ductus deferens

The ductus deferens, or vas deferens, is the thick-walled tube in the male reproductive system that transports sperm cells from the epididymis, where they are stored before ejaculation. An ampulla, which serves as a reservoir, is found at the end of each ductus deferens. The epididymides produce two ductus deferentes, which are identical in structure and function.

The ductus deferens channel is slightly larger than the ductus epididymidis, the tube found within the epididymis gland from which it originates. Mucous membranes line the inside wall. They are moist and folded. Three layers of circular and longitudinal muscle fibers surround the mucous membrane. Sperm and fluids can be transported through the ducts when these fibers contract. In the lower region of the scrotal sac, the pouch of thin skin covering the testes and epididymides, the ductus deferens begins at the tail of the epididymis. It extends into the pelvis. As it ascends to the level of the bladder, the ductus deferens is surrounded by arteries, veins (pampiniform plexus), and nerve fibers, and it is covered by connective tissue. (These complex tubular structures, collectively known as the spermatic cord, also support the testes.) At the bladder level, the ducts separate from their connective tissue sheaths and travel back over the top of the bladder; the two ducts turn downward at the rear of the bladder, and their channels enlarge to form the two ampullae attached to the outsides of the bladder.

Semen is stored in the ampullae, which produce secretions for it. Ergothioneine, a compound that reduces chemical compounds, and fructose, a sugar and nutrient, are found in the yellow secretions of the ampullae. The sperm are moistened by both secretions. Several folds and meshlike partitions are present in the interior of the ampullae. In the sperm canal, the walls of the ampulla are thinner, and the channel is usually larger. Its size varies with different animal species; in horses, the ampullae are relatively large, whereas in people, they are only about twice the size of the ductus deferentes. The ejaculatory ducts are formed when the seminal vesicles join the ampullae. Refer to ejaculation as well.