Your skin is the largest organ of the body.
Yes, your skin is in fact an organ, just like your lungs, heart, and liver. The skin makes a good covering for you, keeping all of the outside stuff out, and the inside stuff in. And you’d probably look pretty scary without it (ever see the Bodies Revealed exhibit?).
But your skin is much more than just a wrapper for your body—it actually has many jobs. Your skin helps regulate your body temperature by either releasing or retaining heat as needed, and it’s also an organ of protection. Your skin also guards your muscles, nerves, and other internal organs from injury, and it defends the body against invading bacteria as well.
Of course, the skin also helps us experience the world. Through our skin we feel the sensations of heat, cold, pain, and pressure (touch). The skin has thousands of sensory nerve fibers specialized just for these purposes.
All of this occurs in an organ that covers nearly 20 square feet, and weighs about 6 pounds.