Coronary arteries are blood vessels that deliver oxygen-rich blood and nutrients to the heart, according to Johns Hopkins Medicine. Veins carry oxygen-poor blood back to the heart. The aorta is the main artery leaving the heart.
The aorta branches off into two main coronary arteries called the left main coronary artery and the right main coronary artery, explains the Cleveland Clinic. They are important because they supply blood that is critical to the heart muscle's function. Without a regular blood supply, a person can suffer a heart attack, which can lead to death. The arteries divide further into smaller vessels that supply all parts of the heart tissue.
The vessels are located on the outside of the heart, according to Johns Hopkins Medicine. They look like a web crisscrossing the heart muscle. At rest, a healthy adult heart beats between 50 and 90 times a minute, according to the Cleveland Clinic. An adult heart pumps about five quarts of blood each minute. In a healthy individual, blood takes about 20 seconds to circulate through the entire vascular system.
Atherosclerosis is a build-up of plaque, or cholesterol, which narrows the inside of the blood vessels or fully blocks the flow of blood through them, notes WebMD. This is a major cause of heart disease and strokes.