Gender Medicine by Marek Glezerman

Author:Marek Glezerman [GLEZERMAN, MAREK]
Language: eng
Format: epub
Tags: SCI000000; MED000000
ISBN: 9781468313499
Publisher: The Overlook Press
Published: 2016-06-21T04:00:00+00:00

THE REPRODUCTIVE PROCESS

It’s incredible that a simple merger of two cells—sperm and egg—can, within a period of nine months, result in a new human body containing ten trillion cells. Moreover, all the cells in our body carry the same, original genetic load, but combine to produce numerous complex systems. This miracle is the result of the reproductive process.

In fertile women, thousands of follicles grow in the ovaries each month. One (or sometimes more) of these follicles bursts and releases an egg into the fallopian tube which leads to the uterus in a process called ovulation (see Fig. 1). The egg waits in this tube, ready to be fertilized. If the egg is not fertilized within a short period of time—12 to 24 hours—the window of opportunity closes and the egg is no longer viable. Because most couples do not have daily sex, it would require a great coincidence for sperm to be present in the fallopian tubes at the required time. Hence, a compensatory mechanism emerged in nature. Sperm cells evolved greater survival abilities and can remain in the female genital tract for over a week after intercourse awaiting an egg. Thus a woman can in effect maintain a reservoir of sperm in her cervix for up to a week. This mechanism also explains why there are no “safe days” for preventing pregnancy prior to ovulation.

The tadpole-like sperm cell is unlike any other cell in the body. It consists of a head containing genetic material, a neck comprising mainly energy-producing organelles, and a tail that translates this energy into the movements typical of sperm cells. The mission of sperm cells is to exit the male body into that of the female, to travel against the current of mucus flowing out of the cervix, to cross countless barriers and to arrive at the coveted goal, the single egg in the fallopian tube. Of the hundreds of millions of sperm cells embarking on this journey in a single ejaculation, in the best of cases only one sperm cell will manage to fertilize the egg—the victory of one out of hundreds of millions. From this perspective, each one of us represents a winner.

Eventually, a group of sperm cells will encounter the egg that has just been released from the ovary. The egg proceeds slowly toward the uterus, moved by wavelike contractions of the fallopian tube, wrapped in designated cells known as granulosa cells. The encounter between the egg, the body’s largest cell, and the sperm cells, the smallest, is dramatic. Like enthusiastic fans attempting to push toward the entrance of a stadium, the sperm cells proceed tirelessly in an attempt to penetrate the cell layers surrounding the egg. But this is not merely a mechanical process of active sperm cells and a passive egg. It is a complex cooperative process involving catalyst substances called enzymes. This cooperative action leads to the creation of a channel through which the sperm cell travels to the egg, and after one sperm cell succeeds, it blocks other sperm cells from continuing to dig through the surrounding cellular envelope.

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