Which part of the hair is visible above the surface of the skin?

The hair that is visible above the surface of the skin is known as the hair shaft. The hair shaft is the part that extends outward and is exposed to the external environment. It is primarily made of keratin, a structural protein that provides strength and durability.

Understanding the anatomy of hair helps clarify why the hair shaft is the correct answer. The hair root is located beneath the skin and is responsible for anchoring the hair into the follicle, while the hair follicle is the structure that surrounds the root and secretes the components necessary for hair growth. The hair bulb is found at the base of the hair follicle and contains the living cells that divide and grow to form new hair. Therefore, the visible part of the hair, which is the hair shaft, is distinct from these components that reside below the skin's surface.