Nails

Nails are the hard, smooth coverings at the tips of your fingers and toes. They are made of a tough material called keratin, the same stuff that makes up your hair and the outer layer of your skin. Every person has 20 nails, one on the end of each finger and toe. They protect the soft tips of your digits and help you pick up small things.

A nail has several parts. The hard part you can see is called the nail plate. The pink color underneath comes from tiny blood vessels in the skin below it. At the base of each nail is a pale half-moon shape called the lunula. Behind that, hidden under your skin, is the nail root. The root is where new nail cells are made. As fresh cells grow in, they push the older cells forward. The older cells flatten, harden, and die. That is why cutting your nails does not hurt. The part you trim is already dead.

Nails grow slowly. Fingernails grow about an eighth of an inch each month. That is roughly the thickness of two pennies stacked together. A whole fingernail takes about six months to grow from the root to the tip. Toenails are even slower. They can take more than a year to grow out fully. Nails grow a little faster in summer than in winter, and a little faster on the hand you write with.

Nails do more than just sit there. They help you scratch an itch, peel a sticker, or pick up a coin from a flat table. Without nails, your fingertips would be much weaker at gripping small objects. Nails also act as armor. They guard the bone at the end of each finger and toe from bumps and pressure.

Doctors sometimes look at a person's nails for clues about health. Pale, ridged, or oddly shaped nails can hint that something inside the body is off. Most of the time, though, nails just need basic care. Keeping them clean and trimmed helps stop dirt and germs from building up underneath. Biting your nails is a common habit, but it can carry germs from your hands straight into your mouth.

Other animals have versions of nails too. Cats and dogs have claws, horses have hooves, and birds have talons. All of them are made from the same simple material your own nails are.