Which of the following is NOT part of the conduction pathway in the heart?

The conduction pathway in the heart is responsible for the coordinated electrical impulses that stimulate heart contractions. This pathway includes structures such as the sinoatrial (SA) node, atrioventricular (AV) node, bundle of His, and the right and left bundle branches, along with the Purkinje fibers. Each of these components plays a crucial role in ensuring that the heart beats in an organized and effective manner.

The coronary sinus is a large vein that collects deoxygenated blood from the heart muscle and drains into the right atrium. It serves as a conduit for blood returning from the coronary circulation but does not participate in the conduction system that initiates and regulates the heartbeat. Therefore, it is not considered part of the conduction pathway.

In contrast, the Purkinje fibers, left bundle branch, and right bundle branch are integral components of the heart’s conduction system. The Purkinje fibers transmit the electrical impulses to the myocardial cells, facilitating coordinated contraction of the ventricles. The left and right bundle branches conduct impulses from the bundle of His through the ventricular walls, ensuring that the heart's chambers contract in a synchronized manner.

Understanding the distinctions within cardiac physiology, particularly the roles of different structures, is vital for anyone studying cardiovascular perfusion and