Recent analyses of mummified or long-frozen human specimens have revealed that the outermost layer of our skin, the epidermis, is one of the most durable soft tissues of the body. The major function of the epidermis is to provide a protective barrier, and recent work now suggests that evolution has devoted an enormous amount of energy to providing this critical function. Several recent publications and three papers in this issue have shed new light on the complexity and redundancy of barrier function in the epidermis.
During terminal differentiation, stratified squamous epithelia, including internal wet and external dry epithelia, such as the epidermis, make a specialized structure termed the cell envelope (CE) (Reichert et al. 1993; Nemes and Steinert 1999). This is a key aspect of barrier function, as it provides a flexible physical protection against trauma...
