pericardium

(per″ĭ-kard′ē-ŭm)

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[peri- + -cardium]
The membranous fibroserous sac enclosing the heart and the bases of the great vessels. It has three layers: the fibrous pericardium (the outer layer); the parietal pericardium, a serous membrane that lines the fibrous pericardium; and the visceral pericardium (epicardium), a serous membrane on the surface of the myocardium. The space between the two serous layers is the pericardial cavity, a potential space filled with serous fluid that reduces friction as the heart beats. Its base is attached to the diaphragm, its apex extending upward as far as the first subdivision of the great blood vessels. It is attached in front to the sternum, laterally to the mediastinal pleura, and posteriorly to the esophagus, trachea, and principal bronchi.
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PERICARDIUM AND LAYERS OF THE HEART WALL

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