Structure and Growth of Fingernails and Toenails

Nails serve several important purposes.

• They help humans function. Nails are basically flat versions of claws that help humans dig, climb, scratch, grab, and more. 
• They guard against injuries. They serve as protective plates that help prevent the fingers and toes from getting cut or scraped during daily activities.
• They enhance the sensation. The fingers and toes contain nerve endings that allow the body to process the volumes of information that it receives every time something is touched—and the nail acts as a counterforce, providing even more sensory input after a person touches something.

Nail Growth

Nails are constantly growing, but their growth rate slows down due to poor circulation and aging. Fingernails grow faster than toenails, at a rate of 3 millimeters per month. It takes six months for a fingernail to grow from the root to the free edge. Toenails grow much more slowly, at just 1 millimeter per month. It takes a toenail 12 to 18 months to grow from root to tip.

Nail Structure

The nail structure is divided into six parts: root, nail bed, nail plate, eponychium, paronychium, and hyponychium. Each of these six components has a specific function, and if a component of the nail structure is disrupted, the nail can look abnormal. 

• Nail root: The root of the nail is also known as the germinal matrix. Its edge appears as a white crescent, known as the lunula. The root portion of this nail lies below the skin, underneath the nail, and extends several millimeters into the finger. It produces most of the volume of the nail and the nail bed.
• Nail bed: The nail bed is also referred to as the sterile matrix. It extends from the edge of the nail root, or lunula, to the hyponychium. The nail bed contains blood vessels, nerves, and melanocytes that produce melanin. As the root grows, the nail streams down along the nail bed and adds material to the underside of the nail to make it thicker. When the nail grows properly, the nail bed is smooth, but if the nail doesn't grow correctly, the nail may split or develop ridges that aren't cosmetically attractive.
• Nail plate: The nail plate is the actual fingernail, and it's made of translucent keratin. The pinkish appearance of the nail comes from the blood vessels that are underneath it. The underside of the nail plate has grooves that run along the length of the nail and help anchor it to the nail bed.
• Eponychium: The eponychium is more commonly known as the cuticle. The cuticle is situated between the skin of the finger and the nail plate. It fuses these structures together and provides a waterproof barrier.
• Perionychium: The paronychium is the skin that overlaps onto the sides of the nail plate, also known as the paronychial edge. The paronychium is the site of hangnails, ingrown nails, and paronychia, a skin infection.
• Hyponychium: The hyponychium is the area between the free edge of the nail plate and the skin of the fingertip. It also provides a waterproof barrier.