Cellular envelopes of keratinized cells of the human epidermis

Abstract

Although the cellular envelope of the cornified human epidermal cells is known to become twice as thick (160 A) as that of the subjacent non-cornified cells (80 A), the trilaminar structure has never been demonstrated within this thickened “marginal band”. Evidence is presented that the marginal band (1) is a de novo product precipitated along the cytoplasmic side of the original plasma membrane, (2) has often outer and inner delimiting lines of high electron density, and (3) represents the true cellular envelope of the cornified human epidermal cells. The original trilaminar plasma membrane does not increase its thickness. It is seen as such in the lowermost layer of the stratum corneum, as a discontinuous line in the upper layers, and as a desquamated lamellar structure in the intercellular spaces. The membrane-coating granules are discharged outside of the original plasma membrane which prevents the direct contact of the discharged material with the newly developing marginal band.