Why do our fingers wrinkle underwater?

wrinkles

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With the incidence of the Coronavirus, people’s priorities have shifted, securing handwashing the top spot. Handwashing has been around for a long time, but the handwashing routine to be safe from the Coronavirus is extensive and tiresome. One might notice, after a long session of washing that their fingers appear ‘wrinkly’. Another instance where wrinkly fingers make an appearance is during long showers.

This wrinkling of the fingers primarily occurs when our hands are underwater for a considerably long time. It is a rather eerie anomaly which seemingly does not have a reason – or does it?

 

How are wrinkly fingers formed?

The outer layer of our skin, called the EPIDERMIS, is made up of cells called KERATINOCYTES. Since every cell in our body has a specific function to do, the keratinocytes are supposed to be strong, and therefore, have KERATIN in them. Keratin is a protein with tensile strength which makes up the ‘skeleton’ of the keratinocytes. Keratin is most abundantly found in the STRATUM CORNEUM, which is the outer layer of the epidermis. Anatomically, the stratum corneum is like an alternating band of live and dead cells; this ratio of live to dead cells decreases as one goes lower in the layers of the epidermis.

raise hand

Keratin is HYDROPHILIC, which means it is water-loving. Hence, in conditions with an abundance of water, the skin takes in the water, which passes into the keratinocytes, causing keratin to swell up. Since the lower layers of the epidermis are not affected much by this hydration, the upper layers (i.e., the stratum corneum) ‘bunched up’, giving the fingers a wrinkly appearance.

While one might think this is due to excessive hydration, it is not. As the water evaporates, the skin becomes exceedingly dry. Since the skin requires hydration, using a moisturizing lotion can reverse this process and rehydrate the skin.

Scientists initially thought that the wrinkling of the fingers is a purely physiological reaction, occurring due to OSMOSIS – the passage of water through a semi-permeable membrane (in this case, the epidermis) from a region of high concentration to that of a low concentration. Yet, it was observed that this phenomenon is not noticed in individuals with nerve damage – indicating that it has something to do with the nervous system.

hand wrinkles

It was later deduced that this phenomenon is an INVOLUNTARY (i.e., out of the control of the conscious brain). This is commissioned by the AUTONOMIC NERVOUS SYSTEM, by VASOCONSTRICTION – a process by which the blood vessels below the skin shrink. Vasoconstriction allows veins and capillaries to thin in size due to less blood flow. This allows wrinkling of the skin, which also explains why people with nerve damage are unable to experience this – since their nervous system is never able to transmit the signal that induces vasoconstriction.

Why does this occur?

Once the hypothesis of the nervous system has a direct role in the wrinkling of fingers was established, it was widely accepted that there must be an ulterior motive for this – something that goes beyond the availability of water and the reactions of our cells to it.

It was soon proposed that wrinkly fingers were an evolutionary advantage – it improves our GRIP underwater. While underwater, the conditions around are wet and possibly, slippery, thus making the task of grabbing something underwater difficult. So, the appearance of wrinkles aids in holding things underwater since it provides a more precise grip.

An analogy accepted worldwide is with the type of tyres – while smooth tyres are often used during races such as the Formula – 1 car races, treaded tyres are proven to be most effective in rain.

tyres
tyre

Even in the case of our feet, some extent of wrinkling is observed. While not much study has been conducted on why our toes need to wrinkle, one can assume that it helps in running barefoot on wet surfaces as it might reduce the chances of the person tripping.

wrinkled leg

How to prevent this?

While wrinkling of the skin poses no direct threat to a person, there is a simple way to prevent this. If someone must – perhaps for a reason – keep their hands immersed in water for a considerable amount of time and does not desire wrinkling, the addition of salt works. Due to the presence of salt in the water, the chances (or even the extent) of osmosis drastically reduces. Chances are, the salt concentration in the water is more than that of salt in the skin – so, salt from the skin enters the surrounding water, thus preventing wrinkling.

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