Which of the following correctly defines coronary artery disease?

Coronary artery disease (CAD) refers specifically to the condition in which the coronary arteries, responsible for supplying blood to the heart, become narrowed or blocked due to plaque buildup, which typically consists of fat, cholesterol, and other substances. This blockage restricts blood flow to the heart muscle, which can lead to symptoms such as angina (chest pain) or more severe complications like a heart attack.

Understanding CAD is crucial because the heart muscle requires a continuous supply of oxygen-rich blood to function effectively. When there is a reduction in blood flow due to blockage, it can severely impact the heart's ability to pump blood throughout the body, leading to serious health issues.

The other options relate to different conditions. For instance, blockage of blood flow to the lungs relates to pulmonary vascular problems, blockage to the brain pertains to cerebrovascular accidents like strokes, and blockage to the extremities often refers to peripheral artery disease (PAD). Each of these conditions affects different systems in the body but does not specifically define coronary artery disease.