The Anatomy of the Vas Deferens

The vas deferens are an important part of male reproductive anatomy. These paired muscular tubes are also called the ductus deferens. They function to carry sperm from the epididymis to the urethra where it leaves the body during ejaculation.

It is the vas deferens which are ligated (severed or cut) during a vasectomy, a procedure for male surgical sterilization. It prevents sperm from leaving the body during intercourse and fertilizing an egg, leading to pregnancy.

Anatomy

The vas deferens are best described as a pair of hard, thick-walled, muscular tubes. These two tubes are identical and are each approximately 18 inches or 45 centimeters long. They are part of the spermatic cord which also consists of blood vessels and a network of nerve fibers surrounded by connective tissue.

The vas deferens begin at the epididymis, which is a place where sperm is stored after it is made in the testes. From the epididymis the vas deferens extend through the pelvic region to the level of the bladder. Here the two tubes branch off eventually forming two ampullae which attach to the left and right walls of the bladder. These ampullae are storage chambers for semen. The ampullae eventually join up with the ejaculatory ducts which connect them to the urethra.

The actual structure of the vas deferens has three layers. The outermost layer is made of connective tissue and called the adventitia. Beneath this layer is the muscular coat which consists of various layers of muscle fibers. The innermost layer is called the mucous coat which is lined with columnar epithelial cells.

Anatomical Variations

While rare, it is possible to be born without vas deferens—a condition which causes infertility. The congenital absence of the vas deferens can occur alone but is often associated with another genetic condition called cystic fibrosis. While males who are born without the vas deferens are typically infertile the condition does not affect their sex drive or ability to have sex. Some people with congenital absence of the vas deferens are able to father children with the assistance of reproductive technology.

Function

As previously mentioned the main function of the vas deferens is to carry sperm, in fact the term vas deferens actually means carrying-away duct in latin. Sperm is made in the testes and then transferred to the epididymis, a structure like a coiled tube nearby that serves to store sperm while it matures. When the penis become filled with blood and erect this prompts the sperm cells to move out of the epididymis and into the vas deferens.

The vas deferens propels the sperm forward by way of muscular contractions. When sperm reaches the ampullae it is joined by secretions from the seminal vesicle. From the ampullae, the seminal fluid is propelled through the ejaculatory ducts, past the prostate gland where a milky fluid is added to the mixture, and finally through the urethra where it exits the body.

Associated Conditions

The vas deferens is affected by various conditions, as well as being the target of vasectomy surgery.

Obstructive Azoospermia

Obstructive azoospermia is a condition where either the vas deferens, the epididymis, or the ejaculatory ducts are blocked or obstructed preventing sperm from traveling properly along its normal route to leave the body. Typical causes of obstruction may include congenital deformities (congenital absence of the vas deferens is actually a form of obstructive azoospermia), trauma, injuries, or complications from surgeries including hernia repair or vasectomy. Sometimes these obstructions can be surgically corrected to restore the proper flow of sperm and fertility.

Inflammation

Inflammation of the vas deferens is a rare condition sometimes referred to as vasitis. It often occurs after a vasectomy in which case it may cause no symptoms other than a palpable mass in the vas deferens. This mass may not necessitate any treatment but may need to be biopsied to confirm that it is benign.

While more rare, infections can also cause inflammation of the vas deferens. These rare infections are usually caused by the same types of bacteria that cause urinary tract infections and once diagnosed can typically be treated with antibiotics.

Vasectomy

A vasectomy is a common surgical procedure that involves cutting, burning or otherwise purposely occluding or impairing the function of the vas deferens as a means to render a man sterile. It is one of the most widely used forms of male contraception available. This procedure is often done in a healthcare provider's office or a surgical center under local anesthesia. It is often performed by a specialized healthcare provider called a urologist although other types of healthcare providers may be qualified to do the procedure as well.

Vasectomies result in infertility in more than 99% of men who undergo the procedure. Over 500,000 vasectomies are performed in the U.S. yearly. This makes it the fourth most common form of contraception. While vasectomies are intended to cause permanent sterilization, they can occasionally be reversed with surgery (vasovasostomy). They can also, on occasion, fail as it is actually possible for the vas deferens to reconnect (this is called recanalization).

While a vasectomy does not prevent the testes from producing new sperm, it prevents the sperm from mixing with seminal fluid and exiting the body. Instead, the sperm is reabsorbed. Following a vasectomy, semen must be tested periodically to make sure that no sperm is present or if there is sperm in the semen it is not motile. Until a positive confirmation of sterility comes back from the laboratory back up contraception must be used. This usually takes at least three months.

Risks of a vasectomy include a negative reaction to the anesthetic medication used, bleeding, infection at the site of the incision (or puncture), recanalization, hematoma and sperm granuloma. It is also possible to develop chronic pain, a condition called post-vasectomy pain syndrome. It is normal to have some pain for a few days following a vasectomy and ice packs are recommended to help with any pain or swelling. Follow your healthcare provider's instructions exactly following the procedure to minimize your risks for any post-operative complications.

Tests

Semen analysis may be done to check for male fertility and blockages of the vas deferens. This test will include the volume, number of sperm per milliliter, percentage of motile sperm, the shape of the sperm, and the presence of white blood cells. A semen culture may be performed to check for infection or inflammation.

Imaging may be done to look for conditions affecting the vas deferens, including ultrasound, computerized tomography (CT), or magnetic resonance imaging (MRI). In the case of a suspected malignancy, a biopsy may be performed.