The skin is the heaviest organ in the body, and is an organ of heat regulation as well as one of protection. It has two parts – the horny outer epidermis and the soft inner dermis, in which are embedded hair pellicles and sebaceous and sweat glands. It weighs 2.72 kilograms. The skin is the largest organ of the human body as well. If the skin of a 68 kilogram adult male were spread out flat, it would cover about 1.8 square meters.

Just one square inch of skin, about twice the area of your thumbnail and no thicker than two coins, contains about 645 sweat glands, 77 feet of nerves and 1,000 nerve endings, 65 hair follicles, 75 sebaceous (oil-producing) glands and 19 feet of blood vessels. A good-sized man sheds about 600,000 particles of skin every hour, which amounts to 680 grams each year. By age of 70, one will have lost nearly 47.5 kilograms of skin – equal to about two-thirds of one’s entire body weight.

But, the largest internal organ is the liver. It is also the heaviest organ, with an average of 1.6 kilograms (3.5 pounds).