Running with obstacles

Running with obstacles

In humans, fertilization occurs inside the body: it is necessary to introduce sperm into the female genital organs, which is carried out during sexual intercourse, or copulation. Copulation begins with the erection of the male penis and continues with its insertion into the vagina and ejaculation of semen.

Sperm penetrate the uterus and travel up the fallopian tube, where fertilization occurs. This path is a steeplechase and a real test of endurance. Hundreds of millions of sperm die in the cervix from the caustic secretion of its mucous membrane. Mucus acts as a selective filter: only 1% of sperm reaches the uterine cavity. Many more die inside the uterus, and only a few hundred manage to ascend the fallopian tube to meet the egg.

If fertilization occurs normally, only one of them will be able to break through the membrane of the egg and fertilize it. During this 30-minute process, sperm are attracted to a chemical released by the egg. Those that linger in the female genital canals are capable of fertilization for another one or two days.

As a result of fertilization, a zygote is formed - the first cell of a new organism. The process of fertilization consists of two well-differentiated periods: fertilization, when the sperm breaks through the membrane of the egg, enters the head and body, loses the tail and forms a new membrane that prevents fertilization by another sperm. Then the sperm nucleus merges with the egg nucleus and a cell of 46 chromosomes is formed, which gives rise to the development of the embryo.

Thus, the path of the sperm to the egg is a real obstacle race, where out of millions of participants only one becomes the winner.