The ductus deferens (also known as vas deferens) is a tubular paired muscular organ that begins from the tail part of the epididymis.

It is approximately 45 - 50 cm long and 0.5 - 1 mm wide. As a part of the spermatic cord (read below), it travels upwards, and exits the inguinal canal and enters the true pelvis between the rectum and bladder.

The ductus deferens has a connection with the urethra, and it forms the ejaculatory duct that opens at the prostatic urethra.

The main function of the ductus deferens (also called the vas deferens) is to transport sperm from the epididymis to the ejaculatory duct.

The ductus deferens has four parts:

Testicular part - extends along the posterior border of the testicle from the tail of the epididymis to the superior pole of the testicle;
Funicular (also spermatic) part - travels within the spermatic cord to the superficial inguinal ring;
Inguinal part - passes through the inguinal canal, extending from the superficial to the deep inguinal ring;
Pelvic part - travels down and back from the deep inguinal ring along the wall of the pelvis; crosses the external iliac artery and vein, ureter and reaches the fundus of the urinary bladder, where the ductus is enlarged; this enlargement is called the ampulla of the ductus deferens and it functions as a reservoir for sperm.

NOTE: Vasectomy, which is a surgical procedure of male sterilization, is performed at the superficial inguinal ring. During the procedure, the ductus deferens is cut and sealed or tied.

Spermatic cord

The spermatic cord is formed when the testicle and epididymis descend through the inguinal canal to the scrotum.

It has a soft consistency, and it goes from the tail of the epididymis to the inner opening of the inguinal canal.

The spermatic cord contains the following structures:

Ductus deferens (except its pelvic part)
Blood vessels, nerves, and lymphatic vessels
Coverings of the testicle and epididymis (except the tunica vaginalis testis)

The spermatic cord from the outside is covered by loose connective tissue.

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Ductus deferens