Vas deferens, a component of the male reproductive system, is a thick walled tube that conveys mature sperm from the epididymis to the ejaculatory duct. It is about 18 inches long, arising from the lower end of the epididymis. It then passes through the inguinal canal to enter the pelvic cavity and emerges from the deep inguinal ring lateral to the inferior epigastric artery.
After emerging through the deep inguinal ring, it passes downward and backward on the lateral wall of the pelvis and crosses the ureter near the ischial spine. The terminal part of the vas deferens runs on the posterior surface of the bladder where it is dilated to form the ampulla of vas deferens. The inferior end of the ampulla narrows down and joins the duct of seminal vesicle to form the ejaculatory duct.