Although most women today probably feel they know as much as they’ll ever need to about their female sexual or reproductive parts, let me explain how they are classified in medical terminology. The vagina is the passageway to the internal organs; the ovaries offer a storage place for the eggs; the tubes provide a site for fertilization and passageway for transportation of the fertilized egg or blastocyst; the uterus is the site for implantation of the developing fetus.
Externally, you have the vulva, the area between your upper thighs, which includes the mons pubis, labia majora, labia minora, clitoris, hymen, urethral opening and various glandular structures.
The mons pubis is a fat-filled cushion, covered by curly pubic hair, which is n a triangular-shaped pattern in the female. The labia majora are two rounded folds of fat, covered in tissue, similar to the scrotum in the male. In young girls, the labia majora lie close together, whereas in women who have had children the labia may gap. Following puberty the labia are covered with hair, which extends onto the inner things.
The labia minora, reddish in color, vary greatly in size. After childbirth they can project out. Their thin folds of tissue enfold never endings, and their muscles can make them erectile.
The clitoris is the equivalent to the male penis, a small erectile body that rarely exceeds 2 centimeters in length even in a state of erection. The clitoris is extremely sensitive to touch, being one of the principal female erogenous zones.
The urethra is the opening to the bladder. Close by, just under it, is the vaginal opening, which varies in size and shape in different women. A tubular or hollow muscular structure between the bladder and rectum, the vagina is the major female organ of copulation. It can vary considerably in length, though it is usually about 10 centimeters long. In childbirth, however, it will distend markedly. The lower portion of the cervix, which is the entrance to the uterus, or womb, projects into the top of the vagina.
The cervix and uterus
The portion of the cervix visible from the vagina has an opening in its center known as the external os. Before childbirth it is small and oval, but it changes in shape after your first child. The other end of the cervix, which opens into the lower portion of the uterus, has an opening known as the internal os. The cervix is only a few centimeters in length. The cervix is composed mainly of smooth muscle, collagen tissue becomes flexible so that it will separate and soften. Normally the percentage of muscle content is low—around 10 percent. However, in a woman with an incompetent cervix is appreciably greater. The glands in the canal, or passage, in the cervix secrete a mucus that provides a protective plug during pregnancy and that when discharged at the onset of labor is called “show”. The isthmus between the body of the uterus and the cervix stretches during late pregnancy and labor, forming the lower segment or lower part of the uterus through which C-sections are done if needed.
The uterus is a muscular organ, the shape of which has often been likened to an inverted pear. It has a cavity lined with tissue, known as the endometrium, which in turn nourishes the fetus in pregnancy under the influence of progesterone. This endometrium is a thick, pink velvetlike membrane, varying in depth from 0.5 to 5 millimeters, lined with blood vessels. The endometrial cells undergo many changes that, as we saw earlier in this chapter, can be recognized at each stage by the pathologist during menstrual cycle.
The fallopian tubes come out of cornua, or angles, at each side at the top of the uterus. They vary in length from 6 to 10 centimeters, and will shrink markedly after the menopause. They also vary in thickness from 2 to 3 millimeters to 5 to 8 millimeters in diameter. Like the endometrium, the tubes are lined with a mucus membrane. This lining is composed though of only a single layer of cells, and it also undergoes changes throughout the cycle, changes that are important for a woman’ fertility. For example, if the lining has been damaged, the tube may not be able to support fertilization satisfactorily and may be a cause of sterility.
Each tube is divided into four parts: the tissue that runs through the wall of the uterus and then up into the tube (the internal portion), the part that runs next to the uterine wall (the isthmical portion),. The final part, at the end of the tube, extends in fingerlike structures called fimbria to the surface of the ovary, ready to surround the egg like the tentacles of an octopus, as it is slowly expelled from the surface of the ovary at the time of ovulation. The egg, once released, is transported along the tube by these hairlike cells helped by contractions of the walls of the tube.
The ovaries are almond-shaped organs that develop and produce eggs. They also secrete their own share of hormones. The ovaries vary in size from 2.5 to 5 centimeters in length and shrink after menopause. They are located in the upper part of the pelvis, on its back wall, lying between two large blood vessels and behind the fallopian tubes.
The endometrium (lining of the uterine cavity) and hormonal chage
There are three main changes to the endometrial cycle each month which are very important in the reproductive chain:
1. Menstrual phase
2. Follicular or proliferative phase
3. Secretory or luteal phase
Following a menstrual period ( menstrual phase), the endometrium is thin, since te blood-vessel lining has been completely shed. It gradually builds up and becomes thicker (follicular or proliferative phase) until it reaches the stage when it is thick and nourishing (secretory or luteal phase) again. These changes are brought about by the timed release of hormones during the menstrual cycle.
At the time of menstruation, for example, the midbrain produces gonadotropins-releasing hormones that travel down to the pituitary gland lower in the brain. In turn, gonadotropins are then released; at first, the main hormones is FSH( follicle stimulating hormone). The FSH travels through the blood stream to the ovary, where it cause an egg (or follicle) to ripen. The very act of ripening cause the egg to produce the hormone estrogen, which in turn triggers the endometrial lining to begin developing once again (proliferative phase).
At midcycle, around day 14, another gonadotropin is secreted by the pituitary gland in the brain called LH (luteinizing hormone), and this cause the egg to leave the ovary (ovulation). From the onset of menstrual to ovulation lasts about 14 days, but in reality may vary between 8 to 20 days.the second part of the cycle is more exact: from ovulation it takes exactly 14 days before the onset of your next period, unless you become pregnant. So you always ovulate 14 days before your next period, not necessarily 14 days from the start of your last period.
The moment of release of egg is not a sudden act, as many women believe. In fact, it takes place quite slowly over a period of two to three minutes. The expulsion of the egg may also be accompanied by a little spillage of fluid from the now empty structure (the follicle). If the fluid spill into the pelvic cavity, it may be accompanied by a little pain or cramping. This is the mittelschmerz—a midcycle sensation of lower abdominal pain—lasting only a few hours. Some mucus or blood may also be released into the vagina (ovulation casade). Both are not only common, but good signs of ovulation.
The egg is then picked up by a fallopian tube. The pituitary gland continues to secrete the gonadotropin LH, which also cause the follicle that expelled the egg to produce progesterone (as well as estrogen). The follicle is now called the corpus luteum. LH is secreted for 14 days, at which time the corpus luteum (which with conception would persist to support the early pregnancy) degenerates and a new cycle start over with the onset of the menstrual phase.
The production of progesterone during the luteal phase is very important in maintaining a pregnancy. When the egg is fertilized, LH will continue to be secreted, and the corpus luteum will not degenerate but continue to produce progesterone that makes the endometrium secretory, building up nutrients for the early fertilized egg.
When a pregnancy occurs, the message to the corpus luteum not to die after 14days, and the endometrial membrane to continue their secretion, comes from a pregnancy hormone, HCG, or human chorionic gonadotropin, which has in itself been produced by the fertilized egg. So, it is the fertilized egg that gives the signal to keep producing progesterone, to keep producing progesterone, to keep itself alive, and well nourished. HCG is another very important hormone of pregnancy as it stops the corpus luteum from degenerating for at least the first 8 to 9 weeks, until the placenta has developed and is ready to take over.
