Heart Wall

The heart wall has three distinct layers working together to pump blood tirelessly. The inner endocardium is smooth endothelium over connective tissue, preventing clots and providing a low-friction surface. The thick middle myocardium contains the contractile cardiac muscle arranged in layers that spiral for twisting ejection. The outer epicardium is visceral pericardium, a serous membrane secreting fluid to reduce friction against the parietal pericardium of the sac. Inflammation of these layers causes endocarditis or pericarditis, each with distinct pain and risks.