There is an interesting part of your body. It is always dying, and it is replaced every 28 days. Everywhere you go, you leave （微小的）pieces of it on the ground or the floor. It is the largest part of your body--your skin.
The skin makes up about 15% of your body weight and covers an aof about two square meters.
The skin is always replacing （自身）.As a result, dead skin cells are always falling off your body. It is said that much dirt in your house is mup of dead skin. But do you know the skin has some important values?
The skin（保护）the inside parts of your body. It works hard to keep your body warm or cool. Holes in the skin can open or close to help（控制）body heat.
Your skin is not only a "protector" but aa "feeler". It feels touch or pain.Parts of cells that feel touch are connected to the brain. When you touch something, your brain decides wto do and then tells your muscles（肌肉）.But the parts that feel pain are connected straight to muscles.If these feel （急剧的,突然的）pain,they tell the muscles to move quickly.The muscles don't need the brain to tell them to jump. Do you think it's ran amazing part of your body?
