Which part of the hair is rounded and club-shaped at the end of the hair root?

The hair bulb is the area of the hair that is rounded and club-shaped at the end of the hair root. This structure is crucial as it houses the hair papilla, which contains blood vessels that provide the necessary nutrients for hair growth. The bulb is responsible for producing new hair cells, which fill with keratin and push up through the follicle to form the visible hair shaft.

The other options do not fit the description of being rounded and club-shaped. The hair shaft refers to the visible part of the hair that extends above the scalp, while the cuticle is the outer layer of the hair that protects the inner structure. The follicle, on the other hand, is the sheath of cells and tissue that surrounds the hair root, but it is not club-shaped like the bulb. Understanding the functions and characteristics of these different parts aids in grasping how hair grows and the overall anatomy of hair.