Human Anatomy - Kotsan I. Ya. 2009

Urogenital Apparatus
Genitals - Male Genitals
Ductus deferens

The vas deferens (ductus deferens) is a paired organ that is the direct continuation of the epididymal duct and terminates at the junction with the excretory duct of the Seminal Vesicle (Fig. 169). The length of the vas deferens is 40–50 cm, its outer diameter is about 3 mm, and the lumen diameter does not exceed 0.5 mm. The wall of the duct is quite thick; therefore, it does not collapse and is easily palpated within the Spermatic Cord.

Four parts are distinguished in the vas deferens. The initial, shortest segment, located posterior to the Testis and medial to its Epididymis, is called the testicular part. The next part, which ascends vertically to run within the spermatic cord and reaches the superficial inguinal ring, is termed the funicular (or spermatic cord) part. The inguinal part of the duct lies within the Inguinal Canal. Emerging from the inguinal canal through the deep inguinal ring, the vas deferens courses along the lateral and subsequently the inferior wall of the pelvic cavity until it merges with the excretory duct of the seminal vesicle. This section of the vas deferens is designated as the pelvic part. Within the lesser pelvis, the duct is located extraperitoneally (retroperitoneally). Along its course, it loops around the trunk of the inferior epigastric artery laterally, crosses the external iliac artery and vein, passes between the Urinary Bladder and the rectum, crosses the Ureter, reaches the Cytology/practical/108.html">Fundus of the bladder, and lies above the Prostate Gland adjacent to the contralateral duct of the opposite side. Approaching the bladder and the prostate gland, the terminal segment of the vas deferens forms a spindle-shaped dilatation known as the ampulla of the vas deferens (ampulla ductus deferentis). The length of the ampulla is 3–4 cm, and its maximum transverse dimension reaches 1 cm. In its lower part, the ampulla gradually narrows and, at the level of the upper margin of the prostate gland, joins the excretory duct of the seminal vesicle.

The wall of the vas deferens consists of mucous, muscular, and adventitial layers. The inner mucous membrane (tunica mucosa) is lined with Pseudostratified columnar epithelium and forms 3–5 longitudinal folds. In the region of the ampulla, the mucosa features pocket-like evaginations known as the ampullary diverticula (diverticuli ampullae). The muscular layer (tunica muscularis) is composed of three strata of Smooth Muscle tissue: inner and outer longitudinal layers, and a middle circular layer. This coat constitutes the thickest portion of the vas deferens wall, imparting a nearly cartilaginous firmness to it. In the ampulla of the vas deferens, the muscular layers are less distinctly defined. The outer adventitial layer (tunica adventitia) is formed of Connective Tissue interspersed with elastic fibers. It contains Blood Vessels and neural elements, blending imperceptibly into the surrounding connective tissue of the duct.