AQA A Level PE – The Cardiovascular System Practice Test

Pocket valves are valves located in veins that prevent backflow. Which statement best describes their function?

They regulate arterial flow They transport nutrients They prevent backflow of blood in the veins They assist with blood clotting

Correct Answer:

They prevent backflow of blood in the veins

Explanation:

Valves in veins are all about keeping blood moving in the right direction to aid return to the heart. Pocket valves are one-way flaps formed by folds of the inner lining. They open to let blood flow toward the heart and snap shut if blood tries to move backward, preventing backflow. This is especially important in the legs, where blood must work against gravity, aided by muscle contractions that squeeze the veins to push blood upward. So the function described is that these valves prevent backflow of blood in the veins. They don’t regulate arterial flow, transport nutrients, or directly affect clotting.

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