April 29, 2012 | David F. Coppedge

Why You Are Waterproof

Can you imagine inflating like a water balloon every time you jumped in a swimming pool?  Or what if water leaked out of your skin every time you drank a glass of water?  Your skin forms an impermeable barrier to water, a new study found, because of a unique way certain molecules are arranged.

In “Strange Fat Explains Skin’s Waterproof Properties,” Helen Thomson reported for New Scientist about a study from the Karolinska Institute of Sweden.  There, Lars Norlén shaved arms of volunteers to obtain microscopically thin layers of the outer skin layers.  Studying the waterproof layer at unprecedented resolution, the team was surprised to find alternately-stacked fatty acid molecules.

Normally, fatty acids in cell membranes have two hydrophobic (water-repelling) “tails” and a water-attracting “head.”  In skin, however, the tails are unfolded and point in opposite directions.  This creates water-repelling surfaces on both sides of the layer.    This layer is completely robust, Norlén said:

This uniquely structured fatty layer prevents any water from getting past in either direction – except where the skin layer is modified to form pores. “There’s no water present within this extracellular space,” says Norlén. “It cannot perturb the barrier so it’s completely robust to hydration, which is necessary for the changing environment that we live in.

Thanks to this unique arrangement, we don’t leak and can swim with confidence.  We sweat, of course, but that’s another story; sweat glands are complex pores that emit water as part of our tightly controlled thermoregulatory system.

Your skin is the largest organ of your body.  Thank God He thought of everything.  Enjoy this little-known fact when you take your next swim.


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