amnion

[am-nee-uh n]

SEE MORE SYNONYMS FOR amnion ON THESAURUS.COM

noun, plural am·ni·ons, am·ni·a [am-nee-uh] /ˈæm ni ə/.

Anatomy, Zoology. the innermost of the embryonic or fetal membranes of reptiles, birds, and mammals; the sac in which the embryo is suspended.

Zoology. a similar membrane of insects and other invertebrates.

RELATED WORDS

afterbirth, placenta

Origin of amnion

1660–70; < Greek, equivalent to amn(ós) lamb (see yean) + -ion diminutive suffix

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for amnion

Historical Examples of amnion

Amnion: the inner of the two membranes enveloping the embryo.
Explanation of Terms Used in Entomology
John. B. Smith
The embryo when about to hatch throws off the egg-shell and amnion in a few seconds.
Our Common Insects
Alpheus Spring Packard
Only in the chancel were they protected by sheep's amnion stretched on frames.
Pabo, The Priest
Sabine Baring-Gould
The amnion contains a fluid known by the name of liquor amnii.
A System of Midwifery
Edward Rigby
Both it and the stalk of the yolk-sack are enveloped by the amnion (am).
The Works of Francis Maitland Balfour, Volume III (of 4)
Francis Maitland Balfour

British Dictionary definitions for amnion

amnion

noun plural -nions or -nia (-nɪə)

the innermost of two membranes enclosing an embryonic reptile, bird, or mammalSee also chorion

Word Origin for amnion

C17: via New Latin from Greek: a little lamb, from amnos a lamb

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for amnion

1660s, Modern Latin, from Greek amnion "membrane around a fetus," said to be originally "bowl in which the blood of victims was caught" [Liddell & Scott], which is variously said to be of unknown origin, from ame "bucket," or a diminutive of amnos "lamb."

Medicine definitions for amnion

amnion

[ăm′nē-ən, -ŏn′]

n. pl. am•ni•ons

The thin, membranous sac filled with a serous fluid in which the embryo or fetus is enclosed and suspended in the uterus.amniotic sac

Related formsam′ni•ot′ic (-ŏt′ĭk) null adj.

Science definitions for amnion

amnion

[ăm′nē-ən]

A thin, membranous sac filled with a watery fluid (called the amniotic fluid) in which the embryo or fetus of a reptile, bird, or mammal is suspended during prenatal development. Also called amniotic sac