Utah Cosmetology and Barbering Practice Exam 2025 - Free Cosmetology and Barbering Practice Questions and Study Guide

The cortex is the layer of the hair that is primarily affected by chemical processes such as coloring and perming. The cortex is the thickest layer of the hair shaft, located beneath the cuticle, and contains long, coiled chains of keratin that provide the hair with strength, elasticity, and color. When chemical treatments are applied, they penetrate the cuticle and alter the structure of the cortex, allowing for changes in color and texture of the hair.

In the case of hair coloring, the chemicals penetrate to the cortex to deposit color pigments or lighten the natural pigments. With perming, the chemical solutions break and reform the disulfide bonds within the cortex, enabling the hair to take on a new shape or curl pattern. Therefore, the cortex's structure and composition make it susceptible to the effects of various hair treatments.

The other layers mentioned serve different purposes. The cuticle, for instance, acts as a protective layer over the cortex, while the medulla, which is often absent in finer hair types, is the innermost layer and does not contribute significantly to the hair's overall strength or appearance in the context of cosmetic treatments. The sebaceous layer is not a hair layer but rather refers to the skin's glands that produce se