How are skin, hair, and nails related?

The integumentary system comprises the organs that form the outermost layer of the body. In humans, the integumentary system consists of skin, hair, and nails, which help protect the rest of the body and maintain homeostasis. The outermost layer of skin (the epidermis) is primarily composed of keratinocytes (cells that contain the protein keratin, which holds water and keeps the skin hydrated), and the topmost part of the epidermis is primarily composed of dead keratinocytes. Hair and nails don’t contain any cells but are instead composed of keratin (and other proteins). Alongside the integumentary system’s functional role, it also can play an important aesthetic role.