Which heart layer lines the inner surface of the heart chambers and valves?

Which heart layer lines the inner surface of the heart chambers and valves?

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

Answer: (B)

The inner lining of the heart chambers and valves is the endocardium. This is a thin, smooth layer of endothelial tissue that coats the inside surfaces of all four chambers and the heart valves, providing a low-friction surface for blood to flow and helping protect the heart muscle from direct contact with flowing blood. It’s continuous with the endothelium that lines all blood vessels, which helps keep the internal environment uniform as blood moves through the heart and vessels. By contrast, the muscular middle layer (myocardium) does the pumping, the outer surface (epicardium) forms the heart’s exterior and is part of the serous pericardium, and the surrounding fibrous sac (pericardium) encases the heart.

The inner lining of the heart chambers and valves is the endocardium. This is a thin, smooth layer of endothelial tissue that coats the inside surfaces of all four chambers and the heart valves, providing a low-friction surface for blood to flow and helping protect the heart muscle from direct contact with flowing blood. It’s continuous with the endothelium that lines all blood vessels, which helps keep the internal environment uniform as blood moves through the heart and vessels. By contrast, the muscular middle layer (myocardium) does the pumping, the outer surface (epicardium) forms the heart’s exterior and is part of the serous pericardium, and the surrounding fibrous sac (pericardium) encases the heart.