ABSTRACT
The pericardium envelops the heart and is composed of serous and fibrous layers. It is about 2 mm thick and receives oxygenated blood from the internal mammary arteries. The thin inner serous visceral pericardium is the epicardium. It covers the outer surface of the heart including the proximal great arteries, where it melds with their adventitia, and the terminal portions of the superior vena cava (SVC) and pulmonary veins and reflects back on itself as the parietal pericardium which lines the fibrous pericardium. The outer surface of the fibrous pericardium is firmly attached to the central tendinous and left muscular portions of the diaphragm, and more loosely to the sternum, costal cartilages, parietal pleurae, vertebral bodies, esophagus, and descending thoracic aorta (DAO). These attachments limit displacement of the heart. The inferior vena cava (IVC) enters the pericardium directly through the central diaphragm and is therefore not covered by the fibrous pericardium. The reflections of the serous pericardium, i.e. the junctions of visceral and parietal layers, form two prominent sinuses. The transverse sinus is a tunnel-like projection of the pericardium anterior to the SVC and atria and posterior to the great arteries. The oblique sinus is an inverted U-shaped cul-de-sac located behind the left atrium between the right and left pulmonary veins.
