Which of the following is NOT a component of the heart's conduction system?

The coronary sinus is responsible for draining deoxygenated blood from the heart muscles into the right atrium, but it does not play a role in the conduction system. The conduction system of the heart includes specialized structures that generate and propagate electrical impulses, which control the heart's rhythm and ensure efficient pumping of blood.

The sinoatrial node (SA) acts as the natural pacemaker of the heart, initiating electrical impulses that regulate heartbeats. The atrioventricular node (AV) receives these impulses from the SA node and provides a delay before transmitting the signal to the ventricles, allowing for coordinated contraction. The right and left bundle branches are pathways that carry the electrical signals through the ventricles, ensuring they contract simultaneously.

Thus, the only option among the choices that does not directly contribute to the heart's conduction system is the coronary sinus, distinguishing it from essential components that function in electrical conduction and heart rhythm regulation.