Figure 4.

SC architecture. During the final trimester, a remarkable process of epidermal differentiation culminates in formation of the SC. The SC is in direct contact with the environment, making it the first line of defense and consists of ∼16 corneocyte cell layers that are embedded in the lipid matrix. Lipids are synthesized in the nucleated cells of the epidermis and stored in lamellar bodies in the spinous layer. They are secreted from the lamellar bodies into the intercellular spaces at the interface between the granular layer and the SC. The thickness is 10–40 μm, varying with anatomical location. The corneocytes are interconnected within and between layers via corneodesmosomes. The protein filaggrin undergoes proteolysis to form NMF, which is responsible for SC hydration, water-handling properties, and plasticity. By design, the SC structure is mechanically tough and difficult to penetrate from the outside. NMF, natural moisturizing factor. To see this illustration in color, the reader is referred to the web version of this article at www.liebertpub.com/wound