Final answer:
The cuticle layers protect the cortex of the hair strand, which is a layer of compressed, keratinized cells responsible for hair texture.
Step-by-step explanation:
The cuticle layers protect the cortex, which is the second or middle layer of the hair strand. The hair shaft has three zones: the cuticle (the outermost layer), the cortex (the middle zone), and the medulla (the innermost zone). The cortex is made of compressed, keratinized cells and determines the hair texture, be it straight or curly. The entire structure originates from the hair matrix, which also contains a layer of basal cells that are vital for the growth and development of the hair strand.