The inner core of a hair strand is called:

• A. Cortex
• B. Cuticle
• C. Matrix
• D. Medulla

Answer: (D)

The inner core of a hair strand is called the medulla. Hair is built in layers: the medulla at the very center, the cortex surrounding it, and the cuticle on the outside. The medulla is typically made up of loosely packed cells and air spaces, and it isn’t always present in all hair types, especially finer hair. The cortex around it provides most of the hair’s strength and color, while the cuticle forms the protective outer layer with its scale-like cells. The matrix, by contrast, is the part in the hair follicle where hair is produced, not a component of the hair shaft itself. So for the inner core, the correct term is medulla.