from
The Collaborative International Dictionary of English v.0.48
Epithelium \Ep`i*the"li*um\, n.; pl. E. {Epitheliums}, L.
{Epithelia}. [NL., fr. Gr. 'epi` upon + ? nipple.] (Anat.)
The superficial layer of cells lining the alimentary canal
and all its appendages, all glands and their ducts, blood
vessels and lymphatics, serous cavities, etc. It often
includes the epidermis (i. e., keratin-producing epithelial
cells), and it is sometimes restricted to the alimentary
canal, the glands and their appendages, -- the term
endothelium being applied to the lining membrane of the blood
vessels, lymphatics, and serous cavities.
[1913 Webster]