The two upper chambers of the heart are called the

The two upper chambers of the heart are called the

• A. atria
• B. ventricles
• C. valves
• D. septum

Answer: (A)

The two upper chambers are the atria. They act as receiving rooms for blood returning to the heart. The right atrium collects deoxygenated blood from the body via the superior and inferior vena cavae (and the coronary sinus), while the left atrium collects oxygenated blood from the lungs via the pulmonary veins. When the atria contract, they push blood into the ventricles through the atrioventricular valves—the tricuspid valve on the right and the mitral valve on the left. The atria have thinner walls because they only need to move blood a short distance to fill the ventricles.