PSI Barbering Practice Exam 2026 - Free Barbering Practice Questions and Study Guide

The innermost layer of the hair is known as the medulla. This central core consists of a soft, spongy substance that may be present in varying degrees across different types of hair. In some hair types, the medulla may be absent altogether, while in others, it is fully developed.

Understanding the structure of hair involves recognizing the roles of the other layers as well. The cuticle is the outermost protective layer that helps shield the hair from damage and environmental effects. The cortex lies beneath the cuticle and is responsible for the hair's strength, color, and texture due to its composition of fibrous proteins and melanin. Finally, the hair shaft refers to the entire length of hair that extends above the scalp, which encompasses both the cuticle and cortex.

This knowledge of the hair structure is essential in practices such as cutting, coloring, and treating hair, enabling barbers and stylists to make informed decisions tailored to individual hair types.