If you think of the heart as the body's engine, then the pericardium would serve as its lubrication system, shock absorber and anchoring bolts. The pericardium is a protective sac around the heart and the roots of the major veins and arteries leading to it. The pericardium is the main reason your heart stays anchored inside the chest and doesn't grow dangerously large under pressure.

The other function of the pericardium is to provide lubrication to the heart muscle so it can pump without restriction. To accomplish this, the pericardium is actually constructed in three layers. The layer closest to the heart muscle is called the parietal pericardium. Its inner surface is very slick, allowing the heart muscle to slide easily.

There is a layer of pericardial fluid between the perietal layer and the second layer, called the epicardium or visceral pericardium. The epicardium forms a tough outer seal to contain the shock-absorbing pericardial fluid. The outermost layer of the pericardium is the fibrous pericardium. This is by far the toughest layer, charged with the task of anchoring the heart muscle and pericardial sac to the chest walls. The fibrous pericardium is the first line of defense against a severe blow to the chest.

The pericardium usually performs as well as the heart it protects, but occasionally things can go wrong. One of the most common problems associated with the pericardium is a condition called pericarditis. If the fluid contained between the epicardium and the parietal pericardium becomes infected by bacteria, cancer or another source of infection, it tends to swell. Since the inner pericardium is a closed system, the swelling pericardial sac will begin to apply pressure to the heart itself. This causes the heart to become restricted, leading to sharp pains and shortness of breath.

Some pericarditis sufferers may believe they are experiencing a heart attack, but the pain is usually more sharp and localized to the chest. Many acute pericarditis attacks resolve themselves within days or weeks, but the patient may experience more attacks in the future. Treatment of pericarditis usually involves analgesics for the pain and antibiotics for bacterial infections. More serious conditions involving the pericardium may require needle aspirations of the pericardial sac or surgical intervention. Anyone experiencing severe chest pains, especially when accompanied by fever or triggered by exertion, should be examined by a medical professional.