The inner lining of the heart chambers is called the?

• A. Endocardium
• B. Epicardium
• C. Myocardium
• D. Pericardium

Answer: (A)

The inner lining of the heart chambers is the endocardium. The heart wall has three layers: the endocardium on the inside, the myocardium as the muscular middle layer, and the epicardium as the outer layer. The endocardium is a thin, smooth membrane made of endothelial cells that lines the chambers and covers the heart valves. This smooth surface reduces friction as blood flows through the chambers and valves, and it’s continuous with the lining of the great vessels as blood exits and enters the heart. In the subendocardial area, you’ll also find parts of the heart’s conduction system, which helps coordinate the heartbeat. By contrast, the epicardium forms the outer layer, the myocardium is the thick muscular layer that actually contracts to pump blood, and the pericardium is the surrounding sac that encloses the heart.