How Spermatogenesis Works

Fertility & Conception
Key Points

  • Men produce sperm every day.
  • It takes 74 days for one sperm cell to fully mature.
  • Sperm has 3 components: nucleus, acrosome and flagellum.

What is Spermatogenesis?

Men start producing sperm in puberty and continue throughout most of their lives. The process of producing fully functional sperm cells is called spermatogenesis. Spermatogenesis takes place within several structures of the male reproductive system, including the seminiferous tubules, which are an intricate system of tubules in the testes. The seminiferous tubules can sometimes produce over 100 million sperm per day!

The location of testis is specifically important as the process of spermatogenesis which requires a lower temperature to produce viable sperm, specifically 1° to 8 °C lower than normal body temperature of 37 °C.

Sperm Anatomy

Sperm has three basic components:

  • The nucleus which contains the haploid genome.
  • The acrosome which is a structure that forms a cap over most of the nucleus of the sperm cell. The main job of the acrosome is to penetrate the outer layers of the egg so that the sperm can get inside..
  • The flagellum which is a long tail, used for movement.

Sperm Production

The germ cells that are found in the testes are called spermatogonia. Every day, somewhere around 25 million spermatogonia enter meiosis and become primary spermatocytes. After the first meiotic division, the cells double in number and are called secondary spermatocytes. Once the second meiotic division is completed but before the haploid cells have had a chance to differentiate into actual sperm, the cells are called spermatids. These spermatids now have the correct number of chromosomes to be functional gametes, but they don't have the physical characteristics of sperm that allow them to swim to the ovum and fertilize it.

The entire process of spermatogenesis is estimated to take 74 days. Testes produce 200 to 300 million spermatozoa daily. However, only about half or 100 million of these become viable sperm.

The Small Book of Fertility Hormones