The testes are two organs within the scrotum, just below the penis. Their main function is to produce sperm and the male hormone testosterone.
Sperm produced in the testes is carried up into the body in two tubes called the "vas deferens" (one on the left and one on the right side of the body) to be mixed with other fluids and become part of the semen pushed out of the penis during ejaculation.
A vasectomy is a highly effective form of birth control that prevents sperm from becoming part of the semen by interrupting its flow up from the testes through the vas deferens.
Vasectomy is performed under local anesthetic in a procedure that typically takes less than an hour:
Vasectomy surgery involves numbing the area near the scrotum with local anesthesia, pulling a segment of each vas deferens outside the body through tiny incisions or punctures in the scrotum, cutting each tube and then sealing it, either by tying it off, sewing it shut or cauterizing it with heat. Each of the vas deferens is then tucked back into the body to heal.
Note that because sperm make up only a tiny amount of seminal fluid by volume, men do not ejaculate noticeably less after having a vasectomy.
After a vasectomy, sperm may continue to appear in semen for up to three months and/or twenty ejaculations. It is therefore important that three months following surgery, patients confirm two negative (zero-sperm) semen samples before discontinuing alternative birth control methods.