DR G. MOSCOSO / SCIENCE PHOTO LIBRARY DR G. MOSCOSO / SCIENCE PHOTO LIBRARY
Embryo. Human embryo at six to seven weeks of age. It is floating in the protective amniotic fluid of its amniotic sac. The embryo is attached to the placenta (lower centre) by its umbilical cord (upper left). Nutrients and oxygen pass from the mother to the embryo through this cord, while waste products pass in the opposite direction. At this age, the embryo is between 13 to 22 millimetres in length, and its fingers and toes are separating. After eight weeks of development the embryo is known as a foetus.
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