What Is Skin: Skin Health

Content provided by the Faculty of the Harvard Medical School

What is skin?

The skin is the body's largest organ, weighing about nine pounds. It carries out a number of functions that help maintain health. Skin is a complex fabric of tissues working together to form a basic control system (see Figure 1). Skin helps control your body temperature by sweating and dilating its blood vessels to cool you down. When you're cold, those blood vessels constrict to conserve heat deep inside your body.

Figure 1: More than skin deep Structures Functions Protective barrier Temperature control Vitamin D manufacture Fights infection Sensory organ Skin is more than just a cosmetic covering for the body. Its blood vessels and sweat glands regulate body temperature. Its immune cells ward off infection. Tiny nerve cells detect pressure and temperature, and other skin cells manufacture vitamin D.

The skin is also a sensory organ. Nerve endings on its surface pick up and relay information about the surrounding environment to your brain. Your brain then translates these nerve impulses into the sensations of heat and cold, as well as touch, pressure, and pain.

In addition, the skin helps ward off infection by way of its Langerhans cells, part of the immune system that fights off foreign invaders such as bacteria and viruses. The skin is also a manufacturing plant, using the sun's energy to make vitamin D, essential to making bones strong.

Last updated:	July 20, 2007