There are 4 extraembryonic (made up of embryonic tissue but not actually part of the embryo proper) membranes that are found in all amniotic organisms:
Membrane........................Function in Egg Layers.................Function in Placentals
AMNION.......................Forms a sac around the ....................same
........................................embryo and fills w/ fluid
CHORION........................gas exchange mechanism..................placenta
..........................................just beneath shell
ALLANTOIS.....................forms a waste sac.............................umbilicus
YOLK SAC......................surrounds the yolk.............................vestigial
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