The sperm ducts (or ductus deferens) are a complex set of structures of various kinds whose main functions are two fold: to allow the transit of sperm from the testicles to the outside of the body and allow the maturation of the sperm cells themselves.

What are the sperm ducts?

The sperm ducts have a network of structures that belong to the genitourinary and reproductive systems.

The sperm ducts begin within each testicle with the straight seminiferous tubules, small channels responsible for the production of sperm (spermatogenesis) and its excretion. The tubules are intertwined to form the rete testis (testicular network). From the testicular network of each testicle begin the efferent ducts that reach the epididymis (small elongated body on the top-rear edge of the testicle), and the final tract of the sperm ducts is located between the efferent ducts of rete testis and the vas deferens (main transport channel for semen).

The tracts or spermatic cords represent the universe of the vas deferens and blood vessels and nerves that are flanked in its course. The ejaculatory ducts, which are essential for the transport of sperm, extend through the prostate gland and are included in the prostatic urethra.

Finally, the urethra, which allows the expulsion of sperm outside the male body, is the last part of the sperm ducts (excluding the initial portion).

The tissue that lines the inside wall of the sperm ducts is a moist layer of mucous membrane. The mucous membrane is surrounded by three layers of circular and longitudinal muscle fibres, which facilitate muscle contractions of the ducts. Thus, allowing the sperm and fluids to be transported.

Each of the sperm ducts receives blood supply from an artery that is typically derived from the superior vesicle artery with venous drainage to the pelvic venous plexus. The lymphatic drainage of the sperm ducts is to the external and internal iliac nodes. The innervation or nerve supply of the sperm ducts is mainly from sympathetic nerves that belong to the pelvic plexus.

What function do the sperm ducts serve?

There are two main functions of the sperm ducts: to allow the transit of sperm from the testicles to the outside of the body and to facilitate the maturation of the sperm cells themselves.

The sperm that passes through the sperm ducts is not yet motile and therefore it must be transported through peristalsis with the help of the muscle tissue that lines the walls of the sperm ducts. When the sperm reaches the far end of the sperm ducts it can be stored in the ampulla (cavity or a dilated end of a duct) to await ejaculation. Old and non-viable sperm are absorbed in the epithelial lining of the ampulla and later broken down by the body.

Moreover, the different structures that form the sperm ducts also have the ability to change the composition of the substances secreted within them through a dual mechanism (secretory and absorbing).

The functionality of the sperm ducts is regulated through the male hormones.