Epithelium

n. layer of cells lining bodily organs and surfaces (Biology)

In biology and medicine, epithelium is a tissue composed of a layer of cells. Epithelium lines both the outside (skin) and the inside cavities and lumen of bodies. The outermost layer of our skin is composed of dead stratified squamous, keratinized epithelial cells. Mucous membranes lining the inside of the mouth, the esophagus, and part of the rectum are lined by nonkeratinized stratified squamous epithelium. Other, open to outside body cavities are lined by simple squamous or columnar epithelial cells. Other epithelial cells line the insides of the lungs, the gastrointestinal tract, the reproductive and urinary tracts, and make up the exocrine and endocrine glands. The outer surface of the cornea is covered with fast-growing, easily-regenerated epithelial cells.
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Epithelium /ep·i·the·li·um/ pl. epithe´lia [Gr.] the cellular covering of internal and external body surfaces, including the lining of vessels and [more]Epithelium - Community and Resources

Noun
1. membranous tissue covering internal organs and other internal surfaces of the body
(synonym) epithelial tissue
(hypernym) animal tissue
(hyponym) endothelium
(part-meronym) epithelial cell

n. epithelium, layer of cells lining bodily organs and surfaces (Biology)