Throughout their lives, men produce sperm that can impregnate a woman. Sperm production begins at puberty and continues until death.

Sperm are produced in the testes. They go through a number of stages over a period of about two and a half months before they are ready to fertilize an egg. They are then stored in the seminal vesicles.

When a man ejaculates, sperm from the seminal vesicles are mixed with fluid from the prostate and the glands of the male reproductive organs. This is known as semen. The semen from a single ejaculation usually contains between 20 million and 200 million sperm cells. Sperm can live 72 to 120 hours in a woman’s genital tract, but only a few seconds outside it.