Interactions among stratum corneum defensive functions.

With the exception of vitamin D production, virtually all epidermal functions can be considered as protective, or more specifically, as defensive in nature. Yet, the term "barrier function" of the stratum corneum (SC) is often used synonymously with only one such defensive function, although arguably its most important, i.e., permeability barrier homeostasis. Regardless of their hierarchy of relative importance, these critical protective functions largely reside in the SC. In this short review, we explore the ways in which the multiple defensive functions of the SC are linked and interrelated, either by their shared localization or by common biochemical processes.