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I found out some interesting facts while studying our lips:

  • They are covered in glabrous skin, while most of the skin surface is hairy;
  • The outermost layer (stratum corneum) of the skin is far thinner than on any other part of our body;
  • They lack pigmentation (melanin);
  • Their pink colour is due to underlying capillaries.
  • Their only source of moisture is our saliva. They lack sebaceous gland;

What is the reason behind this specialization of our lips?

Why is it not covered with the thicker skin type found elsewhere on the body? The lips are not more sensitive than the fingertips for example (see figures below), i.e., the pressure thresholds are similar (upper graph) and the two-point discrimination thresholds as well (lower graph).

enter image description here
Source: Dreamviews

enter image description here
Source: Institute Balseiro

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  • $\begingroup$ I edited your question and removed my answer. You're right! Sensitivities are similar on fingertips and lips! That is interesting... I edited your question. +1 Feel free to roll back if you don't like the edits. $\endgroup$ – AliceD Aug 28 '15 at 13:49
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    $\begingroup$ No no there is nothing to troll . I respect you mam . Thanks for your support :) $\endgroup$ – Chloritone_360 Aug 28 '15 at 13:53
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    $\begingroup$ LOL - That was a typo :) I meant "Feel free to roll back" :-) $\endgroup$ – AliceD Aug 28 '15 at 13:55
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    $\begingroup$ @Pi5 you need not address people as Sir or Ma'am. One reason is you may not know who is a Sir (male) or Madam (female) just from their profile names. Other reason is that respect can be shown without such salutations as well. $\endgroup$ – WYSIWYG Aug 28 '15 at 15:08
  • $\begingroup$ What did I say about cell differentiation? Same reason. Specialization of cells for a specific purpose so they express different genes than skin cells. They are the begin or the alimentary canal. This differentiation occurs very early on in development. $\endgroup$ – AMR Aug 29 '15 at 1:44

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