How does the medulla contribute to the hair structure?

The medulla is the innermost layer of the hair structure, and its composition is notable for being made up of round cells. This characteristic is significant because the medulla may contain air spaces that contribute to the overall lightweight nature of hair and impact its flexibility and texture. The presence of these round cells helps distinguish the medulla from the other layers of hair, such as the cortex and cuticle. While the outer layer serves to protect the hair, and the cortex gives the hair its strength and color, the medulla specifically serves as a central core that may affect the hair's physical properties. Thus, the composition of round cells is a defining feature that highlights the role of the medulla in hair structure.