Non-pathological heart and great vessels, viewed from front and behind.
Note the significant number of vessels that cover the heart itself - though it moves blood around the entire body, it doesn’t just run on its own. The short loop of the coronary circulatory system is distinct from both the systemic circulation (where oxygenated blood travels to the rest of the body) and the pulmonary circulation (where deoxygenated blood travels from the right ventricle to the lungs, and back to the left ventricle of the heart).
When the coronary circulation is hindered or halted, the myocardium (heart muscle) is killed off. This can cause a myocardial infarction, or heart attack. Coronary bypass surgery takes blood vessels from other parts of the body and grafts them to parts of the coronary circulatory system that are clogged up or otherwise non-functional.
Diseases of the Heart and Aorta. Arthur Douglass Hirschfelder, 1912.