Ultrastructural observations on myoepithelial cells and nerve terminals in the camel Harderian gland.

The myoepithelial cells and the nerve terminals of the Harderian gland in the one-humped camel were examined by using the transmission electron microscope. The myoepithelial cells are well developed, and composed of a cell body containing the nucleus, and many cytoplasmic processes. The cytological features are consistent with the function of the myoepithelial cell mainly as a contractile element, and possibly as a regulator for fluid transport. They are attached to the glandular cells of the end-pieces with desmosomes and interdigitating cytoplasmic processes. Densely packed myofilaments fill most of the cytoplasm, and micropinocytosis vesicles on the inner and outer borders are prevalent. The glandular end-pieces are innervated with unmyelinated nerve terminals which have been observed in the interstitial connective tissue. Nerve terminals without neurolemmal sheath penetrating the basal lamina and forming a direct neuroglandular contact with the glandular cells were observed. These intraglandular nerve terminals were found in direct contact with the myoepithelial cells, and contained small clear vesicles and a few larger dense granules.