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Noun: amniotic sac  ,am-nee'ó-tik sak
  1. Thin innermost membranous sac enclosing the developing embryo of higher vertebrates (reptiles, birds and mammals)
    - amnion, amnios

Derived forms: amniotic sacs

Type of: sac

Part of: amniote, fetal membrane

Encyclopedia: Amniotic sac