The vas deferens is the duct which transports the spermatozoa from the epidiymis to the glands at the base of the bladder. These glands together form the seminal plasma. The vas is about 30 cm long and is a muscular structure which during ejaculation propels the semen - and hence the spermatozoa - through the urethra  to the outside.

Male sterilization is carried out by dividing both vas. After vasectomy sexual, spermatogenesis and hormone production remain normal - after vasectomy  the vas can still store spermatozoa and unprotected intercourse should not be considered safe until two consecutive semen samples show absence of spermatozoa. Vasectomy is not 100% effective.

Reversal of vasectomy is possible but its effectiveness may diminish with time due the presence of antisperm antibodies.