Figure 2122

Photomicrograph of human epididymis. This photomicrograph of a H&E-stained section shows the highly coiled ductus epididymis. Its coiled nature is reflected in the variously shaped profiles of the duct. Within the connective tissue are numerous profiles of blood vessels (BV). The vessels tend to follow the duct; thus they, too, reflect multiple profiles of several vessels. The section of the duct within the rectangle is shown at higher magnification in Figure 21.23. x30.

Epididymal cells function in both absorption and secretion

Most of the fluid that is not reabsorbed by the efferent ductules is reabsorbed in the proximal portion of the epididymis. The epithelial cells also phagocytose any residual bodies not removed by the Sertoli cells as well as sperm that degenerate in the duct. The apical cytoplasm of the principal cells contains numerous invaginations at the bases of the stereocilia, along with coated vesicles, multivesicular bodies, and lysosomes (Fig. 21.24).

The principal cells secrete glycerophosphocholine, sialic acid, and glycoproteins, which, in addition to the glycoca-lyx and steroids, aid in the maturation of the sperm. They have numerous cisternae of rER surrounding the basally located nucleus and a remarkably large supranuclear Golgi apparatus. Profiles of sER and rER are also present in the apical cytoplasm.

The smooth muscle coat of the duct of the epididymis gradually increases in thickness to become three-layered in the tail

In the head of the epididymis and most of the body, the smooth muscle coat consists of a thin layer of circular smooth muscle resembling that of the efferent ductules. In the tail, inner and outer longitudinal layers are added. These three layers are then continuous with the three smooth muscle layers of the ductus deferens, the next component of the excurrent duct system.

Differences in smooth muscle function parallel these morphologic differences. In the head and body of the epididymis, spontaneous, rhythmic peristaltic contractions serve to move the sperm along the duct. Few peristaltic contractions occur in the tail of the epididymis, which serves as the principal reservoir for mature sperm. These sperm are forced into the ductus deferens by intense contractions of the three smooth muscle layers after appropriate neural stimulation associated with ejaculation.

\ dense connective tissue

basal cells

J-smooth muscle

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