The Relationship Between Blood Flow and Perfusion in the Lungs

Blood flow is greatest at the _____ of the lungs and perfusion is greatest at the _____ of the lungs.

A. apex; apex
B. apex; base
C. base; base
D. base; apex

Final answer:

Blood flow and perfusion are both greatest at the base of the lungs due to the effects of gravity on blood, making the correct answer C. base; base.

Explanation:

The original question addresses the differences in blood flow and perfusion in different parts of the lungs. In a standing person, blood flow is typically greatest at the base of the lungs due to gravity. On the other hand, perfusion, which is the flow of blood in the pulmonary capillaries where gas exchange occurs, is also greatest at the base of the lungs. This is because when standing, blood is pulled to the lower parts of the lungs by gravity, enhancing perfusion there. Therefore, the correct answer is C. base; base.

For educational supplementation, let's do a brief review: The pulmonary artery carries deoxygenated blood to the lungs, and the pulmonary vein carries oxygenated blood back to the heart. Blood flows from the heart through arteries to capillaries, where gas exchange occurs; then, it travels through venules into veins, which return the blood to the heart. Finally, gas exchange in the lungs takes place in alveoli, where blood becomes oxygenated. Gas moves in the direction of high pressure to low pressure to facilitate this process.