What is the function of the mitral (bicuspid) valve?

• A. Allows blood to flow from the left atrium to the left ventricle
• B. Allows blood to flow from the left ventricle to the left atrium
• C. Permits blood to flow from the right atrium to the right ventricle
• D. Keeps the left ventricle empty at all times

Answer: (A)

The mitral valve sits between the left atrium and left ventricle and has two cusps, which is why it’s called bicuspid. Its job is to open to let blood flow from the left atrium into the left ventricle during ventricular filling (diastole), and then close to prevent blood from flowing backward into the atrium when the ventricle contracts (systole). This unidirectional flow ensures the ventricle fills properly and that blood is pumped forward into the aorta instead of regurgitating into the atrium. The other ideas describe flow in the wrong direction, involve the right heart’s valve, or suggest a condition that doesn’t reflect how valves regulate the heartbeat.