Human Anatomy - Kotsan I. Y. 2009

Urogenital System
Reproductive Organs - Male Reproductive Organs
Epididymis

The epididymis is a small, elongated organ located along the posterior border of the Testis (Fig. 174). The epididymis serves as a reservoir for spermatozoa, where they are not only stored but also acquire fertilizing capacity. Anatomically, the epididymis consists of a rounded, expanded upper portion known as the HEAD of the epididymis (caput epididymidis), a middle portion called the body of the epididymis (corpus epididymidis), and a tapered lower portion known as the tail of the epididymis (cauda epididymidis), which turns sharply upward upon reaching the inferior pole of the testis. On the head of the epididymis, there is often a stalked, vesicular Structure called the Appendix of the epididymis, which represents a vestigial remnant of the mesonephric duct.

The head of the epididymis is composed of the efferent ductules of the testis, which emerge from the rete testis and course toward the epididymis. Each efferent ductule forms a cone-shaped lobule of the epididymis (lobuli epididymidis). There are typically 12 to 15 such lobules in the epididymis, separated by thin Connective Tissue septa. All efferent ductules empty into a single, highly coiled duct of the epididymis (ductus epididymidis), which largely occupies the body and tail of the epididymis. When straightened out, the epididymal duct reaches a length of 6 to 8 meters. In the tail of the epididymis, this duct continues as the vas deferens (Ductus deferens). The epididymis may also contain aberrant ductules (ductuli aberrantes)—blind-ending outgrowths of the epididymal duct and testicular efferent ductules that persist as remnants of the mesonephric tubules. Posterior to the head of the epididymis, embedded in the connective tissue, lies a whitish structure well-developed in children, known as the paradidymis, which is likewise a mesonephric rudiment.

Spermatozoa are produced exclusively within the convoluted seminiferous tubules of the testis. All other tubules and ducts of the testis and epididymis function as sperm-conveying pathways. Spermatozoa constitute a cellular component of semen, the liquid portion of which is formed by secretions from the Seminal Vesicles and the Prostate Gland.

Blood supply to the testis and epididymis is derived from the testicular artery (a branch of the Abdominal Aorta) and, in part, from the artery of the vas deferens (a branch of the umbilical artery).

Venous blood from the testis and epididymis drains via the testicular Veins, which form the pampiniform venous plexus within the Spermatic Cord and empty into the INFERIOR VENA CAVA on the right and the left renal vein on the left. The long pathway traveled by the venous blood draining from the testis creates less-than-optimal conditions for venous return. Consequently, venous stasis easily develops here, leading to Varicocele (pathological dilation of the pampiniform plexus veins).

Lymphatic vessels of the testis and epididymis drain into the lumbar Lymph Nodes.

The testis and epididymis receive sympathetic and parasympathetic innervation from the testicular nerve plexus, which also contains sensory nerve fibers.