Sperm production and transport

Male reproductive anatomy

The male reproductive tract consists of the testes, which produce sperm, and a series of ducts and tubes allowing the sperm and seminal plasma to be secreted (see Fig. 1.1). Testicular sperm drain into the epididymis which is a single convoluted tubule opening into the vas deferens. The epididymis is divided into three regions, the caput, corpus and caudum. Sperm concentration and maturative changes occur in the caput and corpus regions and are regulated by the concentrations of hormones and proteins within the epididymis. The cauda acts as a sperm reservoir where sperm may be stored for several weeks before being released into the vas deferens. The vas is approximately 25 cm long and passes into the peritoneal cavity via the inguinal canal before opening into the urethra. Secretions from the accessory glands, the seminal vesicles and prostate, drain into the urethra to form the bulk of the semen or seminal plasma. The bulbourethral glands produce a small amount of seminal fluid.

Anatomy of the testis

The testes are paired organs consisting of an outer capsule, the tunica albuginea, the seminiferous tubules, which form sperm, and the interstitial tissue (see Fig. 1.2). The seminiferous tubules, which occupy most of the volume of the testis, are contained in lobules (of which there are approximately 300), each lobule containing between one and four tubules. The tubules are composed of germ cells and Sertoli cells. The sperm produced in the seminiferous tubules pass into the ductus efferentes and rete testis before reaching the epididymis. The interstitial tissue fills the spaces between the seminiferous tubules and contains the Leydig cells.