Which is the smaller chamber of the heart with thinner walls?

• A. Atria
• B. Ventricles
• C. Aorta
• D. Pulmonary Artery

Answer: (A)

Chambers differ in wall thickness because of their roles: receiving blood at low pressure vs pumping at high pressure. The smaller chamber with thinner walls is the atrium. Atria act as receiving rooms, collecting blood from the body and lungs and transferring it to the ventricles. Since they only need to move blood a short distance at low pressure, their walls are thin. In contrast, the ventricles are the thick-walled pumping chambers that must generate high pressure to send blood to the lungs and around the body. The aorta and pulmonary artery are vessels, not chambers, so they aren’t the correct choice.