What is the cortex in the structure of hair?

The cortex is indeed the middle layer of the hair structure, and it plays a crucial role in determining the hair's strength, color, and texture. This layer is composed of elongated cells that contain keratin, which is a fibrous protein that provides resilience and durability to the hair strand. The arrangement and structure of these elongated cells allow for the hair to have its characteristic flexibility and elasticity.

Furthermore, the cortex is where the melanin (pigment) is found, which affects the hair's natural color. Changes in the cortex can also alter the hair color through the process of hair coloring. Unlike the outermost protective layer, which is the cuticle, the cortex is where most of the hair's properties are derived from, making it essential in both the aesthetic and functional aspects of hair. This understanding helps in effectively applying hair color and maintaining hair health.