Final answer:
Typically, the SA and AV nodes are supplied by the right coronary artery in a left dominant circulation, but anatomical variations can lead to differences in their blood supply. The left anterior descending artery also plays a critical role in supplying the heart muscle and may contribute to nodal blood supply through anastomoses.
Step-by-step explanation:
In individuals with a left dominant circulation, the sinoatrial (SA) and atrioventricular (AV) nodes are primarily supplied by the right coronary artery (RCA). Under normal circumstances, the SA node is fed by the SA nodal artery, which typically branches from the RCA, although in some individuals it may arise from the left coronary circulation. The AV node is usually supplied by the AV nodal artery, which emerges from the RCA as well. However, the exact vascular supply to these nodes can vary between individuals.
The left coronary artery gives rise to two main branches: the anterior interventricular artery (left anterior descending or LAD) and the circumflex artery. The anterior interventricular artery closely follows the anterior interventricular sulcus, and through its branches, it supplies the interventricular septum and parts of the right and left ventricles. While the circumflex artery extends along the coronary sulcus before anastomosing with the branches of the RCA. It's important to recognize that in some cases, anastomotic connections between LAD and branches of the posterior interventricular artery may contribute to the blood supply of the SA and AV nodes especially when they arise from the left coronary circulation in left dominant hearts.