amnion

1 9.5

A thin inner bag that surrounds a young animal before it is born or hatched and holds protective fluid

noun
/ˈæmniən/

Specialized

: amnion

Furthermore, the zygote-formed embryos are enveloped by the yolk sac (this part does not develop in the human fetus), amnion, allantois, and chorion.

Examples

Once the symbiosis of gestation is at an end, our human entourage forms a second amnion.

Academic text (1997)
The amnion surface epithelial cells do not express HLA A, B, C, or DR or beta2-microglobulin.

Academic text (2007)
And it is face—textual and interpersonal—that drags me out of the amnion and clandestinity of "me" and pushes me into public view.

Academic text (1998)
The amnion is crucial for protecting the developing embryo during pregnancy.
In many reptiles, the amnion forms a protective layer around the egg.
Doctors can sometimes see the amnion during an ultrasound scan of the fetus.

Synonyms

amniotic sac

vsamnion

Specialized

1 4.4

A thin bag that surrounds and protects a developing baby in the womb

refers specifically to the innermost sac enclosing the developing embryo

embryonic membrane

vsamnion

Specialized

1 8.1

A thin skin that sometimes covers a baby's head when it is born

is the specific innermost sac rather than a general membrane term

amnios

vsamnion

Specialized

9.9

A thin inner sac of fluid that surrounds a developing baby in the womb

is the same term in another form for the same membranous sac

Surface Forms

amnion singular

amnia plural

Etymology

Amnion comes from the old Greek word amnos, which means 'lamb'. Early doctors thought the thin sac around a developing animal looked like a lamb's covering, so amnion now means the thin sac that protects the embryo.