Why do our fingers wrinkle in water?

After a long bath your fingertips look like prunes, while the rest of your skin stays smooth. Stranger still: a finger whose nerve has been cut stays completely smooth in the same water, which is why doctors can use wrinkly fingers as a simple nerve test. We open the skin layer by layer: why the old sponge explanation isn’t the whole story, how your nervous system’s "autopilot" squeezes tiny blood vessels, why the fingertip deflates a little and folds into waves, how fingers can wrinkle without any water, why it takes minutes and why only palms and soles. Then: are wrinkles "rain treads" for wet objects, and what did the experiments actually measure? Skin cross-sections and graphs are simplified illustrations. Research hasn’t settled what the wrinkles are for. Chapters 0:00 Prune fingers 0:40 A sponge made of keratin 1:27 A clue from the hospital 2:07 An autopilot in your skin 2:46 A fingertip that deflates 3:38 Why waves? 4:22 Wrinkles without water 4:58 A nerve test 5:32 Minutes, and the way back 6:07 Only palms and soles 6:45 Side effect or tool? 7:13 Rain treads 8:08 The marble test 8:41 The repeat 9:22 Grip force 9:58 The answer Which little secret of your own body should we explain next? Tell us in the comments and subscribe for more discoveries. #Exploriny #Skin #Science