The fibrous pericardium is the outermost layer of the pericardial membranes around the heart. It is a tough, collagenous sheet that is superficial to the parietal layer of the serous pericardium. The two are separated by a thin layer of amorphous connective tissue. Conical in shape, it fuses and is continuous with:
- inferiorly: the central tendon of the diaphragm
- superoposteriorly: the adventitial layers of all the great vessels except the inferior vena cava which enters the pericardial cavity through the diaphragm
- anteriorly: the sternopericardial ligaments
- deep: the layers of the serous pericardium over the heart
- superiorly: the pretracheal fascia
The relations of the fibrous pericardium are:
- anterior: anterior diaphragmatic surfaces of pleura except for small 'bare area' exposed by the cardiac notch where fibrous pericardium is in direct contact with inferior left half of body of sternum
- posterior, from superior to inferior: principal bronchi, oesophagus, descending aorta, posterior mediastinal surfaces of lung
- laterally: mediastinal surface of pleura, phrenic nerves and vessels
- inferiorly: diaphragm
The relatively high tensile strength of the fibrous pericardium and its firm attachments ensure that:
- it provides a relatively unyielding barrier to the overexpansion of the heart and pericardial cavity
- its shape and position is influenced by the position of the diaphragm
- it keeps the heart and great vessels roughly central within the thoracic cavity