Barrier Development, Ultrastructure, and Sulfhydryl Content of the Fetal Epidermis

Synopsis--Previous studies have demonstrated that the PERMEABILITY BARRIER of the SKIN resides principally in the stratum comeurn and that in mammalian species this barrier is fully developed at birth. In the present study, development of the stratum comeurn was observed during fetal life of the rat and the guinea pig. Measurements were made of the water permeability of fetal skin at several periods in fetal life through tenn. At the same periods, tissues were examined for changes in fine STRUCTURE and in SULFHYDRYL CONTENT. The data revealed that genesis of the permeability barrier starts in the last quarter of gestation and is concluded just before term. Concurrent with the final stages of formation of the permeability barrier sulfur metabolism is intensified. The horny layer matures as evidenced by increased cellular cohesion and aggregation of tonofilaments into well-defined bundles; differentiation of the stratum granulosum and stratum comeurn goes to completion. At birth, the ultrastructure of the stratum comeurn is indistinguishable from that of the adult.