The vas deferens, also called ductus deferens, (Latin: "carrying-away vessel") is part of the male anatomy of some species, including humans. There are two such ducts; they are muscular tubes (surrounded by smooth muscle) connecting the left and right epididymis to the ejaculatory ducts in order to move sperm. Each tube is about 30 centimeters long.

During ejaculation the smooth muscle in the wall of the vas deferens contracts reflexively, thus propelling the sperm forward. The sperm are transferred from the ductus deferens into the urethra, collecting fluids from the male accessory sex glands en route. Hence the hoary joke: "Between men and women, there is a vas deferens."

The procedure of deferentectomy, popularly known as a vasectomy, is a method of contraception in which the vasa deferentia (Latin plural) are permanently cut, though in some cases it can be reversed. A modern variation, which is also popularly known as a vasectomy even though it does not include cutting the vas, involves injecting an obstructive material into the ductus to block the flow of sperm.

Cystic Fibrosis in males causes the blocking of vas deferens rendering them infertile this affects 95% of male CF sufferers.

See also

• Intra vas device

Male reproductive system

Samenleiter | Vaso deferente | Canal déférent | Sėklinis latakas | Zaadleider | Semenovod | Siemenjohtimet | Nasieniowód | Sädesledare | 输精管 | צינור הזרע