The vas deferens is a muscular tube in the male reproductive system. It transports mature sperm from storage for ejaculation, a process essential for male fertility.
Where It Is Located
Each male possesses two vasa deferentia, one originating from each testis. These tubes begin at the tail of the epididymis, a coiled structure on the back of each testicle where sperm mature and are stored. From the epididymis, the vas deferens ascends into the pelvic cavity as part of the spermatic cord, a structure that also contains blood vessels, nerves, and lymphatic vessels.
The vas deferens then travels through the inguinal canal, a passageway through the abdominal wall. After exiting the inguinal canal, it loops over the ureter and descends behind the bladder. Near the base of the bladder, it widens to form an ampulla before joining with the duct of the seminal vesicle to create the ejaculatory duct. These ejaculatory ducts then pass through the prostate gland and empty into the urethra, the tube that carries both urine and semen out of the body.
How It Works
The primary function of the vas deferens is to transport mature sperm from the epididymis to the ejaculatory duct during ejaculation. This is achieved through rhythmic contractions of its thick smooth muscle walls, a process known as peristalsis.
The vas deferens is notably long, measuring 30-45 centimeters (12-18 inches). Its muscular wall is thicker than any other hollow organ, supporting forceful sperm propulsion. While primarily for transport, it also contributes to limited sperm storage and fluid absorption.
When Its Function Is Altered
Intentionally altering the vas deferens’ function is the basis of a vasectomy, a permanent male birth control. During this outpatient procedure, the tubes are cut, sealed, or blocked, preventing sperm from mixing with semen during ejaculation. This results in sterility, as sperm cannot reach the urethra, though fluid ejaculation still occurs.
Other conditions can affect the vas deferens, impacting fertility. Congenital absence of the vas deferens (CAVD) means an individual is born without these tubes, causing infertility often linked with genetic conditions like cystic fibrosis. Blockages can also occur due to infections, inflammation (vasitis), trauma, or cysts, preventing sperm transport. In such cases, sperm may be produced in the testes but cannot exit the body, leading to azoospermia (lack of sperm in ejaculate).