Humans have fingernails to protect sensitive skin on the fingers from cuts, burns and other damage. Nails on the fingers help people pick and pry, essentially serving as natural tools. They help with grooming by letting people brush off dirt and contaminants from skin and help people perform simple tasks like scraping off dog hairs from garments.
Fingernails appear over each finger, just as toenails cover all ten toes. Fingernails and toenails are made up of a substance called keratin, which also forms human hair and exists as the microscopic top layer of skin. Nails appear to start at the base of a cuticle, which is a U-shaped structure on the end of each finger. However, nails begin beneath the surface of the skin in nail beds. Nail beds, or nail roots, provide nails with the nutrients necessary for growth. Constant growth of new cells in nail beds pushes out dead and decaying cells, which in turn stimulates healthy nail growth. The old cells accrue much like sand in the bottom of an ocean, forming a hard base over which new life continues. Old nail cells become hard and flat upon death. New cells deposit over their surfaces, drawing fuel from tiny blood vessels. Despite continual life activity, nails take a long time to grow. The process of regenerating entire fingernails takes between three and six months.