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The vagina, (from Latin, 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 (rarely used in English) is vaginae.
In common speech, the term "vagina" is often used to refer to the vulva or female genitals generally; strictly speaking, the vagina is a specific internal structure and the vulva is the exterior genitalia only.
The human vagina is an elastic muscular canal that extends from the cervix to the vulva. Although there is wide anatomical variation, the length of the unaroused vagina 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). During sexual arousal the vagina expands in both length and width. Its elasticity allows it to stretch during sexual intercourse and during birth to offspring. 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 rectouterine pouch. Above the vagina is Mons Veneris. The vagina, along with the inside of the vulva, is reddish pink in color, as with most healthy internal mucous membranes in mammals.
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 ofmucus, which provides a favorable alkaline environment in the vaginal canal to maximize the chance of surivival for sperm.
The hymen is a thin membrane of connective tissue which is situated at the opening of the vagina. As with many female animals, the hymen covers the opening of the vagina from birth until it is ruptured during activity. The hymen may rupture during sexual or non-sexual activity. Vaginal penetration may rupture the hymen. A pelvic examination, injury, or certain types of exercises, such as horseback riding or gymnastics may also rupture the hymen. Sexual intercourse does not always rupture the hymen. Therefore, the presence or absence of a hymen does not indicate virginity or prior sexual activity.
Physiological functions of the vagina
The vagina has several biological functions.
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 stimulation of the clitoris, the walls of the vagina self-lubricate, reducing friction during sexual activity. Research has found that portions of the clitoris extend into the vulva and vagina.
With arousal, the vagina lengthens rapidly to an average of about 4 in.(8.5 cm), but can continue to lengthen in response to pressure. As the woman becomes fully aroused, the vagina tents (last ²⁄₃ expands in length and width) while the cervix retracts. The walls of the vagina are composed of soft elastic folds of mucous membrane skin which stretch or contract (with support from pelvic muscles) to the size of the penis. With proper arousal, the vagina may stretch/contract to accommodate virtually any penis size (or sex toy/object within reason).
An erogenous zone referred to commonly as the G-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. Some researchers deny the existence of the G-spot.
During childbirth, the vagina provides the channel to deliver the baby from the uterus to its independent life outside the body of the mother. During birth, the vagina is often referred to as the birth canal. The vagina is remarkably elastic and stretches to many times its normal diameter during vaginal birth.
Sexual health and hygiene
The vagina is self-cleansing and therefore usually needs no special treatment. Doctors generally discourage the practice of douching. 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 due to lactic acid secreted by symbiotic microorganisms retards the growth of many strains of dangerous microbes.
The vagina and popular culture
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Vagina". A list of authors is available in Wikipedia.|