The ductus deferens is a paired muscular tube-like structure that transports sperm from the epididymis (Read more!) to the ejaculatory duct (Read more!). It arises from the tail of the epididymis and travels within the spermatic cord. This structure used to was also referred to as vas deferens. However, this term is no longer used as it is misleading and refers to a blood vessel rather than a duct.

The ductus deferens belongs to the internal genital organs of the male reproductive system. At its distal end, the ductus deferens is slightly dilated, and this enlargement is known as the ampulla of ductus deferens. It functions as a reservoir for sperm. The ampulla may have irregular outpouchings near its termination - they are known as the diverticula of ampulla.

Each ductus deferens unites with the excretory duct of the seminal vesicle (Read more!) to form the ejaculatory duct (Read more!). The ejaculatory duct joins the prostatic urethra. During ejaculation, smooth muscle cells within the walls of the ductus deferens contract, and these contractions move the sperm toward the ejaculatory duct and urethra. Along the way, it is joined by fluids from the seminal vesicle, prostate, and bulbourethral gland. Collectively, these fluids are called semen.

The ductus deferens is a relatively long structure, and each duct is approximately 11.81 - 17.72 inches (30 - 45 cm) long. The initial part of the ductus deferens appears convoluted, but it straightens once it goes further away from the tail of the epididymis (Read more!). It travels upward towards the inguinal canal, ascending along the medial side of the epididymis posterior to the testicle (Read more!). Within the spermatic cord, the ductus deferens lies within its posterior aspect.

The ductus deferens exits the inguinal canal via the deep inguinal ring. Here, it has an extraperitoneal position. Then, it curves around the inferior epigastric artery and ascends to reach the external iliac vessels. It crosses over the external iliac artery (Read more!) and external iliac vein (Read more!) and enters the lesser pelvis. In the lesser pelvis, the ductus deferens has a retroperitoneal position.

The ductus deferens then continue to travel in close proximity to the obliterated portion of the umbilical artery (Read more!), obturator nerve, obturator artery (Read more!), obturator vein, superior vesical artery (Read more!), inferior vesical artery (Read more!), and vesical veins. It crosses the mentioned structures on their medial sides and approaches the urinary bladder (Read more!). At the posterolateral angle of the urinary bladder, the ductus deferens crosses the ureter (Read more!) and further passes in the inferior direction along the base of the urinary bladder. Soon after, it expands, forming the ampulla. As mentioned, it ends by uniting with the excretory duct of the seminal vesicle (Read more!), forming the ejaculatory duct (Read more!).

Note: Vasectomy is a permanent male sterilization procedure. During this surgical procedure, the ductus deferens is cut and sealed or tied. It is performed at the superficial inguinal ring.

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Ductus deferens