Today’s factismal: Weighing 8 lbs, the human skin is our largest (and most sensitive) organ.
Human skin is a marvel of nature. Not only does it hide all the gooshy bits, it also acts as a sensor system, a shock absorber, a water barrier, a thermostat, and a container. That’s an awful lot to ask of any single organ, but the skin manages it marvelously.
Sensor system: Your skin is chock-full of small sensors that register pressure, stretching, and temperature; there are over a thousand nerve receptors in an average square inch of skin. These mechanoreceptors respond to subtle changes in the environment and act as a sort of early warning system. They are most abundant on your palms and the soles of your feet and least common on your back (that’s part of why the old “bed of nails” trick is possible).
Shock absorber: Lying just under your outer skin (the “epidermis” which literally means “outer skin”) is a thin layer of fat that acts to absorb small shocks; the layer is thickest in your palms and soles for obvious reasons. An equal partner in the shock absorber function is the interlacing of collagen throughout your skin. Thin and stretchy, collagen acts like a net and redistributes strain as you move.
Water barrier and container: Your skin acts like a plastic baggie, keeping the water that’s in you from becoming water outside of you. This reduces the amount of water that we need to drink. As a side benefit, this keeps nasty stuff like bacteria and dirt outside of us, which helps keep us healthy.
Thermostat: There are four million small pores across your skin which release sweat when it is hot, which cools your body via evaporation. On a hot day an adult can lose as much as two liters of water through sweat every hour! Interestingly, strong emotions such as embarrassment can also cause sweating in humans but that sweat is much more restricted than sweating from heat or exercise. Where exercise and heat cause the entire body to sweat, sweat from emotion is typically found just in the palms, soles, and armpits.
Not surprisingly, your skin gets replaced on a regular basis. As the roughly 19 million cells in each square inch of your skin (that’s 60 billion skin cells total for a typical person) get older, they lose water and flatten out. Meanwhile, new skin cells are born at the base of your skin, forming a new layer. As the top cells die, the new cells are exposed creating a continuously self-renewing surface. Every day about 100,000,000 skin cells die and flake off; at that rate, it takes about two years to completely replace your skin.
And not surprisingly , when something that complicated gets replaced so often, things can go wrong. In addition to the normal signs of aging in skin, such as crow’s feet, sagging, and single party ticket voting, skin cells can become cancerous. A recent study has found that nearly a quarter of the skin cells in older people show mutations that can signal the start of skin cancer. Though skin cancer is easily treated when caught early, when allowed to progress it can become deadly fairly quickly.
So what can you do about it? First and foremost, always wear sunscreen. Experts estimate that you are twice as likely to develop skin cancer if you’ve had as few as five sunburns. In addition to protecting you from skin cancer, sunscreen also helps prevent crow’s feet and sagging in skin, which helps keep you looking younger for longer. The other thing that you can do to help prevent skin cancer is to play video games. No, seriously! Cancer researchers in Great Britain have invented a game called Reverse the Odds. When you play their game you not only have fun with video games, you are also analyzing (excuse me – analysing) cancer data and helping them to search for a cure. To learn more, head over to: