THERE ARE TWO of us, and we hang by ligaments on either side of your pelvis. We are whitish, generally almond-shaped, 1 1/4 inches long. Together we weigh barely a quarter of an ounce.
Despite our uninteresting appearance and insignificant size, my partner and I (I am your right ovary) are the most feminine components of your body. We play a dominant role in your life, to a great degree determining your moods, your sex drive, your general health. Indeed, it is my partner and I who transformed you into a woman in the first place.
Until you were about 12 years old - it might have been earlier or later - you were flat chested, tomboyish and sexually immature. Then, at a signal from your pituitary gland, we supplied magic-wand hormones that set off a re-sculpturing of your body. Your pelvis widened; fat pads appeared on your hips; breasts began to develop; pubic and other hair sprouted; and your overall sexual apparatus began to mature.
For the next 35-odd years, we would give you monthly reminders of our presence, participating in the regulation of your menstrual cycle with clockwork precision. When you have/had your first baby, we supply/d one of the two basic raw materials of human life: the egg. A few years from now, my partner and I will close up shop, and your fruitful years will come to an end.
When you were a small child, I was a minute affair. Yet even then my colleague and I contained about half a million microscopic egg cells, or ocicytes, and each of them contained all the thousands of factors representing your infants' contribution to the inheritance of babies that you yourself would later bear. During your fruitful years, we ovaries will produce only 400-odd mature eggs capable of being fertilized-approximately one every 28 days. Why, then, 500,000 egg cells? I do not know. It's probably just another example of nature's extravagance.
How is any particular egg cell chosen to develop into a full-grown, fertilizable egg? I wish I could tell you. I cannot; I can only give a rough picture of what happens.
Early in the menstrual cycle, the pituitary gland secretes minute squirts of follicle-stimulating hormone (FSH). It is difficult to conceive of the potency of this stuff. Less than a millionth of an ounce a day is quite sufficient to launch a dazzling chain of events.
Under the FSH prod, several of my dormant egg cells awaken. A fluid-filled follicle forms around each of these growing cells, and the resulting bubbles, expanding rapidly, start pushing their way toward my surface.
Only one bubble will make it (unless you are headed for a multiple birth involving no identical offspring). In about two weeks, it will appear as a blister about the size of a marble protruding from my surface - and representing one fourth of my volume. At this point, the pituitary secretes a spurt of a substance called luteinizing hormone, which causes the tissue-thin membrane covering the follicle to burst. The contents ooze out, and the ripe egg is swept along by a tidal wave of fluid. The egg drops gently into the funnel mouth of the Fallopian tube (see diagram) for transport to the womb, and for possible fertilization en route.