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

The cortex is the part of the hair structure that is primarily responsible for strength and elasticity. This layer of the hair is made up of long chains of keratin fibers, which provide the hair with its structural integrity. The cortex is also where the color of the hair is determined, as it contains melanin, the pigment that gives hair its natural hues.

The strength of hair comes from the tightly packed keratin proteins within the cortex, which allow the hair to withstand bending and stretching forces. Additionally, the cortex's elasticity enables hair to return to its original shape after being manipulated, allowing it to bend without breaking.

The other parts of the hair structure serve different functions. The cuticle, which is the outermost layer, protects the inner layers of the hair but does not contribute to the strength and elasticity. The medulla, found in the center of thicker hairs, is not present in all hair types and generally does not play a significant role in hair strength or elasticity. The follicle, which is not a part of the hair shaft itself, is the structure in the skin from which hair grows, but it does not provide strength or elasticity to the hair. Thus, the cortex is the key component that ensures the hair remains strong and flexible.