Which part does the right vagus nerve primarily innervate?

The right vagus nerve primarily innervates the sinoatrial (SA) node of the heart. The SA node, located in the right atrium, is known as the natural pacemaker of the heart because it generates electrical impulses that initiate the heartbeat. The right vagus nerve's parasympathetic innervation acts to modulate the heart rate, primarily by decreasing it.

While both the SA node and the atrioventricular (AV) node receive vagal innervation, it is predominantly the right vagus nerve that influences the SA node. The left vagus nerve more significantly affects the AV node. Therefore, the role of the right vagus nerve in directly innervating the SA node and facilitating the regulating of heart rate is fundamental in understanding its function within the cardiac autonomic system.

In summary, the correct answer identifies the primary target of the right vagus nerve, underscoring its role in the autonomic regulation of heart rhythm.