Grades K–2 · Organisms
How do hair and nails keep getting longer?
Hair does not grow from its tip. Living cells deep in a tiny pocket in the skin make new hair material. As more material is added, the hair strand moves outward. The pocket is called a follicle.
In the diagramHair and nails grow from living cells at a baseNew cells add material at the highlighted baseHair follicleNail baseClipped tips do not contain the growth-making cells.
Nails also have a growing area near their base. New cells are made there and become packed with a tough material called keratin. They harden and become part of the nail moving toward the fingertip. The exposed hair strand and nail are made of nonliving material.
That is why clipping a nail tip or cutting a hair strand does not cut through the living growth-making cells. Hair follicles also go through growing and resting stages, so every hair is not growing at once. The picture enlarges the two bases to show where new material comes from.
About this explanation
Starting knowledge: Know skin contains living cells.
Sources
- OpenStax, Anatomy and Physiology 2e — Accessory Structures of the Skin