[3]: 1297  It is continuous proximally with the tail of the epididymis,[3]: 1296  and exhibits a tortuous, convoluted initial/proximal section (which measures 2–3 cm in length).

At the deep inguinal ring, the vas deferens diverges from the testicular vessels to pass medially to reach the base of the prostate posteriorly.

[3]: 1297 During ejaculation, the smooth muscle in the walls of the vas deferens contracts reflexively, thus propelling the sperm forward.

[11] The epithelial sodium channel ENaC is strongly expressed in smooth muscle cells of the vas deferens.

[1] It has been suggested that ENaC functions as a mechanosensor in vascular smooth muscle cells that initiate pressure‐induced constriction known as the "myogenic response".

Thus, these channels are involved concurrently in the regulation of fluid and electrolyte balance in the lumen of the vas deferens.

A modern variation, vas-occlusive contraception, involves injecting an obstructive material into the ductus to block the flow of sperm.

In cartilaginous fish and amphibians, sperm are carried through the archinephric duct, which also partially helps to transport urine from the kidneys.

In teleosts, there is a distinct sperm duct, separate from the ureters, and often called the vas deferens, although probably not truly homologous with that in humans.

[21] In amniotes (mammals, birds, and reptiles), the archinephric duct has become a true vas deferens, and is used only for conducting sperm, never urine.