What are the three primary layers of the hair strand?

The three primary layers of the hair strand are the cuticle, cortex, and medulla. The cuticle is the outermost layer, composed of overlapping, scale-like cells that protect the inner layers and contribute to the hair's shine and smoothness. The cortex, which is the middle layer, makes up the bulk of the hair shaft and contains fibrous proteins and the pigment that gives hair its color. The medulla is the innermost layer, which may not be present in all hair types, and it consists of a soft, spongy substance that plays a role in the overall structure of the hair.

Understanding these layers is essential for various cosmetology practices, such as hair coloring and treatments, as they each contribute differently to the hair's health, strength, and appearance. The cuticle protects the hair from external damage, the cortex provides strength and color, and the medulla, when present, can affect the hair's texture and manageability.