Which component in the hair structure contains keratin and melanin?

The cortex is the correct answer as it is the middle layer of the hair structure, primarily composed of long chains of keratin, which provide strength and elasticity to the hair. Additionally, the cortex is where melanin, the pigment responsible for hair color, is found. This layer significantly influences the overall appearance and quality of the hair, including its texture and color intensity.

The cuticle, being the outermost layer, primarily protects the hair shaft but does not contain melanin, making it important for protecting the inner structures rather than contributing to hair color. The medulla is a central core found in some hair types, but it is either absent or not significantly influential in terms of color and structure in finer hair types. Lastly, a foliole is not a component of hair structure and may refer to other biological structures, further supporting that the cortex is indeed where both keratin and melanin are contained in the hair.