During large heart attacks the chordae tendineae can be damaged. Use your knowledge of the heart’s structure and the diagram below to to explain how damage to these structures may lead to backflow of blood from the right ventricle to the right atrium.

The heart is a muscular pump. It can be divided into 4 chambers: 2 atria and 2 ventricles. Each atrium is connected to its ventricle by a small opening. This opening is covered by a valve, which guards the entrance and exit of blood. These valves only allow the passage of blood from the atria to the ventricles. No backflow of blood from the ventricles to the atria is normally possible. Between the right atrium and right ventricle lies the tricuspid valve. This valve has 3 cusps which are supported by the tendinous cords. During ventricular systole (contraction), blood will be forced at high pressures against the tricuspid valve. To stop the valves from simply flopping back into the atria, the tendinous cords hold each of the 3 valve cusps firmly in place. Damage to these tight cords will mean that the leaflets of the tricuspid valve will no longer be supported. The high pressure generated by the ventricle will overwhelm the unsupported valve and lead to backflow of blood from the right ventricle to the right atria.