The Heart - The Heart Theheartislocatedinthe...

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The Heart The heart is located in the  mediastinum, the cavity between the  lungs. The heart is tilted so that its  pointed end, the apex, points downward  toward the left hip, while the broad end,  the base, faces upward toward the right  shoulder. The heart is surrounded by  the pericardium, a sac characterized by  the following two layers: The outer fibrous pericardium  anchors the heart to the  surrounding structures. The inner serous pericardium  consists of an outer parietal layer 
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and an inner visceral layer. A  thick layer of serous fluid, the  pericardial fluid, lies between  these two layers to provide a  slippery surface for the  movements of the heart. The wall of the heart consists of three  layers: The  epicardium  is the visceral  layer of the serous pericardium. The  myocardium  is the  muscular part of the heart that  consists of contracting cardiac  muscle and noncontracting  Purkinje fibers that conduct 
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nerve impulses. Cardiac cells  (cardiomyocytes) are in this layer. The  endocardium  is the thin,  smooth, endothelial, inner lining  of the heart, which is continuous  with the inner lining of the blood  vessels. As blood travels through the heart, it  enters a total of four chambers and  passes through four valves. The two  upper chambers, the right and left atria,  are separated longitudinally by the  interatrial septum. The two lower  chambers, the right and left ventricles,  are the pumping machines of the heart 
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and are separated longitudinally by the  interventricular septum. A valve follows  each chamber and prevents the blood  from flowing backward into the chamber  from which the blood originated. Two prominent grooves are visible on 
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The Heart - The Heart Theheartislocatedinthe...

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