Surface adaptations of the vertebrate epidermis to friction.

Epidermal surfaces in representative vertebrates specialized for lowered or increased friction were studied with the scanning electron microscope. Microvillous and microridged patterns predominate in aquatic vertebrates. In squamate reptiles, the complex and varied ornamentation of the Oberhäutchen functions both in adhesive modifications and in modulating surface reflectivity. Frictional surfaces in birds and mammals are characterized more by anatomical than by cytologic specializations, the detailing of surface cells being mostly a function of turnover rate.