Which of the following correctly lists the three major layers of the heart wall?

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

Answer: (A)

The heart wall is organized from inside to outside as endocardium, myocardium, and epicardium. The endocardium lines the heart chambers and valves and is continuous with the endothelium of the blood vessels, forming a smooth surface for blood flow. The thick middle layer, the myocardium, is made of cardiac muscle responsible for the heart’s contractions and pumping action. The outer layer, the epicardium, is the visceral layer of the serous pericardium and covers the myocardium; it transitions into the pericardial sac that surrounds the heart. The pericardium as a whole is not a layer of the heart wall, so lists that include pericardium as a wall layer aren’t correct.