The skin is a major organ of the body forming 8% of its total mass and having an area between 1.1-2.2m2. It is the major interface between the body and the environment and covers the entire surface. It is continuous with mucosae at the various orifices and with lining tissue of organs like eyes and ears
Various structures including sebaceous glands, sweat glands, hair follicles and nails are formed by modifications of epidermis. Sebaceous glands secrete an oily substance called sebum and open on the sides of the hair follicles. Sweat glands are of two types,Merocrine and Apocrine. Merocrine glands are found throughout the body opening on the surface and secreting a clear watery fluid. Apocrine glands are found in the regions like axilla, areola, pubis, scrotum and perianal regions. Their ducts may open on the surface or into the hair follicle.
Dermis is made up of connective tissue consisting of matrix in which is embedded elastic and collagen fibres to give strength and elasticity. It also provides a compartment for blood vessels, lymphatics, nerves and cells associated with immunity. Receptors for the sensations such as touch, pain, pressure, warmth, cold and vibration senses are also found in the skin.
Circulation through the skin serves two major functions nutrition and conduction of heat to the environment.
1. Skin forms an effective barrier against infection by microbes.
2. It prevents dehydration and provides defense against chemical, osmotic, thermal and photic damage.
3. It limits and regulates heat loss.
4. It provides a major sensory surface with a range of receptors.
5. It has limited excretory and absorptive functions.
6. Skin also helps in the formation of vitamin D.
7. Its keratinization and high friction coefficient gives the skin a characteristic texture and helps in movement and handling of various substances.
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