ABSTRACT
The pericardium is composed of an outer fibrous layer and an inner serous membrane. The serous sac is divided into (a) a visceral pericardium, which consists of one layer of mesothelial cells and is closely applied to the epicardial surface of the heart and (b) a parietal pericardium, which lines the inside of the fibrous layer and extends to cover portions of the proximal great vessels. A potential space can exist between the serosal layers and may normally contain about 15 to 50 cm3 of fluids. This pericardial fluid is an ultrafiltrate of plasma, with protein content about one-third that of plasma. The posterior pericardial reflection about the pulmonary veins and inferior vena cava forms an inverted U-shaped pocket called the oblique pericardial sinus.
