Fine structure of the dorsal lingual epithelium of the crab-eating monkey, Macaca irus.

Light and electron microscopic observations of the dorsal lingual epithelium of the crab-eating monkey, Macaca irus, revealed three different regions: the epithelium on the anterior side of the filiform papillae, the epithelium on the posterior side of the filiform papillae, and the interpapillar epithelium. Whereas the basal and suprabasal cells are similar throughout, differences characterize the intermediate and surface layers. Keratohyalin granules appear predominantly in the intermediate layer of the epithelium on the anterior side of filiform papillae. In the epithelium on the posterior side of the filiform papillae, no keratohyalin granules are seen and, instead, tonofibrils are prominent. The cells begin to be significantly flattened. In the interpapillar epithelium, no keratohyalin granules and tonofibrils are seen, and the tonofilaments occupy almost the entire cytoplasm of the cells of the intermediate and surface layers, with the cells having larger volumes in these layers.