<P> They are part of the spermatic cords . </P> <P> The vas deferens is supplied by an accompanying artery (artery of vas deferens). This artery normally arises from the superior (sometimes inferior) vesical artery, a branch of the internal iliac artery . </P> <P> During ejaculation, the smooth muscle in the walls of the 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 . </P> <P> The procedure of deferentectomy, also known as a vasectomy, is a method of contraception in which the vasa deferentia are permanently cut, though in some cases it can be reversed . A modern variation, which is also 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 . </P>

When are spermatozoa transported from the vas deferens to the abdominal urethra