Why is the left ventricle's muscle wall the thickest?

• A. Because it pumps blood to the lungs
• B. Because it pumps blood throughout the entire body
• C. Because it has no valves
• D. Because it receives blood from the atria only

Answer: (B)

The left ventricle has the thickest wall because it must generate a high amount of pressure to push blood through the entire body (systemic circulation). Pumping to all tissues requires overcoming a much greater resistance than sending blood to the lungs, so the left ventricle develops a thick, muscular wall to produce the strong systolic force needed. In contrast, the right ventricle only sends blood to the lungs, where the resistance is lower, so its wall is thinner. Valves exist to prevent backflow, so the idea that there are no valves isn’t correct, and the left ventricle doesn’t get blood directly from the atria—the atria transfer blood to the ventricles, but that isn’t the reason for the wall’s thickness.