What is the epicardium?

• A. The epicardium is the thin outer layer of the cardiac wall, also known as the visceral layer of the serous pericardium.
• B. The thick muscular middle layer of the heart.
• C. The inner lining of the heart chambers.
• D. The fibrous outer layer surrounding the heart.

Answer: (A)

The epicardium is the outer surface of the heart itself. It is a thin, smooth layer that covers the heart and is the visceral layer of the serous pericardium. This layer helps reduce friction as the heart beats and houses part of the coronary vessels within a layer of fat called epicardial fat. It is continuous with the parietal serous pericardium at the great vessels.

It is not the thick muscular middle layer of the heart (that’s the myocardium), nor the inner lining lining the chambers (the endocardium), nor the fibrous outer layer surrounding the heart (the fibrous pericardium).