The heaviest part of the human body is the skin. It weighs an average of 24 pounds and accounts for approximately 16 percent of a person's weight, depending on the person's size. The skin is also the largest organ in the human body.
The general purpose of skin is to protect internal organs from dehydration, physical assaults, micro-organisms and radiation. One human leg, which includes numerous structures from many other bodily systems, accounts for around 10 percent of a person's body mass. At an average of 3.4 pounds, the heaviest internal organ is the liver; the second heaviest is the brain, which weighs around 2.8 pounds.