Epithelial tissues are found on all the surfaces of the body; including external surfaces and surfaces of organs etc. Are there any surfaces which do not have epithelial? I have read in my book that almost all the surfaces has epithelial tissues but there are some exceptions. What are the exceptions?

Similarly, almost all the epithelial tissues are avascular. But there are some exceptions which are vascular? Which epithelial tissues are vascuar?

*I'm talking about a human body.

  • $\begingroup$ Epithelial tissue is vascular, dead epithelial cells form the surface of skin, hair and nails. $\endgroup$ – user22339 Nov 4 '13 at 13:42
  • $\begingroup$ no, epithelial tissues are avascular @Skippy-psI'mawoman. A few exceptions are vascular. I want to know what are these exceptions. $\endgroup$ – Rafique Nov 4 '13 at 13:57
  • $\begingroup$ Well we have different understanding then.. perhaps you'd like to cite your source> $\endgroup$ – user22339 Nov 4 '13 at 14:48
  • $\begingroup$ read the 4th line. en.wikipedia.org/wiki/Epithelium $\endgroup$ – Rafique Nov 4 '13 at 15:03
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    $\begingroup$ vascular wall cells are called endothelial cells. $\endgroup$ – WYSIWYG Nov 4 '13 at 16:14

I think you're talking about two different things. I assume Rafique is referring to vascularized epithelium, but user4693 is referring to vascular epithelium. Although the terminology is very similar, the difference is important.

vascular epithelium = endothelium of a blood or lymphatic vessel.

vascularized epithelium = epithelium with a blood supply, meaning that small vessels invade the epithelium (pass between epithelial cells) rather than simply occurring in the underlying basement membrane or connective tissue.

Most epithelia are avascular (lack blood vessels). As far as I know the only vascularized epithelium in humans is found in the inner ear (1). I've been told that the lips have vascularized epithelium (which is why they appear reddish), but I don't completely trust that source and I cannot find anything online to support it.

Also, some pathological conditions can cause vascularization of certain epithelia, like the cornea (2).

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  • $\begingroup$ I suppose "vascular eipthelium" could be a correct term, but I've always seen endothelium (or endothelial as adj as @wysiwyg pointed out). Perhaps this helps prevent the confusion. $\endgroup$ – Atl LED Jan 9 '14 at 20:00
  • $\begingroup$ I've always used endothelium. However, I noticed that some online sources (notably wikipedia) use the term "vascular epithelium". I thought that may be why earlier comments disagreed, so I was trying to, hopefully, provide some clarification. $\endgroup$ – user5373 Jan 9 '14 at 21:09

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