The skinny on skin

Here are some skin facts you can use to impress your friends and family:

• Skin is your heaviest organ. It accounts for about 15 percent of your body weight. That means that the skin of a 400-pound sumo wrestler can weigh in at as much as 60 pounds! The skin of an average adult woman weighs about 20 pounds.
• The thickness of the average epidermis varies from 0.5 millimeters on your eyelids to 4.0 millimeters or more on the palms of your hands and the soles of your feet.
• You produce a totally new epidermis about every 30 days!
• Most of the dust in your classroom or bedroom is made of tiny fragments of human skin. In just one minute, 30,000 to 40,000 skin cells fall unseen from the surface of your body. That means you lose around 15 million or so skin cells in one year. (Imagine how dusty it must be in that sumo wrestler’s bedroom!)
• Your dermis is several times thicker than the epidermis and is particularly thick on the upper back. Our thick upper back may have protected us from sabertoothed tigers when we walked on all fours. On second thought, I doubt it.
• “Goosebumps” come from tiny muscles called erector pili. These muscles attach to each of our hairs and make them stand at attention when we’re cold or afraid. We can see this phenomenon on a frightened cat whose fur stands on end. It’s meant to make kitty look bigger and scarier to other animals. And when we had more body hair during the Stone Age, it probably did the same for us.
• You have about 3 to 5 million hairs on your body.
• Your nails grow faster in warmer weather. They grow at a rate of 0.5 to 1.2 millimeters per day, with fingernails growing faster than toenails.