What is Spermatogenesis in human biology?
The male sex cells, or sperm, are produced in the oval-shaped testes, the primary sex organs of the male reproductive system, in a process known as spermatogenesis Sperm are produced through meiosis in the germ cells lying in seminiferous tubules in the testes. In this process, spermatogonia, or diploid germ cells, undergo many successive mitotic divisions to form large numbers (about 3 million in 1 day) of primary spermatocytes. These cells enter the first meiotic division to become haploid secondary spermatocytes.
The second meiotic division produces four spermatids for each primary spermatocyte. Spermatids start out as rounded cells, but soon develop into tadpole-shaped sperm. Specialized cells called Sertoli cells provide nutrients for the developing spermatids.
A sperm is a highly specialized cell consisting mostly of a head containing a nucleus with a haploid genome. It also bears a long flagellum for movement, and a packet of mitochondria just behind the head, providing ATP energy to the flagellum. At the tip is the acrosome, a cap structure containing enzymes that enable the sperm to penetrate the egg.
Once fully developed, sperm are released into the cavity of the coiled mass of seminiferous tubules, which occupy most of the space in the testes. The space between the tubules contains interstitial cells, which secrete the male hormone testosterone. Testosterone is responsible for secondary sexual characteristics such as beard growth, deep voice, and strong muscles.
Human testes are located in the scrotum, a sac that hangs outside the body cavity. This allows the temperature of the testes to remain at about 4°C cooler than the rest of the body, an optimal temperature for sperm development. Many scientists believe that tight clothing may press the scrotum to the skin of the abdomen, increasing the temperature and decreasing sperm count.