Figure 2121

Photomicrograph of efferent ductules. The specimen in this photomicrograph was stained with picric acid and hematoxylin to better visualize the epithelial components of the efferent ductules. The efferent ductules are lined by pseudostratified columnar epithelium. The luminal surface has an uneven or wavy appearance because of the presence of alternating groups of tall columnar cells and cuboidal cells. The ductules are surrounded by several layers of circularly arranged smooth muscle (SM). Within the ductule lurnina are clumped spermatozoa (asterisks). Connective tissue (CT) makes up the stroma of the organ and contains blood vessels (BV) of various sizes. X120. Inset. This higher magnification of the pseudostratified epithelium shows columnar and cuboidal cells that contain sparse cilia. X500.

of surface-associated decapacitation factor containing epididymal fluid glycoconjugates. This process, called decapacitation, inhibits the fertilizing ability of the sperm in a reversible manner. The surface-associated decapacitation factor is later released during the capacitation process that occurs in the female reproductive tract just before fertilization. After maturation in the epididymis, sperm can transport their haploid content of DNA to the ovum; and after capacitation, they can bind to sperm receptors on the zona pellucida of the ovum. This binding triggers the acrosome reaction in which the sperm uses its acrosomal enzymes to penetrate the outer covering of the oocyte.

The principal cells in the pseudostratified epithelium of the epididymis are characterized by stereocilia

Like most of the excurrent duct system, the duct of the epididymis is also lined with a pseudostratified columnar epithelium. It contains principal cells (tall) and basal cells (short) (Fig. 21.23). The principal cells vary from about 80 fjim in height in the head of the epididymis to about 40 pm in height in the tail. Numerous long, modified microvilli called stereocilia extend from the luminal surface of the principal cells. The stereocilia vary in height from 25 pm in the head to approximately 10 pm in the tail. The small, round basal cells rest on the basal lamina. They are the stem cells of the duct epithelium. In addition, intraepithelial lymphocytes called halo cells are found in the epithelium. Under normal conditions, the epithelium of the epididymis is the most proximal level of the excurrent duct system in which lymphocytes are present.

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