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KMID : 0984920130150010041
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Journal of Skin Barrier Research
2013 Volume.15 No. 1 p.41 ~ p.47
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Basic Concept of Skin Barrier
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Youm Jong-Kyung
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Abstract
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The major functions of skin are to provide a protective shield against insults from the outside and at the same time to form a barrier capable of preserving the body`s internal milieu. The latter function, called the ``permeability barrier``, allows life in a terrestrial environment. Of all of skin`s many functions, this permeability barrier to the loss of body water is the most important task. Skin generates its permeability barrier in the outermost, anucleated layers of epidermis, the stratum corneum. Stratum corneum is explained as analogous to a brick wall in which the corneocytes are the bricks, and the ``bricks`` are embedded in a lipid-enriched ``mortar``. The permeability barrier is localized to this lipid-enriched mortar, called the extracellular matrix of the stratum corneum. The lipids are delivered to the extracellular space by the secretion of lamellar bodies. Three major types of lipids in the extracellular matrix are ceramides, cholesterol, and fatty acids that are presented in 1:1:1 mole ratio to form lamellar membranes between the corneocytes. Although the formation of a permeability barrier is of major importance, the skin has multiple defensive functions not only against toxins and allergens, but also against free radicals, UV-irradiation, mechanical/frictional insults, and changes in environmental humidity or temperature. Each of these protective functions is interdependent and intertwined with the other. Therefore, understanding how the defensive functions of skin are related to the permeability barrier is also required for the appreciation of skin barrier functions.
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KEYWORD
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Permeability barrier, Stratum corneum
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