The pericardium is a 'sack' around the heart
Technically the pericardium has 2 layers . The visceral layer that lies against the heart and the parietal layer that is on the out side of the heart. There is a small amt of fluid in between. This protects the heart and acts as a physical barrier.Also acts as a buffer for the heart and insulates it. It can become inflamed and is called pericarditis.