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

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

Answer: (D)

Preventing backflow from the left ventricle into the left atrium is the job of the mitral valve, the left-sided atrioventricular valve. It sits between the left atrium and left ventricle and normally opens to allow blood to move from the atrium to the ventricle during filling. When the ventricle contracts, the pressure rises and the mitral valve snaps closed, blocking any reverse flow back into the atrium. This one-way mechanism helps maintain efficient forward flow toward the aorta. The pulmonary and aortic valves are semilunar valves that prevent blood from flowing back into the ventricles from the arteries, and the tricuspid valve is the right-sided atrioventricular valve between the right atrium and right ventricle.