What term describes the thin band of fibrous tissue that connects to the heart valves and prevents them from inverting?

The thin band of fibrous tissue that connects to the heart valves and prevents them from inverting is known as chordae tendineae. These structures are critical in the functioning of the heart's valves, particularly the atrioventricular valves (the mitral and tricuspid valves).

During ventricular contraction, the heart valves need to close tightly to prevent backflow of blood. The chordae tendineae are attached to the edges of the valves and run to papillary muscles, which are located on the ventricles' walls. When the ventricles contract, the papillary muscles also contract, which pulls on the chordae tendineae and keeps the valves closed. Without the chordae tendineae, the valves would likely invert or prolapse under the pressure created during ventricular contraction, leading to ineffective blood flow and potential heart failure.

The other terms listed refer to different components of heart anatomy. Papillary muscles play a supportive role, but it's the chordae tendineae that actively prevent valve inversion. The ventricular septum refers to the wall separating the left and right ventricles and does not have a role in valve function. Myocardium is the heart muscle itself, responsible for contraction but not directly involved in the valve mechanism.