The main function of the toenails is to provide protection to the tips of the toes. By design, the nail unit can also act to enhance sensation. The nail unit is composed of the nail plate, nail fold, lunula, cuticle and hyponychium.
Nail plate: known to most as simply the “nail”, the nail plate is composed of a translucent protein called keratin. The nail plate does not grow itself, the activity comes from the nail root. The nail plate is porous to water and the water content is directly related to it’s brittleness or hardness. The calcium content of the nail plate is less than 0.5%. The nail plate does not contain any blood vessels or nerves.
Matrix: The nail root and the sole structure responsible for the formation and growth of the nail plate. The nail root sits beneath the proximal nail fold. The matrix produces the keratin cells which form the nail plate. The matrix determines the shape and thickness of the nail plate.
Cuticle: also known as the eponychium, is formed from cells from the proximal nail fold, the cuticle attaches to the nail plate acting as a natural seal to protect the proximal nail fold from microbial invasion. The cuticle should be left undisturbed. When the seal is broken, the cuticle and/or the proximal nail fold can become inflamed or infected.
Proximal nail fold: covers about 1/5th of the base of the nail. The proximal nail fold adheres to the newly formed portion of the nail plate and those cells eventually become part of the cuticle. The nail fold helps to protect the nail matrix.
Lunula: a crescent-shaped white zone at the base of the nail which represents the furthest extension of the nail root.
Hyponychium: a thickened skin below the free edge of the nail plate. The hyponychium represents the junction of the nail bed and the epidermis.
Nail bed: extends from the lunula to the hyponychium and supports the nail plate in it’s contour. It does not assist with the growth of the nail plate, but functions to allow the nail plate to move, while still being firmly attached. The nail bed contain blood vessels and nerves.
Free edge: the tip of the nail plate that is not attached to the nail bed or the skin.
Toenails grow more slowly than fingernails, perhaps due to lower temperatures and a slower rate of blood flow. The great toenail grows at a rate of about 1 mm per month and peaks during the second decade of life. Nails tend to grow more quickly in the summer and more slowly in the winter or in colder climates. Illness like the mumps or measles, or malignancy can slow nail growth. Starvation, oral steroids, methotrexate or other chemotherapy can also slow growth. The nails may grow faster in pregnancy in diseases such as psoriasis or after trauma.
More on Disorders of toenails.
last updated 4/22/15
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