That's called "mucosa" in medicine. It's more absorptive than skin and often prone to micro-trauma. http://en.m.wikipedia.org/wiki/Mucous_membrane http://en.m.w

That's called "mucosa" in medicine. It's more absorptive than skin and often prone to micro-trauma. http://en.m.wikipedia.org/wiki/Mucous_membrane http://en.m.wikipedia.org/wiki/Mucous_membrane