Vagina Connecting the internal and external genitalia is a fibro- muscular tube called the vagina. The vagina, which is essentially free of sensory nerve fibers, is located behind the urinary bladder and urethra and anterior to the rectum.

The uterine cervix projects into the vagina at its upper end, forming recesses called fornices.

The vagina functions as a route for discharge of menses and other secretions.

It also serves as an organ of sexual fulfillment and reproduction.

The membranous vaginal wall forms two longitudinal folds and several transverse folds, or rugae.

The vagina is lined with mucus-secreting stratified squamous epithelial cells.

Vaginal tissue usually is moist, with a pH maintained within the bacteriostatic range of 3.8 to 4.2.

The epithelial cells of the vagina, like other tissues of the reproductive system, respond to changing levels of the ovarian sex hormones.

Estrogen stimulates the proliferation and maturation of the vaginal mucosa; this results in a thickening of the vaginal mucosa and an increased glycogen content of the epithelial cells.

The glycogen is fermented to lactic acid by the lactobacilli (i.e., Doderlein's bacilli) that are part of the normal vaginal flora, accounting for the mildly acid pH of vaginal fluid.

The vaginal ecology can be disrupted at many levels, rendering it susceptible to infection.

Pregnancy and the use of oral contraceptive agents increase the amount of estrogen in the system.

Diabetes or a pre-diabetic state may increase the glycogen content of the cells.

The use of systemic antibiotics may decrease the number of lactobacilli in the vagina.

Decreased estrogen stimulation after menopause causes the vaginal mucosa to become thin and dry, often resulting in dyspareunia (i.e., painful intercourse);atrophic vaginitis, and occasionally in vaginal bleeding.

Estrogen levels can be estimated by means of vaginal scrapings obtained during a routine pelvic examination.

The scrapings are used for a test, known as the maturation index, which examines the cellular structure and configuration of the vaginal epithelial cells.

The maturation index determines the ratio of parabasal (least mature), intermediate, and superficial (most mature) cells.

Typically, this index is 0-40-60 during the reproductive years.

With diminished estrogen levels, there is a shift to the left, producing an index of 30-40-30 during the perimenopausal period and an index of 75-25-0 during the postmenopausal period.

Referrence:Female External Genitalia||Female Internal Genitalia(Chinese Version)

Vagina

The vagina extends from the vaginal opening to the cervix, the opening to the uterus. The vagina serves as the receptacle for the penis during sexual intercourse, and as the birth canal through which the baby passes during labor. The average vaginal canal is three inches long, possibly four in women who have given birth. This may seem short in relation to the penis, but during sexual arousal the cervix will lift upwards and the fornix (see illustration) may extend upwards into the body as long as necessary to receive the penis. After intercourse, the contraction of the vagina will allow the cervix to rest inside the fornix, which in its relaxed state is a bowl-shaped fitting perfect for the pooling of semen.

At either side of the vaginal opening are the Bartholin's glands, which produce small amounts of lubricating fluid, apparently to keep the inner labia moist during periods of sexual excitement. Further within are the hymen glands, which secrete lubricant for the length of the vaginal canal.

"G-Spot"

The word is in quotes because there is still some debate as to the existance or purpose of the G- spot. In the illustration above, what is indicated as the g-spot in fact points to a region known as the Skenes glands, the purpose of which are unknown. Despite the controversy, one fact remains-- there are many women who claim that pressure on this region of the vagina is extremely pleasurable. Usually, two fingers are used, and because the spot is deep within the tissue, some pressure may be needed. Also, because the Skenes glands are alongside the bladder, some women may found that the increased pressure makes them feel as if they need to urinate.

Cervix

The cervix is the opening to the uterus. It varies in diameter from 1 to 3 millimeters, depending upon the time in the menstrual cycle the measurement is taken. The cervix is sometimes plugged with cervical mucous to protect the cervix from infection; during ovulation, this mucous becomes a thin fluid to permit the passage of sperm.

Uterus

The uterus, or womb, is the main female internal reproductive organ. The inner lining of the uterus is called the endometrium, which grows and changes during the menstrual cycle to prepare to receive a fertilized egg, and sheds a layer at the end of every menstrual cycle if fertilization does not happen. The utereus is lined with powerful muscles to push the child out during labor.

Ovaries

The ovaries perform two functions: the production of estrogen and progesterone, the female sex hormones, and the production of mature ova, or eggs. At birth, the ovaries contain nearly 400,000 ova, and those are all she will ever have. However, that is far more than she will need, since during an average lifespan she will go through about 500 menstrual cycles. After maturing, the single egg travels down the fallopian tube, a journey of three or four days-- this is the period during which a woman is fertile and pregnancy may occur. Eggs that are not fertilized are expelled during menstruation.