Describe the functions of the placenta and amniotic fluid, and explain the importance of the placental barrier.

3.3.1

a) Foetus: C

b) Umbilical cord: B

3.3.2 One function of amniotic fluid (A):

• It protects the fetus from mechanical shock or injury.
• It maintains a constant temperature for the fetus.
• It allows for fetal movement and development.
• It prevents adhesion of fetal parts to the amnion.

3.3.3 Region D (placenta) serves as a barrier between the growing foetus and the mother. Two reasons why this barrier is necessary:

• It prevents the mixing of maternal and fetal blood, which may have different blood groups or pressures, avoiding immunological reactions.
• It protects the fetus from certain harmful substances (e.g., toxins, some pathogens, drugs) that may be present in the mother's blood.
• It prevents the mother's immune system from attacking the fetus as a foreign body.

3.3.4

Feature	Blood moving from the mother to region D (maternal arterial blood)	Blood going from region D to the mother (maternal venous blood)
Oxygen content	High	Low
Nutrient content	High	Low
Waste content	Low	High