Skin has many functions, some of the most important ones including: serving as a barrier to pathogens, providing insulation while allowing temperature regulation, facilitating our sense of touch, and minimizing water loss.

Skin is a primarily layered structure, with the lower dermis containing hair follicles, glands, nerves, and blood vessels. The epidermis is made up of mitotic cells that die as they get too far away for nutrients to diffuse from the dermal blood vessels. Their cytoplasm becomes replaced with keratin, which is responsible for skin’s barrier function. The outer layers are continuously sloughed off and replaced from below.