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| Skin and Sweating |
Skin is an elastic and waterproof outer layer covering of our body. It protects our body from bacteria and is sensitive to heat, cold and pain. Skin is wear resistant sice it constantly renews itself by replacing the upper layer with fresh cells from below. Yet the thickness of the skin can vary from place to place on our body, it may be thin on our eyelids and thick on the soles of our feet.
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Skin is made up of two layers. The outer layer is called the Epidermis and the inner layer is called Dermis. The epidermis is porous and contains a chemical called Melanin which gives the skin its colour. The dermis contains sweat glands, hair roots, blood vessels and nerve ends which give us sensation. When we get injured internally on any part of our body it results in a blue bruise because the blood vessels under the skin is damaged and blood has seeped out of it into the skin tissue, giving it a blue appearance.
Our bodies maintain a constant temperature of about 98º Fahrenheit. There are occasions when the inner temperatures rise because of excessive exercise etc. or the outer atmospheric temperature becomes too high. On such occasions the blood vessels in the skin expand thus allowing the heat from the blood to escape into the air.
Tiny drops of water, called sweat, are produced by the sweet glands the they flow out of the pores in the skin thus reducing body temperature by evaporation. When one feels cold, the hairs in the skin become erect thus trapping a layer of air around them, preventing heat loss.
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Medical