Structure and function of the stratum corneum permeability barrier

Abstract

Abstract The main function of the epidermis is to generate an impermeable outer layer, the stratum corneum. The stratum corneum can be considered morphologically and functionally to represent a two‐compartment system composed of: (1) anucleate corneocytes (the bricks), largely composed of fibrous protein networks; and (2) the intercellular matrix (the mortar), predominantly composed of neutral lipid. Whereas much prior and current work on the stratum corneum has focused on the protein biochemistry leading to the formation of the keratinized corneocyte (“keratinization”), this paper is concerned with the formation, composition, and function of the intercellular matrix of the stratum corneum. For those interested in permeability barrier function, percutaneous transport, and the cutaneous reservoir, as well as most inherited disorders of cornification, it is critical to understand the “mortar,” for it is this domain that logically regulates all of these important phenomena.