Sperm is made in the male testes through a process called spermatogenesis, which develops immature cells called spermatogonia into fully mature sperm cells called spermatozoa. This begins in the seminiferous tubules, where the spermatogonia undergo division in a process called mitosis. In the last stage of maturation, called spermiogenesis, the sperm cell elongates, grows a tail and rotates so that its tail faces inside the tube.
In the process of maturation, the head of the sperm develops a cap called the acrosome, which helps it break down the wall of the female egg during fertilization. The tail propels the sperm using an undulating motion. Once the sperm is fully mature, it travels through the seminiferous tubules and is stored in the epididymis of the testes until it leaves the body during ejaculation.
From the beginning of the process until the end, it takes about 70 days to make sperm. Boys begin to produce sperm when they go through puberty. Sperm is continually produced in males, unlike women who ovulate only once per month. In human males with normal reproductive systems, every ejaculation contains approximately 200 to 300 million sperm. In addition to sperm, ejaculated semen contains a number of other liquids, including secretions from the seminal vesicles, Cowper's gland and prostate gland.