Which heart layer is the thick muscular middle layer?

Which heart layer is the thick muscular middle layer?

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

Answer: (D)

The heart wall has three layers, and the thick muscular middle layer is the myocardium. This layer is made of cardiac muscle organized to produce the powerful contractions that pump blood. Its thickness varies by chamber, being greatest in the left ventricle to generate the high pressure needed for systemic circulation. The outer layer is the epicardium, part of the visceral pericardium, which helps protect and lubricate the heart. The inner layer is the endocardium, a thin lining of the chambers and valves made up mainly of endothelium. The pericardium surrounds the heart as a protective sac, not part of the heart wall itself.

The heart wall has three layers, and the thick muscular middle layer is the myocardium. This layer is made of cardiac muscle organized to produce the powerful contractions that pump blood. Its thickness varies by chamber, being greatest in the left ventricle to generate the high pressure needed for systemic circulation. The outer layer is the epicardium, part of the visceral pericardium, which helps protect and lubricate the heart. The inner layer is the endocardium, a thin lining of the chambers and valves made up mainly of endothelium. The pericardium surrounds the heart as a protective sac, not part of the heart wall itself.