Why Do Fingers and Toes Become Wrinkled in Water?
When you spend an extensive period in water, you may notice your fingers and toes becoming wrinkled. It may seem like a simple and somewhat odd occurrence, but this phenomenon is actually a result of a complex physiological response designed to improve grip in wet conditions.
The Science Behind Wrinkled Fingers and Toes
Finger and toe wrinkling is caused by the constriction of blood vessels in the skin, which is mediated by the autonomic nervous system. When the skin absorbs water and swells, the body triggers a response from the sympathetic nervous system, which constricts the blood vessels in the fingers and toes.
Water Absorption and Nerve Response
When fingers and toes are submerged in water for an extended period, the outer layer of skin, the stratum corneum, absorbs water and swells. This swelling is then detected by the body, leading to a response from the autonomic nervous system. Specifically, the sympathetic nervous system constricts the blood vessels, reducing the volume of the underlying tissue while the outer layer of skin retains its size. This differential results in the wrinkling effect.
Functionality and Adaptation
The purpose of this wrinkling is thought to enhance grip on wet surfaces, making it easier for our ancestors to handle objects in rain or water. This adaptation is an example of how our bodies adapt to environmental conditions, demonstrating a blend of anatomical and evolutionary responses.
Is Wrinkling a Reflex or a Biochemical Reaction?
The wrinkling response is not a simple reflex or the result of osmosis. Surprisingly, studies have shown that cutting certain nerves to the fingers can eliminate the wrinkling response, indicating that it is a neural response. This suggests that the wrinkling of fingers is a sign of an intact nervous system.
Researchers hypothesize that the wrinkling is a result of a biochemical reaction rather than osmosis. Some argue that this reaction serves a frictional purpose, helping to channel water away from the skin, much like the grooves on a car tire do for the water on the road. This helps primates, including humans, maintain a tighter and more secure grip on wet surfaces.
Origins and Evolutionary Considerations
The scientific community consensus is that the wrinkle response is not a simple reflex but a neural response. However, whether and how this wet-wrinkling response may have evolved and if it even represents an adaptation remains a contentious and continuous debate.
Researchers have found evidence that wrinkled fingers indeed act as "rain treads," channeling water away from the fingers and toes during wet conditions. The inverted pattern of the wrinkles is thought to mimic a drainage system, with ridges and channels functioning similarly to how a river and its tributaries move water away from a landscape. This can be understood as a tiny manual river drainage system, optimized for better grip in both wet and dry conditions.
Practical Applications and Further Research
While the exact reason for wrinkles may be unclear, researchers are exploring potential applications and further studies. For instance, the response could be used as a diagnostic tool to determine whether the sympathetic nervous system is functional in patients.
Field tests and further research would involve observing how this response impacts locomotion and grip in real-world scenarios. Researchers suggest that the ideal experiment would involve recruiting parkour experts to showcase their urban acrobatics in both wrinkled and non-wrinkled states, under wet and dry conditions. This would provide more practical insights into the benefits of wrinkled skin for supporting body weight and grip in natural settings.