Which structure completely surrounds the heart, composed of the parietal and visceral pericardium?

• A. Fibrous Pericardium
• B. Visceral Pericardium
• C. Parietal Pericardium
• D. Pericardial Fluid

Answer: (A)

The surrounding structure is the outer tough sac that encases the heart. The fibrous pericardium forms the thick, durable outer wall of this sac, anchoring the heart in the middle of the chest and preventing overexpansion. Inside that fibrous layer sits the serous pericardium, which is made of two layers: the parietal layer lining the inner surface of the fibrous pericardium and the visceral layer covering the heart. These two layers meet to create the pericardial cavity, which contains a small amount of lubricating fluid. While the parietal and visceral pericardium are parts of the serous layer, they do not alone form the complete enclosure—the fibrous pericardium does. Pericardial fluid is the lubricant, not the enclosing structure.