Ultrastructure of the Ductuli Efferentes in Monkeys

Abstract

The epithelium of the ductuli efferentes in monkeys consists primarily of ciliated and nonciliated cells, although occasional macrophages, intraepithelial lymphocytes and basal cells are present. Beneath the epithelium is a thick basal lamina (2–8 µm) deep to which are found dense bundles of collagen fibers. The ovoid or spherical nuclei (8 × 11 µm) of the ciliated cells are large, contain predominantly electron lucent euchromatin and are located in the middle or apical regions of the cell. The smaller nuclei (5–8µm) of the nonciliated cells are situated near the basal lamina of the epithelium and are bizarre-shaped due to numerous indentations of the nuclear envelope. They also contain electron-dense heterochromatin especially adjacent to the inner nuclear envelope. The cytoplasm of both cell types extends from the basal lamina to the tubule lumen. The ciliated cells are characterized by numerous mitochondria and a lightly stained cytoplasm. A few dense bodies, presumably lysosomes, are also present in the supranuclear cytoplasm. In addition, well developed ciliary rootlets containing a regular pattern of 70–80 nm cross striations frequently extend to the perinuclear zone far beyond the apical cytoplasm. Micropinocytotic vesicles, membrane-bound dense bodies, and numerous vacuoles of different sizes filled with flocculent material are densely packed in the cytoplasm of the nonciliated cells. Some mitochondria and lysosomes are also scattered throughout the cytoplasm of these latter cells. In both cell types there is a paucity of other organelles, particularly Golgi and endoplasmic reticulum. These morphological features suggest a low capacity for protein synthesis and elaboration of secretory products. The nonciliated cells are known to absorb large quantities of fluid from the tubular lumen. The micropinocytotic vesicles and numerous vacuoles in these cells are likely involved in this process. The abundant mitochondria in the ciliated cells are no doubt necessary to provide energy for ciliary motion.