The pericardium is an epithelialized fibrous sac that invests the heart The pericardium consists of a visceral laver that is adherent to the epicardium and a parietal layer separated from the visceral layer by a thin layer of fluid. The fluid layer provides lubrication for the continuous movement of the enclosed heart. The pericardium is nor very distensible and thus strongly resists a large, rapid increase in cardiac size. Therefore the pericardium helps prevent sudden over distention of the heart chambersThe pericardium consists of a visceral layer that is adherent to the epicardium and a parietal layer separated from the visceral layer by a thin layer of fluid. The fluid layer provides lubrication for the continuous movement of the enclosed heart. The pericardium is nor very distensible and thus strongly resists a large, rapid increase in cardiac size. Therefore the pericardium helps prevent sudden over distention of the heart chambers. The pericardium is an epithelialized fibrous sac that invests the heart