Which heart layer is the muscular middle layer of the heart wall?

Which heart layer is the muscular middle layer of the heart wall?

• A. The muscular layer of the heart wall
• B. A thin layer that lines the surface of the heart
• C. The fibrous sac that encloses the heart
• D. A thin layer that lines the inside of the heart

Answer: (A)

The heart wall has three layers: the inner lining (endocardium), the muscular middle layer (myocardium), and the outer lining that covers the heart surface (epicardium, part of the serous pericardium). The muscular middle layer is the myocardium, which is made of cardiac muscle and is responsible for the heart’s contractions to pump blood. That makes it the correct choice. The other options correspond to the endocardium (inner lining), the epicardium (outer surface layer), and the fibrous pericardium (the tough fibrous sac surrounding the heart).

The heart wall has three layers: the inner lining (endocardium), the muscular middle layer (myocardium), and the outer lining that covers the heart surface (epicardium, part of the serous pericardium). The muscular middle layer is the myocardium, which is made of cardiac muscle and is responsible for the heart’s contractions to pump blood. That makes it the correct choice. The other options correspond to the endocardium (inner lining), the epicardium (outer surface layer), and the fibrous pericardium (the tough fibrous sac surrounding the heart).