Surface architecture of the mucosal epithelium of the cat trachea: I. Cartilaginous portion

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Abstract
The mucosal covering of the cartilaginous portion of the cat trachea was studied by correlated light, transmission‐electron, and scanning‐electron microscopy. While in some areas the ciliated pseudostratified epithelial lining is fairly smooth in contour, in other areas it contains longitudinally oriented, cilia‐lined clefts. Ducts from submucosal glands sometimes open into the base of these clefts, or into funnel‐shaped stomata that are lined by either ciliated or microvillus‐rich cells. Specialized epithelial cells are occasionally associated with the clefts or with other regions of surface epithelium. In single sections, these cells appear to contain a cilium‐lined vacuole, but serial sectioning has demonstrated that these apparent vacuoles actually are long intracellular inaginations in enormously elongated cells that extend longitudinally in the plane of the epithelium. The function of these cells is undetermined. Basal cells are attached to the lamina densa by means of hemidesmosomes that consistently lack peripheral densities; in contrast, the tall columnar cells have no hemidesmosomes.