Which layer is the innermost part of the hair?

The medulla is the innermost part of the hair shaft and plays a significant role in the overall structure of hair. It is often described as a soft, spongy core that can vary in thickness and presence among different hair types. The medulla may not be present in all hair strands, particularly in finer hair types, but when it is there, it contributes to the overall strength and flexibility of the hair.

In contrast, the cortex is the middle layer of the hair and is responsible for the hair’s strength, color, and texture. The cuticle, on the other hand, is the outermost layer consisting of overlapping cells that protect the inner layers of the hair. The follicle is not a layer of the hair shaft itself but rather the structure in the skin from which the hair grows, housing the root of the hair. Understanding these distinct structures helps to appreciate how hair is formed and its various characteristics.