The Hear1 - . Within the pericardial sac on the surface of...

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The Heart The heart is the muscular organ that pumps blood throughout the body. It is located in the thoracic cavity between the lungs. It is somewhat triangular in shape with the base of the heart located superiorly and the apex tilting to the left inferiorly. Walls The heart is surrounded by a membranous structure known as the pericardial sac. The pericardial sac provides room to expand during the cardiac cycle and protects the heart by resisting excessive expansion. The pericardial fluid that fills the space between the layers of the pericardial sac allows the heart to beat without friction. The outer fibrous layer of the pericardial sac is actually two structures -- a tough outer fibrous structure (which can be thought of as the "wall" of the pericardial cavity) and an inner smooth layer known as the parietal pericardium
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Unformatted text preview: . Within the pericardial sac on the surface of the heart is another serous membrane known as visceral pericardium . The visceral pericardium is synonymous with epicardium. Pericardial fluid is between the parietal and visceral pericardia. The major tissue of the heart is cardiac muscle and forms the myocardium . Forming the framework of the myocardium is a fibrous skeleton that enables the myocardium to twist during contraction, increasing the efficacy of ventricular emptying. The skeleton also insulates the atria from the ventricles during action potentials . The innermost smooth layer of the heart is endocardium . The smoothness of the endocardium enables blood to flow smoothly through the chambers of the heart. (See Figure 3). Figure 3...
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