What is the innermost layer of the heart wall?

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

Answer: (C)

Endocardium is the innermost layer of the heart wall. It lines the interior of the chambers and covers the heart valves, providing a smooth, low-friction surface for blood flow and forming a boundary between the blood and the heart muscle. Outside this thin layer lies the myocardium, the thick muscular layer responsible for pumping, and beyond that is the epicardium, the outer layer of the heart wall that is part of the serous pericardium. The pericardium surrounds the heart as a protective sac, but isn’t a layer of the heart wall itself.