The coronary arteries are the first vessels to branch from the aorta, and they provide a crucial supply of oxygen and nutrients to the layers of the heart. The right coronary artery and its branches mostly supply the right side of the heart, although they
The coronary arteries are the first vessels to branch from the aorta, and they provide a crucial supply of oxygen and nutrients to the layers of the heart. The right coronary artery and its branches mostly supply the right side of the heart, although they also reach part of the left atrium, a posterior portion of the left ventricle, and even the posterior third of the interventricular septum. Unlike vessels in peripheral locations of the body, these vessels dilate during exertion to meet the increased demands of the myocardium. However, the lack of anastomoses amongst the coronary arteries leaves the heart at risk of ischemia and infarction if blood flow through the vessels is severely compromised, such as with atherosclerosis.
The right coronary artery finds its origin from the aorta immediately above the right (coronary) semilunar cusp of the aortic valve. It follows a course between the pulmonary trunk and right atrium in the right atrioventricular groove and curves around the acute angle of the heart. The major branches of the right coronary artery include the sinoatrial (SA) nodal branch, the right (acute) marginal branch, the posterior interventricular branch (commonly referred to as the posterior descending artery, PDA), and the posterolateral branch.
The posterior interventricular and posterolateral arteries branch from the right coronary artery in about 70% of the population. Individuals with this configuration are considered to have a “right dominant” coronary circulation. If these arteries arise from the circumflex branch of the left coronary artery, the heart has a “left dominant” orientation. When both the right and left coronary arteries contribute to these branches, the heart has a “balanced” circulation.
The coronary arteries are composed of three layers: tunica intima, tunica media, and tunica adventitia.
The tunica intima is the lining inside the vessels comprised of the endothelium, sub-endothelium, and internal elastic lamina. Simple squamous cells make up the inner-most layer, which functions not only as a barrier allowing blood to flow smoothly but also for pinocytosis, diapedesis, and secretions into the lumen or back into the smooth muscle to produce nitrous oxide (NO). A break in any part of the endothelial lining exposes blood to the subendothelial layer which starts the clotting mechanism. Discontinuity of the simple squamous endothelium can initiate the process of