epicardium

The epicardium is the heart's own outer skin — the thin, glistening layer that wraps the muscle. Picture shrink-wrap clinging snugly to the surface of the heart: that is roughly what this layer looks like.

It is the outermost layer of the heart wall, lying directly on top of the myocardium. It is also known as the visceral pericardium, because it is the inner of the two layers of the pericardial sac that surrounds the heart. Between it and the outer pericardial layer is a small amount of lubricating fluid that lets the beating heart glide smoothly.

The epicardium is more than a wrapper: it contains the main coronary arteries and veins that run across the surface of the heart before diving into the muscle, along with a cushioning layer of fat. Inflammation of the pericardial layers (pericarditis) can cause sharp chest pain and a scratchy rubbing sound heard through a stethoscope.