FIGURE 22.23 • Photomicrograph of human ductus epididymis. This higher magnification of the rectangular area in Figure 22.22 reveals the two cell types of the epididymal epithelium, the principal cells and the basal cells. Stereocilia (arrows) extend from the apical surface of the principal cells. The nuclei of the basal cells are spherical and are located in close proximity to the basement membrane, whereas the nuclei of the principal cells are cylindrical and conform to the columnar shape of the cell. Surrounding the duct epithelium is a layer of circularly arranged smooth muscle cells. The duct lumen contains numerous sperm. 250.
vesicle and continues through the prostate gland to the urethra as the ejaculatory duct.
The ductus deferens is lined with a pseudostratified columnar epithelium that closely resembles that of the epididymis (Plate 89, page 824). The tall columnar cells also have long microvilli that extend into the lumen. The rounded basal cells rest on the basal lamina. Unlike the epididymis, however, the lumen of the duct does not appear smooth. In histologic preparations (Fig. 22.25), it appears to be thrown into deep longitudinal folds throughout most of its length, probably because of contraction of the thick (1 to 1.5 mm) muscular coat of the duct during fixation.
The ampulla of ductus deferens has taller, branched mucosal folds that often show glandular diverticula. The muscle coat surrounding the ampulla is thinner than that of the rest of the ductus deferens, and the longitudinal layers disappear near the origin of the ejaculatory duct. The epithelium of the ampulla and ejaculatory duct appears to have a
FIGURE 22.24 • Electron micrograph of epididymis. a. Electron micrograph of the epididymal epithelium, showing principal cells (PC) extending to the lumen and a basal cell (BC) limited to the basal portion of the epithelium. Profiles of sperm (S) are seen in the lumen. The apical cytoplasm of the principal cells exhibits numerous long microvilli (stereocilia). 3,000. b. Apical surface of the epithelial cell with its numerous long microvilli (stereocilia). The middle piece of a sperm (S) is evident in the lumen. The small, light circular profiles (arrowheads) are endocytotic vesicles. 13,000.
secretory function. The cells contain large numbers of yellow pigment granules. The wall of the ejaculatory duct does not have a muscularis layer; the fibromuscular tissue of the prostate substitutes for it.
The paired seminal vesicles secrete a fluid rich in fructose.
The seminal vesicles are paired, elongate, and highly folded tubular glands located on the posterior wall of the urinary bladder, parallel to the ampulla of the ductus deferens. A short excretory duct from each seminal vesicle combines with the ampulla of the ductus deferens to form the ejaculatory duct. Seminal vesicles develop as evaginations of the mesonephric (Wolffian) ducts in the region of future ampullae. The wall of the seminal vesicles contains a mucosa, a thin layer of smooth muscle, and a fibrous coat (Fig. 22.26). The mucosa is thrown into numerous primary, secondary, and tertiary folds that increase the secretory surface area (Plate 91, page 828). All of the irregular chambers thus formed, however, communicate with the lumen.