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Scanning electron microscopy of tympanic membrane epithelium during in vitro migration.

The en masse locomotion in tissue culture of stratified squamous epithelium of the tympanic membrane and cholesteatoma is a unique feature of these epithelia. A scanning electron microscopy study of cultures was carried out to seek features of surface architecture that might throw light on this special activity. Differences from cultures of non-migratory stratified squamous epithelium include the following: numerous lamellae emanating from the top surface of cells at the leading edge, a ridge of spent leading edge cells behind that edge, a cap of keratin behind the latter and large balloon-like swelling of cells is prevalent in the trailing edge. It is suggested that differentiation of migrating stratified squamous epithelium in tissue culture is towards specialized cells active in migration as shown by the leading and trailing edge cells, as well as towards keratinization as shown by the keratin cap.