What structures are known as the "heart strings" that prevent backflow to the atria?

The structures referred to as the "heart strings" are the chordae tendineae. These are thin, strong bands of connective tissue that attach the atrioventricular (AV) valves (the mitral and tricuspid valves) to the papillary muscles located on the ventricular walls. When the ventricles contract during systole, the pressure in the ventricles increases, causing the AV valves to attempt to close. The chordae tendineae play a crucial role in this process by preventing the valve cusps from prolapsing (flipping) back into the atria, which would allow for backflow of blood. By anchoring the valves securely and providing tension, the chordae tendineae ensure that the flow of blood is unidirectional, maintaining efficient circulation throughout the heart and body.

Other structures, such as the papillary muscles, do assist in this mechanism by contracting alongside the ventricles to help keep the chordae tendineae taut, but they are not referred to as "heart strings." The valve cusps themselves are the parts of the valves that close to prevent backflow. The interventricular septum is the wall dividing the left and right ventricles and plays no direct role in preventing backflow