Читать книгу You: Having a Baby: The Owner’s Manual to a Happy and Healthy Pregnancy - Michael Roizen F. - Страница 29

On the other side of the equation, of course, we have those little swimming sperm. As with a woman’s eggs, each sperm contains a single copy of each gene in the human genome. Unlike women, men don’t have a preset number of their reproductive players. In fact, a man produces more sperm in each ejaculation than the total number of eggs that a woman is endowed with for life. (Evolutionarily, a man can continue reproducing for the majority of his adult life, maximizing the chance of passing on his genes. A woman’s reproductive life is limited to the younger years of her life because of the physical strain of pregnancy, childbirth, breast-feeding, and child rearing.)

A man’s sperm, which is carried in semen that’s made by glands such as the prostate, is stored in a duct called the vas deferens. When a man ejaculates, the sperm-carrying semen fires out through the urethra in a seek-and-conquer mission. It may seem that all these millions of sperm are racing one another to the finish. But just like a Tour de France cycling team, the sperm have different roles. Some are deemed the leaders of the pack, trying to be the first to cross the line. Others are designed to assist, specifically by blocking other men’s sperm from making it to the finish line. Competitive little game going on in there, eh? The goal of pregnancy, of course, is for a sperm to find an egg during a precise window of opportunity and fertilize it.