Facts of lifeThe Secrets of Fingernails [Archives:2005/869/Health]
By Dr. Khaled alNsour
For the Yemen Times
Trim. File. Polish. With the popularity of manicures and pedicures, you might come to the false conclusion that nails are unnecessary parts of our body that we decorate for the sake of vanity. But, there is a real, evolutionary reason for nails.
Made up of long fibers of the protein keratin (the same stuff that your hair is made of), nails not only protect the fingertips and toes, they also help us grab or pick up objects – in the same way that beaks and claws of birds and animals help them handle food or objects.
Nails grow from a “growth plate” located at the base of the nail. It's the half-moon shaped area at the base of the nail near where the skin connects. Nails are fomed by special cells called epithelium. Epithelial cells grow from the growth plate and as they mature, they are pushed outward. During growth they die and the inside of the cells become filled with a hard protein called “Keratin”. It is the keratin that makes our nails hard and tough.
Nail growth is related to the length of a finger, so the fastest growing nail is the one on the middle finger. The nail on the pinky finger is the slowest. If you're right-handed, the nails on that hand will grow faster than on the left. The opposite is true if you're left handed. Fingernails grow four times as fast as toenails and grow the fastest during the day, during the summertime and among younger people.
Most animals have some form of nail, even if it doesn't look like it sometimes. Cats and dogs have a sharpened, curved nail (we call these claws). And horses have a thick, round stump of a fingernail (we call these hooves).
Why do finger nails keep growing?
A special growth area (called the matrix) at the base of the nail controls the speed of the finger nails' growing. The matrix lies in a deep groove in the skin dermis (the thick inner layer alive with nerves and blood vessels) and makes nail material)a dead, hoof-like protein, called keratin. It makes nails constantly)from birth to death)at an average rate of 0.004 inches (0.1 mm) each day, or 1.5 inches (36.5 mm) in a year.
Although fingernails grow four times faster than toenails, the matrix doesn't make nails at a steady rate. Nails grow faster when it's warm, when we're young, when we apply pressure to the nails)like playing the piano or biting, cutting, filing, polishing, or scrubbing them. Nails grow slower when the matrix is short of blood, when the blood contains stuff that stunts growth (like chemotherapy material or cigarette by-products), when we suffer malnutrition, or have a high fever.
Do they grow after death?
Death stops growth. However, after death, skin dries and shrinks. When it shrinks back from nails, the fingernails (and toenails) appear to lengthen because more nail shows.
Why are toenails thicker than fingernails?
Friction and fungus thicken toenails. Toenails take a beating from socks, shoes, and generally being at the foot end of the human body where the weight bearing goes on. They're made from the same dead skin tissue as fingernails but are two to three times thicker.
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