Do you know what your largest organ is? If you guessed the liver, it is the largest internal organ, but your largest organ is your skin! Adults have about 8 pounds of skin that covers about 22 square feet.
Skin is our insulator and our water proofer, but sometimes water can make skin on our fingers and toes wrinkly. Why does that happen?
It’s not a life-or-death matter, but those skin wrinkles do have a function for your body.
In science class you probably learned about osmosis, how fluid moves through cell walls and membranes. People used to think that’s why your fingers and toes wrinkled. Water soaking into the skin puffed parts of it up, making those wrinkles.
But then researchers noticed that it didn’t happen to people with nerve damage to the fingertips or toes. That meant the wrinkling was part of an involuntary (automatic) response of the nervous system.
Pruney fingers and toes are actually caused when blood vessels just below the skin shrink — a process called vasoconstriction. When your nervous system is functioning properly, soaking in water sends a message through the nerves telling those blood vessels to shrink. The loss of blood volume makes the arteries, veins and capillaries skinnier. Then the skin over them collapses into wrinkles.
But Why Does Your Nervous System Want You To Have Wrinkly Surfaces?
Creating temporary wrinkles might have to do with evolutionary advantage. Those wrinkly fingertips might help you grip things better.
If you’ve got some marbles, try picking them up first with dry fingers and then with presoaked, pruney ones. That’s the experiment scientists did to test whether wrinkled fingers gripped better. They did.
As to your toes, they haven’t tested those yet. But when you have to move fast on wet ground, wrinkly toes might have better gripping qualities too. And that might have made a difference to some distant barefooted ancestor fleeing a predator in the rain.
There’s still a lot to learn about the hows and whys of water wrinkling. Does it happen to primates who use their hands the way humans do? And if it’s such an advantage, why don’t they stay wrinkled all the time? And then, when another group of scientists tested the wrinkly finger theory with other objects, they found no improved ability to grip, so the jury is still out.