Male Reproductive System

This page outlines the basic anatomy and function of the male reproductive system. Separate pages describe the female reproductive system and characteristics of the reproductive system common to both males and females.

1. Anatomy of the male reproductive system:
   1. The external genitalia of the male consist of the penis and scrotum.
   2. The urethra is the common passageway for semen and urine.
   3. The testes are the male gonads. Sperm travel from the testes to the urethra via the ductus deferens.
   4. Accessory glands contribute secretions to the sperm as they travel along the pathway from the testes to the urethra. These glands include the prostate gland, the seminal vesicles, and the bulbourethral glands. Their secretions constitute most of the volume of the semen that the male eventually ejaculates.
2. Sperm production takes place within the testes:
   1. The internal structure of the testes consists of coiled masses of seminiferous tubules. Germ cells (spermatogonia) embedded in the walls of the tubules give rise to developing sperm by the process of meiosis, becoming primary spermatocytes after the first meiotic division and secondary spermatocytes after the second division. Each secondary spermatocyte then undergoes a gradual transformation into mobile spermatids, losing most of its cytosol and developing an elongated flagellum.
   2. Spermatid development is regulated and supported by Sertoli cells that are also embedded in the walls of the seminiferous tubules. FSH from the anterior pituitary stimulates the Sertoli cells to produce a variety of factors required for normal spermatogenesis. These include:
      1. Androgen binding protein, which traps testosterone in the fluid surrounding the developing spermatids.
      2. Inhibin, which selectively inhibits FSH release by the anterior pituitary.
3. The other major function of the testes is production of testosterone. This is handled by Leydig cells found in the interstitialspaces (outside the seminiferous tubules). Leydig cells are stimulated to produce testosterone by LH from the anterior pituitary. Testerone, in turn, travels back to the anterior pituitary to suppress release of LH.

See also: