What structure in the skin or scalp contains the hair root?

The hair follicle is the structure in the skin or scalp that contains the hair root. It is a tubular invagination of the epidermis that surrounds the hair shaft and plays a crucial role in supporting hair growth. Within this follicle, the hair root is anchored and nourished, allowing the hair to grow from its base.

The hair bulb, while it does house the lower part of the hair root and is essential for hair formation, is specifically the enlarged part at the bottom of the hair follicle. The hair shaft is the visible part of the hair that extends above the skin's surface and does not contain the hair root itself. The hair matrix refers to the region at the base of the hair bulb where cells divide and produce hair, but it does not encompass the entire structure of the hair follicle, which is why the hair follicle is identified as the correct answer.