Bye-Bye Skin Cells

These old cells are tough and strong, just right for covering your body and protecting it. But they only stick around for a little while. Soon, they'll flake off. Though you can't see it happening, every minute of the day we lose about 30,000 to 40,000 dead skin cells off the surface of our skin.

So just in the time it took you to read this far, you've probably lost about 40,000 cells. That's almost 9 pounds (4 kilograms) of cells every year! But don't think your skin might wear out someday. Your epidermis is always making new skin cells that rise to the top to replace the old ones. Most of the cells in your epidermis (95%) work to make new skin cells.

And what about the other 5%? They make a substance called melanin (say: mel-uh-nun). Melanin gives skin its color. The darker your skin is, the more melanin you have. When you go out into the sun, these cells make extra melanin to protect you from getting burned by the sun's ultraviolet, or UV, rays.

That's why your skin gets tan if you spend a lot of time in the sun. But even though melanin is mighty, it can't shield you all by itself. You'll want to wear sunscreen and protective clothing, such as a hat, to prevent painful sunburns. Protecting your skin now also can help prevent skin cancer when you get older.The Dermis Is Under the Epidermis

The next layer down is the dermis (say: dur-mis). You can't see your dermis because it's hidden under your epidermis. The dermis contains nerve endings, blood vessels, oil glands, and sweat glands. It also contains collagen and elastin, which are tough and stretchy.

The nerve endings in your dermis tell you how things feel when you touch them. They work with your brain and nervous system, so that your brain gets the message about what you're touching. Is it the soft fur of a cat or the rough surface of your skateboard?

Sometimes what you feel is dangerous, so the nerve endings work with your muscles to keep you from getting hurt. If you touch something hot, the nerve endings in your dermis respond right away: "Ouch! That's hot!" The nerves quickly send this message to the brain or spinal cord, which then immediately commands the muscles to take your hand away. This all happens in a split second, without you ever thinking about it.