1.2.3 The pericardium
The pericardium is a fibrous sac which surrounds the heart, separating it from the lungs, and its function is mechanical. The heart can function normally in the absence of the pericardium, but operates more efficiently if it is present. It acts as a barrier to infection and allows free movement of the heart within the thoracic cavity. It limits the expansion of the ventricles during diastole, preventing expansion beyond their elastic limits. Disease of the pericardium limits cardiac output by causing diastolic failure, because it prevents normal filling of the atria and ventricles, particularly on the right side (see section 2.2.10).