Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
A callus is a thickened and hardened area of skin that forms as a response to repeated friction, pressure, or other irritation. This protective layer helps prevent underlying skin from damage or injury.
The process by which cells become filled with keratin protein, harden, and die, contributing to the formation of structures like hair, nails, and the outer layer of skin.
The layer of skin beneath the epidermis that contains nerve endings, sweat glands, oil glands, and blood vessels.
Friction Blister: A small fluid-filled bubble on the skin that forms due to friction against an irritant, often preceding callus formation if the irritation continues