Which part of the hair is primarily composed of keratin?

The hair structure is primarily composed of keratin, a protein that forms the key structural component of hair, skin, and nails. Understanding the roles and compositions of the different layers of hair is crucial.

The cuticle is the outermost layer of the hair shaft, consisting of overlapping flat cells. While it is indeed made of keratin, its primary function is to protect the inner layers of the hair.

The cortex lies beneath the cuticle and constitutes the bulk of the hair's structure. It is rich in fibrous proteins, including keratin, and is responsible for the strength, color, and texture of the hair.

The medulla is the innermost layer of the hair shaft and may or may not be present in all hair types. Though its composition can vary, it is generally made up of a softer keratin.

Since all aspects of the hair structure contain keratin—albeit in different forms and functions—it is accurate to state that keratin is a primary component throughout the cuticle, cortex, and medulla. Therefore, identifying that all parts are made up of keratin clarifies the comprehensive role keratin plays in hair composition.