From Wikipedia, the free encyclopedia
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 incorrectly used to refer to the vulva or female genitals generally; strictly speaking, the vagina is a specific internal structure.
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 the stimulation of the clitoris, the walls of the vagina self-lubricate. This reduces friction that can be caused as a result of various sexual activities. 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.(10 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 inserted penis or other object.
An erogenous zone referred to commonly 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. Some researchers deny the existence of the G-spot.
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.
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.