To know more about cuticle hair

Most people know the cuticle is the part of the hair, but few people know what the hair is actually made up of.
For human hair, generally speaking, the hair consists of three layers, the outer layer is the cuticle, the middle layer is the cortex, and the inner layer is the medulla.

The cuticle is the most outer layer of the hair, so it acts the first line of defense against all forms of damage.
The cuticle also acts the mechanical strength of the hair, so the hair with intact cuticles are much stronger than the hair with damaged cuticles.
The cuticles run in direction. For one single hair, all its cuticles go in the same direction. For hair bundles, once one hair is upside down, the cuticles from this hair will fight with others, so the hair will get tangled, this is also why we always said virgin hair has the cuticles run in the same direction.
Further, the cuticle also represents the water content.
If the cuticles are healthy, intact and organized closely, the hair looks healthy, strong, and naturally shining.

The cortex is the main part of the hair. The main color pigments are placed in this layer.

The medulla is the most inner layer of the hair shaft. It is nearly invisible, but it is the marrow of the hair. The scientists are still working on its exact function.

Please take a look at the following diagram of the hair shaft.

cuticle of hair