Abstract
The ultrastructure of the crevicular epithelium of clinically healthy cat gingiva was similar to that of other non‐keratinizing oral epithelia. However, it differed in that the intercellular spaces were wide and extended as a continuous network from the basal lamina to the epithelial surface. Basal cells contained numerous mitochondria, Golgi apparatus, free ribosomes and a fine feltwork of evenly distributed tonofilaments. Hemidesmosomes were present in relation to the basal lamina. Cells in the intermediate layers showed a decrease in the number of organelles and an increase in concentration of tonofilaments, Superficial cells were further flattened and the remaining organelles commonly showed degenerative changes. Epithelial cells showed prominent microvilli extending into the intercellular spaces. Some of these formed desmosomes with similar processes of adjacent cells. Occasional randomly distributed tight junctions were also observed. Inactive basal melanocytes, more superficial Langerhans cells and leucocytes were seen between epithelial cells. The great majority of leucocytes were neutrophils and many of these ruptured as they approached the epithelial surface scattering their specific granules into the intercellular spaces. These findings are discussed in relation to the peculiar permeability of the gingival crevicular region of the oral mucosa to tissue fluid and leucocytes.