Which part of the hair is responsible for its strength and elasticity?

The cortex is the main part of the hair responsible for its strength and elasticity. It is located beneath the cuticle and is made up of long chains of protein, primarily keratin. The structure of the cortex gives hair its tensile strength, allowing it to withstand various stresses without breaking. Additionally, the cortex contains moisture and pigments, which contribute to the hair's elasticity and color.

The cuticle, while important for protecting the hair, primarily serves as a barrier and does not contribute to the hair's pliability or strength. The medulla, a central core found in some types of hair, is often absent in finer hair types and has less significance in influencing strength and elasticity. The papilla, found at the base of the hair follicle, is a structure that nourishes hair growth but does not directly affect the strength or elasticity of the hair shafts themselves.