amniotic sac

1. The sac in which the foetus develops in mammals, reptiles, and birds.

   Near-synonym: amnion (meronymy, holonymy, or embryological sequence seem to vary by who is defining the two)

   Fruchtblase, Fruchtsack

   пло́дный пузы́рьplódnyj puzýrʹ

   thin innermost membranous sac enclosing the developing embryo of higher vertebrates (reptiles, birds and mammals)

regular