Which part of the hair is primarily responsible for hair growth?

The hair follicle is the part of the hair primarily responsible for hair growth. It is a specialized structure located beneath the surface of the skin and is embedded in the dermis layer. The follicle is where the hair cells divide and grow, eventually pushing the older cells up and out, which forms the visible strand of hair.

Within the follicle, a small bulb called the hair bulb contains rapidly dividing cells, called keratinocytes, that produce keratin, the protein that makes up the hair shaft. Additionally, blood vessels and nerves surrounding the follicle supply essential nutrients and signals that support hair growth and health.

The other components mentioned, such as the cuticle, dermis, and medulla, have different roles in the structure and appearance of hair but are not directly involved in the growth process. The cuticle is the outer protective layer of the hair shaft, while the medulla is the innermost layer that may or may not be present in finer hair types. The dermis is a layer of skin that supports the follicles but does not produce hair itself. Thus, the hair follicle is the key structure facilitating hair growth and development.