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My cat was licking my arm with his sandpaper like tongue. It hurt and the area he was licking was slightly smarting afterwards. However, when he licks the palm of my hand the feeling is rather ticklish and results in no pain during or after.

We can pick up sharp, prickly, abrasive objects with our hands (palms/fingers) and even rub against them and have little to no damage incurred. However, if we do the same with say the back of our hand we are more likely to be injured.

I thought maybe the skin is thicker in our palms and that is resulting in our palms being more resilient. But, our palms are so sensitive to touch that it makes me think the skin is thinner to allow the nerves closer access to our environment.

  • Why is there such a stark difference in different areas of skin on our body when it comes to feeling pain and being susceptible to injury from scrapes, bruises, cuts, etc?
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    $\begingroup$ Sensitivity to touch depends on the density of mechanoreceptors. $\endgroup$
    – blep
    Commented Jun 28, 2013 at 1:04
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    $\begingroup$ @WYSIWYG do you want to post that as a more detailed answer so I can accept and close this? $\endgroup$
    – kittycat
    Commented Jul 11, 2013 at 21:58

2 Answers 2

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As dd3 said the density of mechanoreceptors dictates skin sensitivity to touch (also look at penfield map. It is a nice illustration of how different senses are mapped to the brain and to what extent each region is sensitive to stimulus). Skin thickness is also different in different regions. This article says that Dikkopf1 (a Wnt pathway antagonist) controls skin thickness.

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There are different receptors and different forces at play here. Skin thickness depends primarily on frictional forces and is determined by the thickness of the epidermis, which is made up of 5 layers of keratinocytes:

  • Stratum basale
  • Stratum spinosum
  • Stratum granulosum
  • Stratum lucidum
  • Stratum corneum

The areas that are subjected to high frictional forces have the thickest epidermal layers, such as palmar surfaces of the hands vs the dorsal aspect of the hand (the back of the hand)which is significantly thinner.

The actual thickness of the skin doesn't always correlate with how tactile or painful stimuli are perceived. The receptors can be very sensitive even where stratum corneum is the thickest and vice versa.

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  • $\begingroup$ Your links are for specific epidermal layers vs providing adequate citations for the claims you make throughout. Please edit. $\endgroup$ Commented Jan 12, 2022 at 14:53

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