The pericardium is a fibroserous sac that surrounds the heart and roots of the great vessels. It consists of the fibrous pericardium and serous pericardium. The fibrous pericardium is a conical sac made of fibrous tissue that protects the heart. The serous pericardium is a double-layered membrane that forms the pericardial sac, with fluid allowing the heart to move smoothly. The pericardium contains the heart, vessels, and parts of the great vessels, and has transverse and oblique sinuses.