The differentiation of chick embryonic skin. An electron microscopic study with a description of a peculiar epidermal cytoplasmic ultrastructure

The ontogeny of chick embryonic skin was studied at the electron microscopic level. An earlier onset and gradual differentiation of the dermis contrast the later and expedient epidermal differentiation. The fate of the two epidermal cell types is very different. Pericytes and their derivatives constitute a transient embryonic structure whereas basal cells and their derivatives form the adult keratinizing epidermis. The differences in ultrastructural morphology of the two epidermal cell types are slight on the 12th day of incubation but thereafter become increasingly apparent as differentiation proceeds. The ultrastructure of basal cells and their derivatives suggests that these cells exert a secretory function felt to be related to production of filaments.