physical appearance, female genital
mutilation does not have health benefits
and it actually can be very harmful. This
kind of procedure may have several complications from severe bleeding, tetanus or sepsis, urine retention, open sores in the genital area and damage to
the tissue to potential childbirth complications, infertility, and newborn deaths. This practice is common in the
western, eastern and north-eastern
regions of Africa. It also takes place in some countries in Asia and the Middle East. It is also known that the procedure is
practiced by some immigrant communities in North America and Europe.