The cortex layer of the hair structure is responsible for the hair's which properties?

• A. Strength and elasticity
• B. Color
• C. Surface smoothness
• D. Moisture retention

Answer: (A)

The cortex is the thick, fibrous inner layer of the hair shaft that provides most of its strength and elasticity. Its keratin fibers are arranged in a way that resists pulling forces and can stretch slightly and then spring back, thanks to cross-links between keratin molecules. This gives hair its ability to bend without breaking and to recover its shape after deformation. While pigment in the cortex affects color and the cuticle layer influences surface smoothness and moisture retention, the mechanical properties described—strength and elasticity—come mainly from the cortex.