Topic 2 Summary
A strand of hair is composed of three layers each with its own unique characteristics and division of labor.
The innermost layer of the hair is the medulla. This layer of hair is often missing in fine hair or light blonde hair. Its purpose is unknown. The middle layer of the hair is the cortex, responsible for giving the hair its elasticity, tenacity, and strength. It is in this layer that pigment, the substance that gives color to the hair, is found. In this layer, chemical changes take place, once the cuticle has been penetrated. The outer layer of the hair is composed of transparent, overlapping scales much like the shingles on a roof. The purpose of this layer is to protect the cortex.