What part of the hair is enclosed within the follicle beneath the skin?

The hair root is the portion of the hair that is enclosed within the follicle beneath the skin. It is located deep within the skin and includes the hair that is not visible externally. The hair root is instrumental in anchoring the hair to the scalp and plays a crucial role in the growth of the hair.

Within the hair follicle, the hair root is surrounded by dermal papilla, which provides blood supply and nutrients essential for hair growth. The root is also involved in the formation of the hair, with cells in the root dividing and producing the hair shaft that emerges from the skin.

While the hair bulb is the swollen base of the root from which the hair grows, it is not the entirety of the portion contained within the follicle; it is a specific part of the root. The hair shaft refers to the visible part of the hair above the skin's surface, while the hair cuticle is the outer protective layer of the hair strand. Thus, the hair root, as the complete structure enclosed within the follicle, is the correct answer.