The heart is invested in a pericardial sac with both visceral and parietal components. The visceral layer is closely adherent to the heart wall. The space within the pericardium is small and contains approximately 1-5ml serous fluid. This allows smooth movement of the heart within the pericardium during normal systole and diastole.<br> | The heart is invested in a pericardial sac with both visceral and parietal components. The visceral layer is closely adherent to the heart wall. The space within the pericardium is small and contains approximately 1-5ml serous fluid. This allows smooth movement of the heart within the pericardium during normal systole and diastole.<br> |