|  amnion 
 
 thin innermost membranous sac enclosing the developing embryo of higher vertebrates (reptiles, birds and mammals)
 • Syn:
 amniotic sac, amnios
 • Derivationally related forms:
 amniotic, amnionic, amnic
 • Topics:
 mammal, mammalian
 • Hypernyms:
 sac
 • Part Holonyms:
 amniote, fetal membrane
 
 
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