3.11 describe the role of the placenta in the nutrition of the developing embryo

- placenta forms as an embryo develops
- developing fetus is connected to the placenta
- allows diffusion of glucose, amino acids and oxygen from the mother's blood to fetus and waste carbon dioxide and urea taken away.

Placenta: connection of the fetus and the mother between uterine wall via the umbilical cord that allows the exchange of materials between the mother and the fetus.
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Explanation:

• Placenta is lined with villi to increase surface area for diffusion of materials between mother and fetus.
• Fetal capillaries and maternal capillaries are very close therefore there is a short diffusion distance, and diffusion will be efficient.

Materials including oxygen, water, vitamins, minerals and antibodies are carried from mother to fetus. Waste materials are carried from fetus to mother. This means that drugs such as nicotine and alcohol can also cross placenta and potentially damage the fetus.

Key Idea: There is NO mixing of maternal and fetal blood in the placenta.

This is because:

1. maternal blood has much higher pressure than fetal blood. If fetus were to be connected to maternal circulatory system, its blood vessels would burst.

2. fetus and mother have different blood groups and can trigger clotting.

Therefore what happens in placenta is:

- mother's blood empties into spaces in placenta and babies' blood is carried by umbilical artery into capillaries in villi.