7. Skin and Nails

The skin is the largest organ of the body. Enclosing the other tissues it acts as a protective barrier that maintains a stable internal chemical environment. The plantar skin of the foot, as well, provides protection from the high pressures of weight-bearing. Skin blocks the invasion of infectious organisms. Constriction and dilation of blood vessels in the skin and the sweat mechanism are important factors in the regulation of body temperature. The skin provides a large sensory interface with the external world through which varied information is input to the brain, including temperature, pressure, pain, pleasure, and position.