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The most important function of skin is to form a barrier between the inside of human and the external environment. This barrier regulates water loss as “inside-outside” barrier and protects against mechanical, chemical, and microbial assaults from external environment as “outside-inside” barrier. To perform barrier`s function, epidermis undergoes keratinization. Keratinization is a process in which epidermal cells progressively mature from basal cells to the lifeless, flattened corneocytes of stratum corneum(SC). The SC contains a complex mixture of polar and nonpolar lipids in its extracellular spaces. These lipids have been investigated desquamation. The composition of these lipids varies from species to species, with the body region and the degree of keratinocyte differentiation. Lamellar bodies play a key role in delivering the lipids from cells of the stratum granulosum into the extracellular spaces of the SC and they contain glucosylceramides, phospholipids, and cholesterol. These lipids are delivered by exocytosis of lamellar bodies and converted by beta glucocerebrosidase and phospholipids into the ceramides and fatty acids. Therefore, SC contains 50% ceramides, 20% cholesterol and 15% free fatty acids with very little phospholipid and structure of lamellar lipid bilayer is performed in extracellular space. Our paper is a review for the structure and characteristics of lipids between keratinocytes.
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