The ultrastructure of the keratinizing epithelia of the incisor and molar gingivae of the albino rat: similarities and differences.

Abstract

AbstractUltrastructural differences suggest that the keratinizing epithelium of the incisor gingiva (IG) is more rigid and durable than that of the molar gingiva (MG). The more numerous and larger collagen fibrils of the lamina propria, the more dense and homogeneous basal lamina, the more numerous anchor filaments distributed along the basal lamina and the larger and more frequently occurring hemidesmosomes along the base of basal cells all provide the IG epithelium with a firmer base and stronger attachment than the MG. The presence of many and long filaments in the IG and their aggregation into bundles inserted into the attachment plaques of desmosomes also suggest that this epithelium is tougher than the MG. This is further emphasized by the larger size of the desmosomes and their more frequent occurrence along the plasma membrane of cells of the IG. The ultrastructure of membrane‐coating granules and their role in membrane modifications appear to be the same in both the IG and MG. As the irregularly shaped keratohyalin granules of the IG increase in size, the dense amorphous material spreads out over the bundles of tonofilaments. On the other hand, as the spherical keratohyalin granules of the MG grow in size, they maintain their spherical shape and do not appear to be associated with or spread out over the filaments. The flattened horny cells of the IG with smooth contours and joined together by closely spaced desmosomes appear to be more protective and less easily detached by the abrading stress of mastication than those of the MG, which are irregular in shape with convoluted cell membranes and widely spaced desmosomes.