The pseudostratified columnar epithelium contains tall, nonciliated columnar cells and short, round cells that rest on the basal lamina. The short cells appear identical to those of the rest of the excurrent duct system. They are the stem cells from which the columnar cells are derived. The columnar cells have the morphology of protein-secreting cells, with a well-developed rER and large secretory vacuoles in the apical cytoplasm.
The secretion of the seminal vesicles is a whitish yellow, viscous material. It contains fructose, which is the principal metabolic substrate for sperm, along with other simple sugars, amino acids, ascorbic acid, and prostaglandins. Although prostaglandins were first isolated from the prostate gland (hence the name), they are actually synthesized in large amounts in the seminal vesicles. Contraction of the smooth muscle coat of the seminal vesicles during ejaculation discharges their secretion into the ejaculatory ducts and helps to flush sperm out of the urethra. The secretory function and morphology of the seminal vesicles are under the control of testosterone.
The prostate, the largest accessory sex gland, is divided into several morphologic and functional zones.
The prostate is the largest accessory sex gland of the male reproductive system. Its size and shape are commonly compared to those of a walnut. The main function of the prostate
FIGURE 22.25 • Photomicrograph of human spermatic cord. a. This low-magnification photomicrograph shows a cross section of the spermatic cord containing several structures. These include the ductus deferens, the accompanying testicular artery and vein, and veins of the pampiniform plexus. 15. Inset. A higher magnification of a pampiniform vein. Note the bundles of longitudinal smooth muscles (cut in cross section) in the tunica adventitia and tunica intima. 55. b. This cross section of the ductus deferens shows the thick muscular wall organized in three distinct smooth muscle layers: an inner longitudinal (SM(L)), middle circular (SM(C)), and outer longitudinal (SM(L)). 100. Inset. A higher magnification shows the pseudostratified epithelium lining the ductus deferens. The tall principal cells possess long microvilli (stereocilia; arrows). The basal cells are in close proximity to the basement membrane and possess spherical nuclei. 215.
gland is to secrete a clear, slightly alkaline (pH 7.29) fluid that contributes to the formation of seminal fluid. The gland is located in the pelvis, inferior to the bladder, where it surrounds the prostatic part of the urethra. It consists of 30 to 50 tubuloalveolar glands arranged in three concentric layers: an inner mucosal layer, an intermediate submucosal layer, and a peripheral layer containing the main prostatic glands (Fig. 22.27). The glands of the mucosal layer secrete directly into the urethra; the other two layers have ducts that open into the prostatic sinuses located on either side of the urethral crest on the posterior wall of the urethra.
The adult prostatic parenchyma is divided into four anatomically and clinically distinct zones:  The central zone surrounds ejaculatory ducts as they pierce the prostate gland. It contains about 25% of the glandular tissue and is resistant to both carcinoma and inflammation. In comparison to the other zones, cells in the central zone have distinctive morphologic features (a more prominent and slightly basophilic cytoplasm and a larger nuclei displaced at different levels in adjacent cells). Recent findings suggest that this zone originates embryologically from the inclusion of mesonephric duct cells into the developing prostate.