Bodily Defenses Image Map
What happens when the sun hits your skin?  Either you get tanned or you get burned.  Why do some people tan while other people burn?  How does sunscreen help?  What happens when you have prolonged exposure to the sun?  What the sun does to your skin is very important because the skin is your first line of defense!

What the sun does to your skin:
Sunburn is caused by ultraviolet light from the sun. These rays activate melanin, which is the body's protective pigment against the sun, and turn the melanin brown. This creates a tan.  Radiation has to hit something in order to dissipate its energy.  Melanin provides target molecules that safely absorb radiation energy.  However, sometimes the body can't handle the amount of rays that the sun is giving off.  In this case, the sun will actually burn the skin - a sunburn!

What causes your skin to be red from a sunburn?

Everyone knows that you get a sunburn from being outside too long.  What is happening under your skin to allow you to burn? Don't confuse a sunburn with a burn that you will get from a fire, because they are different.  The red color is partly because of increased blood flow to the injured area.  When cells' membranes are damaged, certain chemicals leak out.  Two of these are histamine and bradykinin, which are peptides that cause the blood vessels to dilate.  As we have learned, this reaction is common when a part of the body has been injured.  Also, the body will begin certain inflammatory processes, which causes the pain and soreness felt as your body attempts to heal itself.  When a burn is severe, you can actually have blisters, caused by the movement of protective cells in the blood to the extremely injured areas. 


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