Which is the larger chamber of the heart with thicker muscular walls?

• A. Ventricles
• B. Atria
• C. Valves
• D. Septum

Answer: (A)

The key idea is that wall thickness in the heart matches the pressure the chamber needs to generate. The ventricles are the large, thick-walled chambers because they have to pump blood out of the heart—the right ventricle sends blood to the lungs at relatively low pressure, while the left ventricle must create high pressure to push blood through the entire body. That thick muscular wall, especially in the left ventricle, makes ventricles the stronger, more muscular chambers overall. In contrast, the atria have thinner walls since they only collect blood at low pressure before it moves into the ventricles. Valves and the septum aren’t chambers at all—valves regulate flow and the septum divides the chambers.