What are papillae?

Papillae refer to small, nipple-like projections found in the dermis, which play a crucial role in the structure and function of the skin. They extend into the epidermis and contribute to the formation of fingerprints and patterns on the skin surface. This unique structure enhances the grip, increases surface area for nutrient exchange, and provides tactile sensations by housing nerve endings. Additionally, the papillae contain loops of capillaries that supply nutrients to the epidermis, which is avascular and relies on diffusion for nourishment.

The other options describe different components of the skin but do not accurately define papillae. Fibrous proteins in the skin refer to structural proteins like collagen and elastin, while layers of skin cells pertain to the stratified arrangement of the epidermis. Vascular tissues in the epidermis are not applicable since the epidermis does not contain blood vessels; it receives its blood supply from the underlying dermis. Thus, the definition of papillae as small, nipple-like projections in the dermis is both precise and relevant to understanding skin anatomy and physiology.