noun Embryology.
the outer germ layer in the embryo of a metazoan.
Also called ectoblast.

1860–65; ecto- + -derm

ectodermal, ectodermic, adjective
ectodermoidal [ek-toh-der-moid-l] , adjective
subectodermal, adjective
subectodermic, adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
ectoderm or exoderm (ˈɛktəʊˌdɜːm)
mesoderm See also endoderm the outer germ layer of an animal embryo, which gives rise to epidermis and nervous tissue
exoderm or exoderm
ecto'dermal or exoderm
ecto'dermic or exoderm

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Word Origin & History

1861, from ecto- + derm.
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Medical Dictionary

ectoderm ec·to·derm (ěk'tə-dûrm')
The outermost of the three primary germ layers of an embryo, from which the epidermis, nervous tissue, and sense organs develop. Also called ectoblast.

ec'to·der'mal or ec'to·der'mic 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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American Heritage
Science Dictionary
ectoderm  [%PREMIUM_LINK%]     (ěk'tə-dûrm')  Pronunciation Key 
The outermost of the primary germ layers of an animal embryo. In vertebrates, the ectoderm gives rise to the epidermis and associated tissues (such as hair and sweat glands), enamel of the teeth, sense organs, nervous system, and lining of the nose, mouth, and anus. Compare endoderm, mesoderm.

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


the outermost of the three germ layers, or masses of cells, which appears early in the development of an animal embryo. In vertebrates, ectoderm subsequently gives rise to hair, skin, nails or hooves, and the lens of the eye; the epithelia (surface, or lining, tissues) of sense organs, the nasal cavity, the sinuses, the mouth (including tooth enamel), and the anal canal; and nervous tissue, including the pituitary body and chromaffin tissue (clumps of endocrine cells). In adult cnidarians and ctenophores, the body-covering tissue, or epidermis, is occasionally called ectoderm. See also endoderm; mesoderm.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
In fact, epithelial tissue can be derived from either the ectoderm or endoderm.
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