The integumentary system consists of the skin, hair, nails, and cutaneous glands.

The skin, or integument, is the largest of the body organs. It includes two distinct tissue layers—the superficial layer, called the epidermis, and a deeper layer, called the dermis. A third layer, the hypodermis (sometimes called subcutaneous tissue), is not part of the skin, but serves to anchor the skin to underlying bone and muscle tissue.The skin provides a barrier against microorganisms, water, solar radiation, and others. Upon exposure to UV radiation, the skin synthesizes an inactive form of vitamin D. The skin is the most extensive sense organ and is important in thermoregulation.