Fingernails and toenails function as protective coverings for the skin underneath, and fingernails help people to grasp and scratch at objects or itchy skin. Nails follow a gradual progression from the original cells to the extra bits that get trimmed off. Nails don't necessarily grow evenly; for example, the nails on your dominant hand most likely grow faster than the nails on your other hand. However, changes in the nail can signal that something's wrong. If you notice anything unusual about the way your nails look or grow, speak with a doctor.
Nail Matrix
Nails start out as epithelial cells in the nail matrix, which is underneath the skin. These cells gather in the area called nail root. The growing number of cells hardens into a plate-like mass that is pushed out past the cuticle and over the nail bed. Dr. David J. Leffell of the Yale School of Medicine, and author of "Total Skin," compares the action of the matrix to a pasta maker, "extruding new nail slowly but surely." The cuticle is an outgrowth of the top skin layer, called stratum corneum.
Nail Bed
The plate-like nail--appropriately named the nail plate--continues pushing its way down and out of the nail root as cells continue to divide. The layer of skin over which the plate moves is called the nail bed. At this point the nail becomes a window into possible health problems. Leffell notes that unusual spots and lines on the nail plate, and discoloration under the nail, can point to not only trauma, such as hitting your nail, but infections and malnutrition, among other possible disorders.
Overhanging Portion
The nail plate will continue to grow unchecked if you don't trim it; there's no mechanism in the matrix telling it to hold off dividing cells because the nail plate has reached a certain length. Nails grow approximately 1 mm per month; Binghamton University notes that it takes about six months for a point on the nail to go from the cuticle to the tip. If the overhanging portion of the nail begins to curve like a spoon, or the tip of your finger thickens for no reason, check with your doctor, as those can be signs of an illness.
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