The coronary arteries supply blood to the heart muscle itself. Damage to or blockage of a coronary artery can result in injury to the heart. Normally, blood flows through a coronary artery unimpeded. However, a process called atherosclerosis can cause a buildup of cholesterol and cells and other substances in the wall of the artery forming a plaque. If this process restricts blood flow enough it may result in a lack of oxygen to the heart muscle and cause angina. If the inner wall of a coronary artery becomes damaged, the inner contents of plaque can be exposed to the bloodstream and the body can bring substances such as platelets to the injured site and cause a further narrowing or complete blockage.
If blood flow is reduced severely or completely, death of part of the heart muscle that the artery supplies can occur. This is called a heart attack.