What structure helps in the formation of keratin in hair strands?

The structure responsible for the formation of keratin in hair strands is the hair follicle itself, specifically the keratinocytes that are found within the follicle. While melanocytes are involved in the pigmentation of hair, they do not contribute directly to the formation of keratin. Keratin, a key structural protein in hair, is produced by keratinocytes located in the hair bulb at the base of the follicle.

The dermal papillae, found at the base of the hair follicle, play a crucial role in supporting hair growth by supplying essential nutrients and signaling for hair follicle development, but they do not produce keratin themselves. The arrector pili muscle is responsible for causing hair to stand upright in response to cold or fear, and sebaceous glands secrete sebum to lubricate hair, neither of which are involved in keratin production. Thus, while melanocytes are essential for hair color, they are not the key cells that produce keratin within hair strands.