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[ep-uh-thee-lee-uh m] /ˌɛp əˈθi li əm/
noun, plural epitheliums, epithelia
[ep-uh-thee-lee-uh] /ˌɛp əˈθi li ə/ (Show IPA).
any animal tissue that covers a surface, or lines a cavity or the like, and that, in addition, performs any of various secretory, transporting, or regulatory functions.
Origin of epithelium
1740-50; < New Latin < Greek epi- epi- + thēl() teat + New Latin -ium -ium
Related forms
epithelial, adjective
interepithelial, adjective
nonepithelial, adjective
subepithelial, adjective
unepithelial, adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for epithelium
  • The epithelium varies considerably in different sections of the tubule.
  • It consists of a layer of connective tissue, the corium or mucosa, covered with epithelium.
  • The surface of the mucous membrane is covered by a single layer of columnar epithelium with occasional goblet cells.
  • It is lined by stratified squamous epithelium, which becomes transitional near the bladder.
  • The mucous lining of the lacrimal sac and nasolacrimal duct is covered with columnar epithelium, which in places is ciliated.
  • The epithelium varies according as the bladder is distended or contracted.
  • The vestibular membrane is thin and homogeneous, and is covered on its upper and under surfaces by a layer of epithelium.
  • The epithelium covering the mucous membrane is of the stratified squamous variety.
  • And areas surrounding the stroma produce growth factors that may stimulate the epithelium to turn cancerous, she adds.
  • Sneezing is a physiologic response to the irritation of the respiratory epithelium lining of the nose.
British Dictionary definitions for epithelium


noun (pl) -liums, -lia (-lɪə)
an animal tissue consisting of one or more layers of closely packed cells covering the external and internal surfaces of the body. The cells vary in structure according to their function, which may be protective, secretory, or absorptive
Derived Forms
epithelial, adjective
Word Origin
C18: New Latin, from epi- + Greek thēlē nipple
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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Word Origin and History for epithelium

1748, Modern Latin (Frederick Ruysch), from Greek epi "upon" (see epi-) + thele "teat, nipple" (see fecund). Related: Epithelial.

Online Etymology Dictionary, © 2010 Douglas Harper
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epithelium in Medicine

epithelium ep·i·the·li·um (ěp'ə-thē'lē-əm)
n. pl. ep·i·the·li·ums or ep·i·the·li·a (-lē-ə)
Membranous tissue composed of one or more layers of cells separated by very little intercellular substance and forming the covering of most internal and external surfaces of the body and its organs.

ep'i·the'li·al adj.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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epithelium in Science
Plural epithelia
The thin, membranous tissue that lines most of the internal and external surfaces of an animal's body. Epithelium is composed of one or more layers of densely packed cells. In vertebrates, it lines the outer layer of the skin (epidermis), the surface of most body cavities, and the lumen of fluid-filled organs, such as the gut or intestine.

epithelial adjective
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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