Vas deferens

Overview
The vas deferens (plural: vasa deferentia), also called ductus deferens, (Latin: "carrying-away vessel") is part of the male anatomy of some species, including humans.

Structure
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 (in humans).

They are part of the spermatic cords.

Function in ejaculation
During ejaculation the smooth muscle in the walls of the ductus deferens or vas deferens contracts reflexively, thus propelling the sperm forward. This is also known as peristalsis. The sperm is transferred from the vas deferens into the urethra, collecting secretions from the male accessory sex glands such as the seminal vesicles, prostate gland and the bulbourethral glands, which form the bulk of semen.

Significance in contraception
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.

Investigational attempts for male contraception have focused on the vas with the use of the intra vas device and reversible inhibition of sperm under guidance (RISUG).

Blood supply
The vas deferens is supplied by an accompanying artery (artery of vas deferens). This artery normally arises from the superior vesical artery, itself a branch of the internal iliac artery.