Final answer:
The myocardium gets its blood supply from the coronary arteries, which are essential for delivering oxygenated blood to the heart's muscle cells. These arteries originate from the aorta, surround the heart, and their obstruction can lead to life-threatening conditions like myocardial infarction.
Step-by-step explanation:
Coronary Circulation and the Cardiac Cycle
The myocardium, the muscular tissue of the heart, requires a constant and dedicated blood supply, which it receives via the coronary arteries. These arteries originate from the first part of the aorta as it exits the left ventricle. The left and right coronary arteries arise from the left posterior and anterior aortic sinuses, respectively. The right coronary artery serves the right side of the heart and further divides into smaller branches, including the marginal arteries and the posterior interventricular artery, also known as the posterior descending artery. These vessel networks reach peak circulation when the heart muscle is relaxed (diastole) and reduce flow during heart contraction (systole).
Coronary arteries are crucial because they encircle the heart, much like a crown, and branch out into capillaries that provide oxygen and nutrients directly to the cardiomyocytes. After passing through capillaries, the deoxygenated blood is collected by coronary veins, which returns it to the right atrium for re-oxygenation through the lungs. The cardiac cycle involves systole and diastole phases, with the heart beating over 100,000 times per day.
A blockage in the coronary arteries, such as that caused by atherosclerosis, can lead to serious consequences including angina (chest pain) and even myocardial infarction (heart attack) due to the death of cardiac muscle tissue resulting from the lack of blood and oxygen.