The major organ of the integumentary system, and the largest organ in the body, is the skin. The primary function of the skin is to help the body maintain homeostasis with its environment. The integumentary system is composed of the skin, hair, nails and exocrine glands.
To maintain homeostasis, the skin protects the body's internal living tissues and organs from invasion by infectious organisms. The skin also regulates fluid balance in the body to protect against dehydration and helps the body maintain a stable temperature. In addition, the skin stores water and some types of adipose tissue. The skin also serves as a receptor for touch, pain and heat.