The cavity between the parietal and visceral layers is the pericardial cavity which contains pericardial fluid.

The Heart wall is composed of 3 layers:

• Epicardium - the outer layer of the heart wall (also called the visceral pericardium).
• Myocardium - thick middle layer composed of cardiac muscle.
• Endocardium - thin inner layer lining the cavities of the heart, valves and muscles.