Vas Deferens

The vas deferens (ductus deferens) is the thick-walled muscular tube, about 30-45 cm long, that carries sperm from the epididymis up through the groin (in the spermatic cord), over the pelvic brim and behind the bladder, where it joins the seminal vesicle duct to form the ejaculatory duct. Its powerful peristaltic contractions propel sperm during ejaculation. It is the structure divided in a vasectomy.

Key facts

Its wall has one of the thickest muscle-to-lumen ratios of any tube in the body, built for forceful propulsion.
It can be felt through the scrotal skin as a firm, cord-like structure — the basis of the no-scalpel vasectomy approach.
Behind the bladder it widens into an ampulla where sperm can be stored.
Congenital absence of both vasa occurs in some men with cystic fibrosis gene variants and causes infertility with otherwise normal health.

What can go wrong

The vas is central to male sterilisation: vasectomy divides it through a small scrotal approach, blocking sperm while leaving hormones and fluid production unchanged. It can be obstructed by infection scarring or injured during hernia surgery, contributing to infertility. Reversal operations rejoin it, with success depending largely on time since vasectomy and surgical findings.

Related conditions

Related procedures & tests

Frequently asked questions

Does vasectomy affect testosterone or erections?

No. The testes keep producing testosterone into the bloodstream and the glands keep making seminal fluid; only the sperm's route out is blocked, and sperm make up a tiny fraction of the ejaculate volume.

Can the vas deferens be absent?

Yes — some men are born without one or both, sometimes linked to cystic fibrosis gene variants; it is a recognised cause of absent sperm in the ejaculate.

Educational information only. This atlas explains normal anatomy and describes conditions in general terms; it is not medical advice and does not replace assessment by a qualified clinician. If you have symptoms that worry you, seek medical care.