What is biologically happening when our skin gets pruned after being in water for too long?
In: Biology
Your body is realizing that things will be slippery. This change occurs to give you a better grip. The same is also true with your feet and toes. I’m sure someone else can go into more detail that I feel comfortable and I’m sure theres more to it than that.
I answered this a while back. Here is my comment:
There have been arguments that pruning enhances gripping, which makes it evolutionarily valuable because when you’re drowning or have been for a while at sea, you’d wanna be able to grab something to hold on to or to get out. However.. A study showed that not to be the case, and showed the grippiness doesn’t change after fingertips get pruny, but this remains controversial as it has been shown that it does enhance grip in some other works (we can get into some comparative analysis of the studies to deduce our conclusion, but that’s too much for ELI5). Now let’s talk mechanisms. Two main hypotheses exist for how wrinkling happens.
1) being in water for a while causes the top or outermost layer of the skin to swell due to osmosis (water flows in) and while the bottom layers don’t change size, this causes wrinkling.
2) a lower layer in the skin actually shrinks, causing the top layer to be too big for it and therefore wrinkles. This shrinking would be due to a physiological response to cold or to water, where the body reduces blood flow to the fingertips and toes to reduce heat loss. Blood vasculature in those regions actually make up a significant volume and when it’s reduces, shrinkage happens in the tissue.
A quite recent study wanted to understand this. So they did some research on both mechanisms and found neither to be quite sufficient in explaining the amount of wrinkling you observe when submerged in water for a while. They now, based on mathematical modeling, believe there is no dominant mechanism (we already know both happen, we just don’t know which is the main reason). They think both contribute almost equally, as even very small low layer shrinkage and top layer swelling can synergistically cause a large amount of wrinkling. So basically.. Both mechanisms are true.
Hope I explained it well, let me know if you have questions. Here is the last paper for your reference, https://www.ncbi.nlm.nih.gov/m/pubmed/27913950/
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