The cuticle of a hair is the outermost layer of the hair (see the diagram below).
To appreciate this in the overall context of the structure of hair, note that, structurally, hairs are threads of fused (i.e. attached together), dead, keratinized cells. They consist of two main parts:
- The hair shaft is the visible part of the hair that protrudes through the skin. It is composed of three layers. The innermost layer is called the medulla and is only present in large thick hairs. The middle layer is called the cortex and outermost layer is called the cuticle.
- The hair root is the part of the hair below the surface of the skin that includes and/or interacts with many other associated structures within the dermis and hypodermis layers of skin.
More about the cuticle of hairs:
The cuticle of a hair extends along its length, i.e. through the hair root as well as the hair shaft. The cuticle of a hair is a thin colourless layer that protects the cortex of the hair.