am·ni·on
noun/ˈæmniən/
/ˈæmniɑːn/
(plural amnions or amnia
(biology)/ˈæmniə/
/ˈæmniə/
)- the membrane (= thin layer) that surrounds the embryo of a human or an animal
包围人类或动物胚胎的膜（=薄层） Word Originmid 17th cent.: from Greek ‘caul’, diminutive of amnos ‘lamb’.