The vas deferens, also known as the ductus deferens or sperm duct, is a component of the male reproductive system. These long, muscular tubes play a role in the journey of sperm within the body. Its function involves the movement of sperm.
Where It Is Found
The vas deferens is a muscular tube found within the spermatic cord, which also contains blood vessels and nerves. Humans have two vasa deferentia, one originating from each testis. Each tube begins at the tail of the epididymis, a coiled tube located on the back of the testicle where sperm mature and are stored.
From the epididymis, the vas deferens ascends into the pelvic cavity, looping over the urinary bladder. It then joins with the duct from the seminal vesicle to form the ejaculatory duct, which connects to the urethra. Each vas deferens measures approximately 30 to 45 centimeters (about 12 to 18 inches) in length and has a narrow diameter of about 2 to 3 millimeters. Its walls are thick, composed of three layers of smooth muscle.
How It Transports Sperm
The role of the vas deferens is to transport mature sperm from the epididymis to the urethra in preparation for ejaculation. While the testes produce sperm and the epididymis stores and matures them, the vas deferens acts as a conduit, not a site of sperm production.
The movement of sperm through the vas deferens is achieved through a process called peristalsis. During sexual arousal, the smooth muscle layers within the walls of the vas deferens undergo rhythmic contractions. These wave-like contractions propel the sperm forward along the tube. As sperm moves through the vas deferens, it eventually mixes with fluids from other accessory glands, such as the seminal vesicles and the prostate gland, forming semen.
Procedures Affecting the Vas Deferens
The vas deferens can be involved in several medical procedures and conditions, most notably vasectomy. A vasectomy is a surgical procedure for male contraception, where the vas deferens are cut, tied, or sealed to prevent sperm from traveling from the epididymis to the urethra. This procedure blocks sperm passage, making it a highly effective method of birth control while still allowing seminal fluid production.
Beyond contraception, the vas deferens can also be affected by congenital conditions, such as Congenital Bilateral Absence of the Vas Deferens (CBAVD). Individuals with CBAVD are born without one or both of their vas deferens, which is often associated with mutations in the gene responsible for cystic fibrosis. This condition prevents sperm from exiting the body naturally, leading to male infertility. Additionally, the vas deferens can experience blockages due to infection, inflammation, or injury, which can also impede sperm transport and impact fertility.