Which structure in the heart prevents backflow into the right atrium?

The tricuspid valve is the structure in the heart that prevents backflow into the right atrium. Located between the right atrium and right ventricle, this valve ensures that blood flows in one direction—from the atrium to the ventricle—during the heart's pumping cycle. When the right ventricle contracts to send blood into the pulmonary artery, the tricuspid valve closes, preventing any blood from flowing backward into the right atrium. This one-way flow is crucial for the efficient functioning of the heart and the overall circulatory system.

The other valves mentioned serve different purposes in the heart. The aortic valve prevents backflow from the aorta into the left ventricle, the pulmonary valve prevents backflow from the pulmonary artery into the right ventricle, and the mitral valve functions similarly to the tricuspid valve but is located between the left atrium and left ventricle. Each valve plays a specific role in maintaining proper blood circulation throughout the heart and body, but in the context of preventing backflow into the right atrium, the tricuspid valve is the key structure involved.