What structures of the heart keep blood flowing in one direction.?

There are four main structures in the heart that help keep blood flowing in one direction:

1. Atrioventricular (AV) Valves: The tricuspid valve on the right side and the mitral (or bicuspid) valve on the left side of the heart prevent backflow of blood from the ventricles into the atria when the ventricles contract.

2. Semilunar Valves: The pulmonary valve in the pulmonary artery and the aortic valve in the aorta prevent backflow of blood from the arteries back into the heart when the ventricles relax.

3. Chordae Tendineae: These thin, fibrous cords connect the cusps (leaflets) of the AV valves to papillary muscles in the ventricles. When the ventricles contract, the papillary muscles pull the chordae tendineae, preventing the AV valves from being pushed back into the atria.

4. Myocardial Contractions: The coordinated contractions of the heart muscle (myocardium) ensure a sequential flow of blood through the chambers. The regular and rhythmic contraction of the heart's chambers helps propel blood forward, preventing any backward flow.

Together, these structures work in harmony to maintain the unidirectional flow of blood within the heart, ensuring that oxygen-rich blood is pumped out to the body and deoxygenated blood is directed to the lungs for oxygenation.