ABSTRACT
Skin is the largest organ of the body, making up 16% of body weight, with a surface area of between 1.5 and 2.0 square meters (1,2). Skin functions as a mechanical barrier between internal organs and the external environment. It selectively permits exchange of water, electrolytes, and other substances. It functions as a physical as well as chemical protective barrier against ultraviolet (UV) radiations, toxic chemicals, and microorganisms (3). Skin is made up of three layers namely epidermis, dermis and hypodermis. Epidermis is the outer layer composed of a tough, supportive cell matrix and is comprised of a thin papillary layer and a thicker reticular layer. The main cells of the epidermis are the keratinocytes, which synthesize the protein keratin. Protein bridges called desmosomes connect the keratinocytes, which are in a constant state of transition from the deeper layers to the superficial. The dermis is the second layer providing the structural support of the skin, below which is a loose connective tissue layer. Hypodermis is a fat depot that maintains the moisture of the skin. Skin contains capillaries, lymphatic vessels, nerve endings, and glands which endow it with unique functions like a sensor that monitors and respond to changes in external environment, as a thermo regulator, an excretory organ of salt and water, and a store house of lipids. Thickness of the skin varies from 0.5 to 4.0 mm depending upon the function it serves. For example, the thickness of eye lids is thin and flexible compared to the thickness of palms of hands and soles of feet where it resists friction (4-8).
