November 23, 2012 11:05 am

Your skin is your body’s largest organ, larger than your heart or lungs or brain. Skin covers your whole body, from the top of your head to the soles of your feet. You could not live without your skin. Skin keeps germs and other harmful things out of your body. It keeps water, blood, and other fluids that you need inside your body.
You are always losing your skin and growing new skin. The outside layer of your skin is dead. It flakes off all the time. New skin grows to replace it.
Your skin has an outside layer called the epidermis. Under that is a layer called the dermis. Under those two layers is a layer of fat.
The epidermis protects the layers beneath it from minor scrapes, jabs, and sunburn. The bottom of your epidermis is always making new skin cells. The dead cells on the top of your skin are constantly dropping off.
The dermis is full of nerves and blood vessels. The nerves send signals to your brain when you touch something. The dermis gives your skin its toughness and strength. It also helps keep your body cool in hot weather and warm in cold weather. A scrape only bleeds if it’s deep enough to go through the epidermis and into the dermis.
There is a layer of fat under the dermis. This layer is thicker than both top layers of skin.
The top layer of skin has a chemical called melanin. Melanin gives your skin its color. The more melanin you have, the darker your skin is. Patches of skin with extra melanin make freckles.
Melanin protects your skin from the Sun’s harmful rays. Your skin makes more melanin when you are out in the Sun. More melanin gives you a tan.
Melanin has its limits. Too much sunlight is bad for your skin. Harmful rays from the Sun can burn your skin. They can cause skin cancer.
Hair is made of skin cells. A hair grows from a root under the skin. The hair grows up inside a shaft through the layers of skin. The part of the hair that you see is made of dead cells.
The color of hair, like the color of skin, comes from melanin. Melanin is made in the hair root. The hair of older people turns gray because the root stops making melanin.
The shape of the hair shaft gives you straight or curly hair. A round shaft makes straight hair. An oval-shaped shaft makes wavy hair. A comma-shaped shaft makes curly hair.
Fingernails and toenails are also made of skin cells. These nail cells are very hard. Nail cells start growing inside your fingers and toes. The cells die. New cells push the dead cells outward. This makes nails on your fingers and toes grow.
Plugged pores cause pimples (zits). Pores are openings in the skin. Dead skin cells can plug up a pore. The plug can make a blackhead or a whitehead on top of the skin.
Pores allow oil to get to the surface of your skin. This oil is the kind that gives you oily skin, not the kind that gets made into gasoline. The oil keeps your skin and hair from drying out. Groups of cells called glands make the oil. Oil glands are almost everywhere in your body. There are many oil glands on your face and scalp.
The oil cannot get out of a plugged pore. Soon a pimple or a red lump forms. The red lumps can leave scars. Squeezing a pimple can cause a scar.
Doctors can help teenagers with lots of pimples. Doctors can give them medicine that will help make the pimples go away.
Have you ever scraped your knee or cut your finger? Scabs grow over scrapes, cuts, and other wounds that bleed. The blood dries and hardens. The blood turns into a scab.
New cells grow under the scab. The cells join up and cover the cut. When the skin is healed, the scab drops off.
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