fibrous pericardium

The fibrous pericardium is the strong outer layer of the pericardium, a membranous sac that encloses the heart. It is firmly attached to the diaphragm, mediastinal pleura, and sternum, and blends with the coverings of major blood vessels like the superior vena cava and pulmonary arteries and veins.1

Inside the fibrous pericardium is a smooth, serous membrane that lines the sac and then folds back to cover the heart. This serous membrane has two layers: the parietal pericardium lining the fibrous sac and the visceral pericardium (also called the epicardium) covering the heart itself. Between these two serous layers is the pericardial cavity, which normally contains a small amount of pericardial fluid that lubricates the membranes, allowing them to glide over each other with each heartbeat.1

Inflammation of the pericardium is known as pericarditis, which can cause chest pain and, in severe cases, may lead to cardiac tamponade, a life-threatening condition where fluid buildup compresses the heart.23