<P> The pericardium fixes the heart to the mediastinum, gives protection against infection, and provides the lubrication for the heart . </P> <P> The pericardium is a tough double layered fibroserous sac which covers the heart . The space between the two layers of serous pericardium (see below), the pericardial cavity, is filled with serous fluid which protects the heart from any kind of external jerk or shock . There are two layers to the pericardial sac: the outermost fibrous pericardium and the inner serous pericardium . </P> <P> The fibrous pericardium is the most superficial layer of the pericardium . It is made up of dense and loose connective tissue, which acts to protect the heart, anchoring it to the surrounding walls, and preventing it from overfilling with blood . It is continuous with the outer adventitial layer of the neighboring great blood vessels . </P> <P> 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 . </P>

Inner lining of the fibrous pericardium is formed by