Composed mainly of keratin, it has three morphological regions—the cuticle, medulla, and cortex.
These regions are illustrated in Figure 1 with some of the basic structures found in them. The
illustration is a diagram used to emphasize structural features discussed in this guide. Certain
structures may be omitted, and others enhanced for illustrative purposes.
The medulla is in the center of the hair. Its diameter varies according to the thickness of the hair. In thick hair it is like a canal and gives the hair its stiffness. In fine hair it is only partly there or completely missing.