<Li> <P> Human embryo--length, 2 mm . Dorsal view, with the amnion laid open . X 30 . </P> </Li> <P> Human embryo--length, 2 mm . Dorsal view, with the amnion laid open . X 30 . </P> <Li> <P> Dorsum of human embryo, 2.11 mm in length . </P> </Li> <P> Dorsum of human embryo, 2.11 mm in length . </P>

When does the yolk sac become the placenta