Pericardium

The pericardium is a double-layered fibroserous sac that surrounds the heart and the roots of the great vessels. It consists of an outer fibrous pericardium and an inner serous pericardium. The serous pericardium is further divided into a parietal layer, which lines the inner surface of the fibrous pericardium, and a visceral layer (also known as the epicardium), which is adherent to the surface of the heart. The space between the parietal and visceral layers, known as the pericardial cavity, normally contains a few serous fluid, which serves to lubricate the heart's movement within the sac.