Which term refers to the inner layer of the heart?

• A. Endocarditis
• B. Endoderm
• C. Endomysium
• D. Endocardium

Answer: (D)

The inner lining of the heart is the endocardium. It lines the heart chambers and covers the heart valves, providing a smooth surface for blood to flow over. This layer sits just beneath the myocardium (the muscular heart wall) and is continuous with the lining of the blood vessels.

Endocarditis would be inflammation of that lining, not the name of the layer itself. Endoderm is a germ layer from early embryonic development that forms parts of the gut and associated organs, not a heart lining. Endomysium is the connective tissue surrounding individual muscle fibers, not the lining of the heart chambers. So the term that correctly identifies the inner layer is endocardium.