What is a function of the placenta?
A) acts as a barrier to prevent some toxins reaching the fetus
B) exchanges blood between the mother and the fetus
C) prevents the transfer of excretory products from the fetus
D) protects the fetus from mechanical damage
▶️ Answer/Explanation
Ans: A
The placenta has multiple functions, including acting as a selective barrier (A) that blocks some harmful substances (like certain toxins and pathogens) while allowing nutrients and oxygen to pass through.
While it facilitates nutrient/waste exchange, it does not directly exchange blood (B) – maternal and fetal blood remain separate. Excretory products (C) are transferred to the mother for elimination, and mechanical protection (D) is primarily provided by the amniotic sac and fluid.
Thus, the most accurate answer is A.
The diagram shows part of a placenta and umbilical cord.
What is the function of the umbilical vein?
A) to stop pathogens passing into the fetus
B) to stop toxins passing into the fetus
C) to transport carbon dioxide away from the fetus
D) to transport oxygen to the fetus
▶️ Answer/Explanation
Ans: D
The umbilical vein carries oxygenated blood and nutrients from the placenta to the fetus. This is crucial for fetal development, as oxygen is required for cellular respiration.
Options A and B describe functions of the placental barrier, not the umbilical vein. Option C is incorrect because carbon dioxide is transported away from the fetus via the umbilical arteries, not the vein. Thus, the correct answer is D.