Amnion

from WordNet (r) 3.0 (2006)

amnion
    n 1: thin innermost membranous sac enclosing the developing
         embryo of higher vertebrates (reptiles, birds and mammals)
         [syn: {amnion}, {amniotic sac}, {amnios}]

from The Collaborative International Dictionary of English v.0.48

Amnion \Am"ni*on\, n. [Gr. ? the membrane round the fetus, dim.
   of ? lamb.] (Anat.)
   A thin membrane surrounding the embryos of mammals, birds,
   and reptiles.
   [1913 Webster]

from Moby Thesaurus II by Grady Ward, 1.0

22 Moby Thesaurus words for "amnion":
      allantoic membrane, amniotic sac, arachnoid membrane,
      basement membrane, conjuctiva, eardrum, hymen, maidenhead,
      membrana serosa, membrana tympana, membrane, meninges, meninx,
      neurilemma, pellicle, pericardium, perineurium, pleura, serosa,
      tympanic membrane, tympanum, velum

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