Algonquin College Health Program Assessment (AC-HPAT) Practice Exam

What is the primary function of a valve in a vein?

1. To increase blood flow

2. To prevent reverse blood flow

3. To transport oxygen

4. To absorb nutrients

The correct answer is: To prevent reverse blood flow

The primary function of a valve in a vein is to prevent reverse blood flow. Veins transport deoxygenated blood back toward the heart against the force of gravity, especially in the limbs. The valves within the veins act as one-way gates that allow blood to flow in only one direction—toward the heart—and prevent backflow. This is particularly important in the lower extremities, where the challenge of gravity makes it more difficult for blood to return to the heart. The presence of valves ensures that blood does not pool in the veins, which could lead to venous insufficiency or varicose veins. The coordinated contraction of surrounding muscles, known as the "muscle pump," along with the action of the valves, facilitates efficient circulation throughout the body. Other options, such as increasing blood flow, transporting oxygen, or absorbing nutrients, do not accurately reflect the specific role of valves in the venous system. Instead, these functions are carried out by other components of the cardiovascular system, such as arteries and capillaries.