Fingernails and toenails are made from skin cells. Structures that are made from skin cells are called skin appendages. Hairs are also skin appendages.
The part that we call the nail is technically known as the “nail plate.” The nail plate is mostly made of a hard substance called keratin. It is about half a millimeter thick and slightly curved.
The nail is firmly attached to the nail bed beneath it. The nail and nail bed separate at the tip of the finger or toe, where the end of the nail sticks out. This allows us to use our nails as tools, for example for scratching. The nails are also an important part of the sense of touch.
The nail is framed by the lateral nail folds on the left and right side of it. The skin bordering the lower end of the nail is called the proximal nail fold. A thin layer of skin, known as the cuticle, grows over the nail there.
How do nails grow?
At the proximal nail fold, the nail is tucked into a pouch in the skin. This area is referred to as the matrix. If you look at a nail, you will see a light half-moon-shaped area shimmering through the nail plate at the base of the nail. This is the visible part of the matrix. It is called the lunula (Latin for “small moon”) because of its shape.
The matrix constantly produces new keratin that gathers at the nail plate and slowly pushes the nail forward, causing it to grow. Fingernails grow at a rate of about 3 millimeters per month. Toenails grow a little slower.
Sources
Aumüller G, Aust G, Conrad A, Engele J, Kirsch J. Duale Reihe Anatomie. Stuttgart: Thieme; 2014.
Moll I. Duale Reihe Dermatologie. Stuttgart: Thieme; 2016.
Wollina U, Nenoff P, Haroske G, Haenssle HA. The Diagnosis and Treatment of Nail Disorders. Dtsch Arztebl Int 2016; 113(29-30): 509-518. [PMC free article: PMC5527843] [PubMed: 27545710]
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