In addition, the skin helps keep the internal temperature of the body within normal levels. Glands in the skin release sweat when a person becomes overheated. The sweat evaporates and so cools the body. When a person becomes too cool, the body retains heat by narrowing the blood vessels in the skin. As a result, the flow of blood near the surface of the body decreases, and the body gives off less heat. The skin has many nerve endings that are sensitive to cold and heat, as well as pain, pressure, and touch.
The skin is the largest organ of the human body. If the skin of a 68-kilogram adult male were spread out flat, it would cover about 2 square metres.
This article deals mainly with the skin of human beings. It discusses the structure and colour of the skin and various skin disorders. The last section describes the skin of other animals.