Heart Chambers, Valves, and Blood Flow

The human heart has three tissue layers and is surrounded by the pericardium, a membrane that protects and confines it. The outermost layer, closest to the pericardium, is the epicardium. A pericardial cavity separates the pericardium from the epicardium.

Beneath the epicardium is the myocardium,...

The human heart, a muscle about the size of a fist is made up of three layers of tissue. The outermost layer, the epicardium, is surrounded by the pericardium, a membrane that protects the heart and keeps it in place. In the middle is the myocardium, cardiac muscle cells that make up the majority of the heart's walls which are lined on the insid...