| Abstract: | The monkey epididymis was subdivided into four regions: initial segment (continous with the ductuli efferentes), head, body and tail. The initial segment possesses a very tall columnar epithelium (108 ± 4 μm). Epithelial height in the head, body and tail is diminished to 81 ± 5 μm, 69 ± 2 μm, and 50 ± 5 μm, respectively. The pseudostratified epithelium is composed of four main cell types: principal, apical and basal epithelial cells, and intraepithelial lymphocytes. Occasional macrophages are also found in the epithelium. The tall, narrow, columnar principal cells demonstrate morphological features characteristic of absorption and secretion. An unusual feature, apparently unique to the primate, is the presence of deep invaginations of the apical cytoplasm which contain membrane-bounded vacuoles. Similar, but larger vacuoles are present among the stereocilia and in the tubular lumen. Large clusters of mitochondria and electron-dense membrane-bounded granules characterize the infranuclear region of the cytoplasm. Principal cells are studded with closely aligned stereocilia. Their nuclei are spindle-shaped in the initial segment and first portion of the head region, but become highly infolded in the distal head, body and tail portions. The apical or mitochondrion-rich cells possess a cytoplasm which extends from the base of the epithelium to the tubular lumen. Basal cells contain few organelles and are found throughout the length of the duct. Arterioles and capillaries appear to penetrate directly into the epithelium from the underlying connective tissue; however, the basal lamina of the epididymal duct always intervenes between the endothelium of the blood vessels and the epithelial cells. Several of the above observations have not been noted in rodents and other mammalian species and may be unique to the primate. |
