ABSTRACT
For terrestrial animals, the skin's most important role is to protect the water-rich internal organs from the dry environment. This cutaneous barrier function resides in the stratum corneum. The water impermeability of this thin (10-20 Ilm) layer is 1000 times higher than that of other membranes of living organisms [1]. This is the same level as that of a plastic membrane with the same thickness [2]. The stratum corneum is composed of two components: protein-rich nonviable cells and intercellular lipid domains (Fig. 1). The lipid molecules in the intercellular domain form a bilayer structure. Because of this specific "brick and mortar" structure, the stratum corneum shows high water impermeability [1,3].
