the fibrous sac covering of the heart which is in contact with the pleura is the
Pericardium The pericardium is a double-walled sac containing the heart and the roots of the great vessels. The pericardial sac has two layers, a serous layer and a fibrous layer. It encloses the pericardial cavity which contains pericardial fluid.
Pericardium The serous pericardium, in turn, is divided into two layers, the parietal pericardium, which is fused to and inseparable from the fibrous pericardium, and the visceral pericardium, which is part of the epicardium. Both of these layers function in lubricating the heart to prevent friction during heart activity.