Female Anatomy
The female external genitals are referred to as the vulva. Your vulva includes the labia majora (outer lips); the labia minora (inner lips); the tip of the clitoris; the urethral opening; and the vaginal opening. The two long fleshy folds of the outer lips are composed of fat and erectile tissue and covered with pubic hair. The smooth, hairless inner lips enclose the urethral and vaginal openings. The inner lips tend to be the most distinctive feature of the vulva, and they rarely come as a matched pair. Women’s labia vary greatly in size, shape, color, and the extent to which it protrudes from under the clitoral hood.
You can easily locate your clitoris, the most sensitive spot in your pubic area, tucked under the folds of skin where the top of the labia meet. Pull back the skin over the clitoris to reveal the clitoral glans. Above your glans, there is the clitoral shaft which feels like a short rod of cartilage directly beneath the skin. Underneath your skin, the clitoral shaft separates into two crura (legs) which extend (like a wishbone) for about three inches on either side of the vaginal opening. The entire clitoris consists of erectile tissue made up of blood vessels, spongy tissue, and nerves. The clitoris is the only organ in the human body whose sole function is to transmit sexual sensation. It is made up of approximately eight thousand nerve fibers, a higher concentration than in any other body part, and twice as many as in the penis.
Moving attention down from your clitoris toward your vaginal opening, you should be able to locate the urethra, the tube that conducts urine from the bladder out of the body. The urethral opening is more visible in some women than others. The spongy, acorn-shaped protrusion around the urethral opening is loaded with nerve endings and is an erogenous zone for many women.
Inside your body, the urethra runs parallel to and above the vagina, so that the ceiling of the vagina is closest to the floor of the urethra. The urethra is surrounded by spongy tissue dense with blood vessels and containing glands similar, in their makeup and in the fluids they produce, to the male prostate gland. These glands are most densely concentrated in an area equivalent to the outer third of the vagina. This urethral sponge is what has come to be called the G-spot, or female prostate.
The vaginal opening appears as folds of skin, rather than as an open space. The vagina is extremely expandable, yet most of the time the vaginal walls rest companionably against each other. The vagina is about four inches long. After the initial bulge over the urethral sponge, the vaginal canal curves back to the cervix, the neck of the uterus. The outer third of the vaginal walls consist of ridge and folds of tissue, has more nerve endings, and is more sensitive than the rest of the vagina. The inner two-thirds of the vaginal walls are smoother and contain fewer nerve endings—therefore, the inner part of the vagina is more responsive to pressure. Like the inner vagina, the cervix can be quite sensitive to pressure. During sexual arousal, the uterus elevates and the inner vagina balloons, creating a cul-de-sac of sorts behind the cervix.
Player 1: The Ovaries
Each month during our reproductive years, ten to twenty follicles begin maturing under the influence of hormones. Usually, only one follicle develops fully. Our bodies reabsorb the others before they complete development. Some of the cells in the follicle secrete the hormone called estrogen. The follicle with the maturing egg inside moves toward the surface of the ovary. At ovulation, the follicle and the ovarian surface open, allowing the tiny egg to float out. About this time, some women feel a twinge or cramp in the lower abdomen or back, usually accompanied by wet cervical fluid. The cervical fluid at this point is sometimes bloody.
After ovulation, if no pregnancy occurs, the released egg is swept into the funnel-shaped end of one of the fallopian tubes and begins its several-day journey to the uterus, moved along by wavelike contractions of the muscles in the tube. If the egg is not fertilized, it disintegrates or flows out with the vaginal secretions, usually unnoticed before menstruation.
Player 2: The Cervix
The kind of mucus or fluid produced by your cervix changes throughout the cycle in response to hormones. Although there are general patterns of fluid secretion, you can follow your own cycle to find a pattern.
As ovulation approaches under the influence of estrogen, the fluid changes to form longer, aligned strands that look like ferns and can guide sperm into the uterus. Thus, the fluid is a kind of gatekeeper for the uterus. Around ovulation, it is slick and thick enough to coat the vagina and protect sperm from the vagina’s acid secretions. After ovulation, as progesterone counteracts estrogen, cervical fluid thickens, and your vagina gradually becomes drier.
Players 3 and 4: The Endometrium and Uterus
Estrogen, made by the maturing follicle, cause the glands of the uterine lining to grow and thicken, and increases the blood supply to these glands. This thickening of the uterine lining is called the proliferative phase of the menstrual cycle, and it can vary in length from six to twenty days. Progesterone, made by the ruptured follicle after the egg is released, stimulates the glands in the endometrium to begin secreting embryo-nourishing substances. This is termed the secretory phase of the cycle. A fertilized egg can implant only in a secretory phase, not a proliferative one.
If conception has not occurred, the post-ovulation follicle will produce estrogen and progesterone for about twelve days, with the amount lessening in the last few days. As the estrogen and progesterone levels drop, the tiny arteries and veins in the uterus close off. The lining is no longer nourished and is shed. This is menstruation: the menstrual period or flow.
Player 5: Menstrual Fluid
During menstruation, most of the lining of the uterus is shed, but the bottom third remains to form a new lining. Then, as a new follicle starts growing and secreting estrogen, the uterine lining grows, and the cycle begins again.
During menstruation, it is not just blood that sometimes flows out of your vagina. In addition to blood, your menstrual fluid contains cervical fluid, vaginal secretions, cells, and endometrial tissue. This mixed content is not obvious, since the blood colors the fluid red or brown.
Women’s menstrual cycles vary widely. Many women’s cycles range from twenty to thirty-six days. While some women’s periods do occur exactly every month, other women have cycles that are longer or shorter. Some women have regular cycles (bleeding every twenty-eight to forty days), while other women have alternating long and short cycles. There are spontaneous small changes, and there can be major changes when a woman is under a great deal of stress or loses a significant amount of her body fat.
The number of days we bleed also varies. Many women’s periods last between two and eight days, with four to six days being the average. The flow stops and starts, though this may not always be evident. A usual discharge for a menstrual period is about four to six tablespoons, or two to three ounces, which is surprising, as it often looks like more.