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Placenta. Gross clinical specimen of a human placenta and the umbilical cord (white). The placenta is a vascular organ that consists of a ramification of blood vessels and capillaries encased in a membrane. It is responsible for the respiration and excretion of the growing foetus. Blood flows to and from the foetus via the umbilical cord to the placenta. There, the network of capillaries are surrounded by pools of the mother's blood. Carbon dioxide and other wastes diffuse out of the foetal blood and into the mother's blood. Oxygen and other nutrients diffuse into the foetal blood. The foetal blood and mother's blood do not mix.
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