#fetal_membrane__fetalmembrane  any membrane that functions for the protection or nourishment of respiration or excretion of a developing fetus
  supertype:  tissue_layer__membrane  a pliable sheet of tissue that covers or lines or connects organs or cells of animals
  subtype:  allantois  caul  umbilical_cord
  part:  amnion__amniotic_sac__amnios  thin innermost membranous sac enclosing the developing embryo in higher vertebrates (Amniota: reptiles; birds; mammals)
  part:  chorion  outermost membranous sac enclosing the embryo in higher vertebrates (reptiles; birds; mammals)
     part:  chorionic_villus  one of the tiny villi that stick out of the fetal chorion and combine with the mother's uterine tissue to form the placenta

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