Also known as the vas deferens, the ductus deferens is a portion of the male anatomy that carries sperm from the epididymis to the ejaculatory duct. There are two vasa deferentia, one for each epididymis, where sperm cells are temporarily stored outside the testicles where they are produced. In the ejaculatory duct, the sperm cells are mixed with enzymes and other ejaculatory fluid to form semen, which then exits the body through the urethra. The ductus deferens in the human male is about 11.8 inches (30 cm) long, and the smooth muscle surrounding it aids in transporting sperm down its length.
A deferentectomy, also known as a vasectomy, involves cutting the ductus deferens so that sperm cannot be carried from the epididymis into the ejaculatory duct. Because semen consists mostly of secretions created in the seminal vesicles, prostate and bulbourethral glands, a man can still ejaculate, but the absence of sperm provides a method of permanent birth control. In some cases, a vasectomy can be reversed, but the results of the reversal procedure are not guaranteed. A vasectomy does not affect sexual function or pleasure and is a safe and very effective form of birth control.
Another means of performing a vasectomy involves blocking the ductus deferens rather than cutting it. This method is generally just as effective as a traditional vasectomy. With any type of vasectomy procedure, another form of birth control must be used for at least three months to allow the seminal vesicles to empty completely of motile sperm.
In some cases, genetic factors cause the ductus deferens to develop abnormally, a condition referred to as congenital bilateral absence of the vas deferens (CBAVD). Men with this condition are infertile because the sperm produced in the testes cannot be transported to the ejaculatory duct. The genetic abnormalities that result in CBAVD have been linked to cystic fibrosis. Not all men with abnormal development of the ductus deferens manifest cystic fibrosis, but some do have additional issues such as digestive problems or respiratory issues, which are symptoms related to cystic fibrosis.
Cystic fibrosis affects the consistency of mucus throughout the body and is a systemic disorder. Nearly all men suffering from this disease also suffer from CBAVD and are infertile as a result. They do, however, tend to produce sperm in a normal manner. Men with cystic fibrosis and CBAVD generally must pursue alternate fertilization methods with their partners in order to father children.