In addition to keeping the harsh external environment away from our own critically sensitive internal biological environments, our skin acts as a regulator of body temperature and a sealant against fluid loss.
But our skin is the organ perhaps most commonly disregarded, and must withstand assault from a daily barrage of factors including sunlight and UV irradiation, wind, temperature extremes, and the daily insult of cuts, nicks, and scrapes, which leave it susceptible to invasion by fungus, bacteria, and viral invaders.
You can appreciate the many roles of skin by looking at its two major layers-the outer epidermis, and the deeper underlying dermis.
Epidermis
The epidermis is continually exposed to the environment and sustains most of the injury to the skin. As a result, it is shed and regenerated on a daily basis. Its major role is to produce the stratum corneum-a waterproof, semi-permeable membrane on the outermost portion of the epidermis that acts to prevent water loss from the tissues it surrounds. When this upper layer is injured-as can occur with minor scrapes and cuts-it simply regenerates itself without scar formation. The same is not true for deeper injuries.
Dermis
Residing just below the epidermis is the dermis, which constitutes 90% of total skin thickness. Because of its rich collagen content, the dermis is the strength layer of the skin.
Copyright 2009 NBC Health
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