Pericardium
A conical fibro-serous sac surrounding the HEART and the roots of the great vessels (AORTA; VENAE CAVAE; PULMONARY ARTERY). Pericardium consists of two sacs, the outer fibrous pericardium and the inner serous pericardium. Serous pericardium consists of an outer parietal layer and an inner visceral layer next to the heart (epicardium) with a pericardial cavity in between.