How many times this summer have you wondered why, after swimming in the water all afternoon, you came out of the sea or the swimming pool looking like a sultana.
This is how we often ironically refer to the texture that skin takes in water. In fact, it does not have to be hot and there is no need to look for a solution to achieve it, it is enough to take a shower a little longer than usual so that our body seems to shrink.
When we think about the notion of body, it is often the body that helps us define it. After all, it is the most visible part of the body. For example, we see the skin wrinkle as it ages or become “deformed” when pinched. But why does it wrinkle when wet? This question has tormented scientists for centuries.
We often forget that the skin is the largest organ, and it is the first thing we should consider when wondering about it. As astonishing as it is strange, this organ covers all the others. Its main function is to protect you from the outside world, sunlight, harsh chemicals, germs or cold. It does this by keeping water and oxygen inside the body. It is all this that makes the sense of touch possible.
In search of the nervous system
Among the doubts, many have always considered that this reaction was due to the absorption of water through the skin. Yet in the 1930s, it was discovered that in people with nerve damage to their fingers, no wrinkles appeared when they bathed. So they realized that wrinkled fingers couldn’t just be due to water absorption. There was something else…
Guy K. German, biomedical researcher and associate professor of biomedical engineering at Binghamton University (New York), responds in an article for Discoverclarifying everything that science has been able to discover since then until now.
“To explain what’s happening, you first need to know a little about the autonomic nervous system, the involuntary part of the body’s functioning. Functions such as breathing, blinking, pumping of the heart or movement of the pupils occur without us seeming to consciously control them, precisely thanks to this system,” explains the expert.
It also automatically controls the expansion and contraction of blood vessels. And it is on this last point that we must concentrate in the present case. “Think about how your skin can turn red on its own when it’s hot or when you exercise,” German reminds.
When the skin comes into contact with water for more than a few minutes, the sweat ducts in this organ open, and then….
It is this contraction of blood vessels that is also the cause of skin wrinkles after a long bath. “When the skin is in contact with water for more than a few minutes, the sweat ducts in this organ open, allowing water to flow through the skin tissue.” Indeed, we were never mistaken in thinking that water absorption was one of the main reasons for this phenomenon.
But it does not stop there. “This water added to our internal body reduces the proportion of salt found there. The nerve fibers then send a message to the brain that salt levels are decreasing and the autonomic nervous system responds by constricting the blood vessels.
So when the blood vessels contract, the overall volume of the skin is reduced, causing it to fold in on itself. If we return to this popular reference to the sultana, we quickly understand that we lose more volume than surface area.
In addition, the constriction of the blood vessels also causes the skin to become pale: this is the opposite of what happens when the skin turns red when entering a very hot bath, because in this case the blood vessels dilate . But of course, if your nerves have been damaged in some way, the blood vessels may never get the message, so the wrinkles never appear, even if you soak for a long time.
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