Both terminal and vellus hair growth arises from what?

The correct answer is that both terminal and vellus hair growth arises from the hair follicle. Hair follicles are specialized structures located within the skin that play a crucial role in hair development and growth. They are responsible for producing and nurturing both types of hair: terminal hair, which is thicker, longer, and often pigmented (such as scalp and body hair), and vellus hair, which is fine, short, and usually unpigmented (like the soft hair on the face).

The hair follicle contains cells that continuously divide and differentiate to form the hair shaft, as well as the surrounding structures that support hair growth. The health and function of the hair follicle are essential for maintaining an appropriate balance of hair types on the body.

While the other options relate to components of the skin or hair structure, they do not directly produce hair. The skin surface is where hair emerges but does not contribute to its growth, the keratin layer is part of the skin's protective barrier but not involved in hair production, and the hair matrix is specifically involved in hair growth but is contained within the hair follicle itself. Hence, the hair follicle is the key structure responsible for initiating and sustaining the growth of both terminal and vellus hair.