amnion

[am-nee-uhn]

noun

plural

amnions, amnia 

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

2. Zoology.,  a similar membrane of insects and other invertebrates.

amnion

/ ˈæmnɪən /

noun

1. the innermost of two membranes enclosing an embryonic reptile, bird, or mammal See also chorion

amnion

1. 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.

2. Also called amniotic sac

Word History and Origins

Origin of amnion¹

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

Word History and Origins

Origin of amnion¹

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

Example Sentences

But a single placenta can make anywhere between 50 to 100 amnion grafts.

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A method to correctly specify amnion formation is important to be able to recapitulate human embryo development as closely as possible using stem cell-based embryo models.

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Its major adaptive advantage is the amnion — an enclosing membrane that prevents the embryo from drying out, and the principal feature to which the amniotic egg owes its name.

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Until recently, pre-natal screening required invasive procedures such as amniocentesis, in which the fluid from the sac surrounding the foetus, the amnion, is sampled and the DNA examined for genetic abnormalities.

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The embryo of a moth, a dragon-fly or a bug is invaginated into the yolk at the head end, the portion of the blastoderm necessarily pushed in with it forming the amnion.

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