Question

What arteries supply blood to the myocardium?

Answer 1

Right and Left Coronary Arteries and their branches

Explanation:

Arterial Supply of the Heart
The Coronary Arteries supply both the myocardium and epicardium. They course deep to the epicardium and are normally embedded in fats. There are two coronary arteries found in the heart (the left and the right coronary arteries), which arise from the aortic sinuses at the proximal part of the ascending aorta (just superior to the aortic valve).

Right Coronary Artery
Arises from the right aortic sinus and runs in the coronary groove (coronary sulcus), and in the atrioventricular groove (atrioventricular sulcus). Its branches include the following:

1. Sinoatrial Nodal Branch -> supplies SA Node
2. Right Marginal Branch -> supplies right border of the heart towards the apex
3. Atrioventricular Nodal Branch -> supplies the AV Node
4. Posterior Interventricular Br./ Posterior Descending -> supplies the adjacent areas of both ventricles and sends perforating interventricular septal branches into the IV septum

The blood flow through the right coronary artery is as follows

1. Right coronary artery ---> SA Nodal Branch ---> Right Marginal Branch ---> Posteriorly
2. Right coronary artery ---> AV Nodal Branch ---> Descends as the Posterior Interventricular Branch ---> Terminal Branch

Left Coronary Artery
Arises from the left aortic sinus of the ascending aorta and passes between the left auricle and the left side of the pulmonary trunk and runs in the coronary sulcus. The branches of the left coronary artery are the ff:

1. SA Nodal Branch -> supplies SA Node (arises from the circumflex branch of the LCA and ascends on the posterior surface of the left atrium to the SA Node)
2. Anterior Interventricular Br./ Left Anterior Descending -> supplies adjacent parts of both ventricles and the anterior 2/3 of the interventricular septum (via IV septal branches)
3. Circumflex Branch -> may supply the SA Nodal Branch, may also supply a branch that runs in or adjacent to the posterior IV groove
4. Left Marginal Branch -> supplies the left ventricle

Fig 1: Sternocostal aspect of the heart with labels for the arterial supply and venous drainage

Fig 2: Diaphragmatic view of the heart with labels for the arterial supply and venous drainage

*Dominance of the coronary arterial system is defined by the artery which would give rise to the posterior interventricular branch

*Both images in this response are sourced from Netter - Atlas of Human Anatomy