Which valve prevents backflow from the left ventricle to the left atrium?

• A. Aortic valve
• B. Mitral valve
• C. Tricuspid valve
• D. Pulmonary valve

Answer: (B)

Valves ensure one-way blood flow between heart chambers. The left atrioventricular valve, called the mitral valve, sits between the left atrium and left ventricle and closes as the left ventricle contracts. This prevents blood from flowing backward into the left atrium during systole. The other valves have different roles and locations: the aortic valve lies between the left ventricle and the aorta, the pulmonary valve sits between the right ventricle and the pulmonary artery, and the tricuspid valve is between the right atrium and right ventricle. So the valve that stops backflow from the left ventricle to the left atrium is the mitral valve.