Skin

:For alternate meanigns see skin (disambiguation)

Functions

• Protection: an anatomical barrier between the internal and external environment in bodily defense; Langerhans cells in the skin are part of the adaptive immune system
• Sensation: contains a variety of nerve endings that react to heat, cold, touch, pressure, vibration, and tissue injury.
• Heat regulation: The skin contains sebaceous glands and smooth erector pili muscles.
• Storage: acts as a storage centre for lipids and water, as well as a means of synthesis of vitamin D and B by action of UV on certain parts of the skin.
• Excretion: The concentration of urea is 1/130th than that of urine. Excretion by sweating is at most a secondary function to temperature regulation.
• Absorption: Oxygen, nitrogen and carbon dioxide can diffuse into the epidermis in small amounts. In addition, medicine can be administer through the skin, by ointments or by means of adhesive patch, such as the nicotine patch or iontophoresis. The skin is an important site of transport in many other organisms.