Sunday, November 20, 2011

Skin

The largest organ of the human body is our skin; it does not only cover us and make us look presentable, but without it we'd literally evaporate. An adult carries 3.6 kilograms and 2 square meters of it. Skin acts as a waterproof, insulating shield, guarding the body against extremes of temperature, damaging sunlight and harmful chemicals. Skin is a huge sensor packed with nerves for keeping the brain in touch with the outside world. At the same time, skin allows us free movement, proving itself an amazingly versatile organ. 


Skin colour is due to melanin, a pigment produced in the epidermis to protect us from the sun's potentially cancer-causing ultraviolet (UV) rays. Dark-skinned people produce more numerous and deeper-coloured melanin particles. People with the darkest complexions are native to tropical regions, particularly those with few densely forested areas. 
Fair skin is an adaptation found in people from the northern latitudes, where the rays from the sun are relatively weak. Here the benefits of dark skin are outweighed by the need for bone-strengthening vitamin D, produced through exposure to UV rays. However sunnier environments bring the risk of serious skin damage. Australia, where the majority of the population is of northern European descent, has the world's highest rates of skin cancer, accounting for more than 80 percent of all cancers diagnosed there annually.   

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