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Unformatted text preview: The Heart: A Two Sided Pump Cardiac Muscle involuntary striated have only a single centrally located nuclei exhibit branching Consist of two separate networks:atria and ventricles fibers in each network are connected to each other via intercalated disks (irregular transverse thickening of the sarcolemma). the discs contain gap junctions , which conduct muscle action potentials from one fiber to the other. This enables each network to conduct as a unit. This is the tricuspid valve. The leaflets and thin and delicate. Just like the mitral valve, the leaflets have thin chordae tendineae that attach the leaflet margins to the papillary muscles of the ventricular wall below. The aortic valve shows three thin and delicate cusps. The coronary artery orifices can be seen just above. The endocardium is smooth, beneath which can be seen a red- brown myocardium. The aorta above the valve displays a smooth intima with no atherosclerosis. This is a mechanical valve prosthesis of the older ball and cage variety. Such mechanical prostheses will last indefinitely from a structural standpoint, but the patient requires continuing anticoagulation because of the exposed non-biologic surfaces. The superior aspect (here the left atrium) is seen at the left, while the outflow is at the right into the left ventricle in this mitral valve prosthesis. This is a mechanical valve prosthesis of the more modern tilting disk variety. Such mechanical prostheses will last indefinitely from a structural standpoint, but the patient requires continuing anticoagulation because of the exposed non-biologic surfaces. The superior aspect (here the left atrium) is seen at the left, while the outflow, with the two leaflets tilted outward toward the left ventricle, is at the right in this mitral valve prosthesis. Normal Coronary Artery This is a normal coronary artery with a nice, big, unobstructed lumen for supplying plenty of blood to the myocardium. Serial Section of Coronary Artery This coronary artery opened longitudinally demonstrates severe atherosclerosis This is thrombosis in a coronary artery. Such a thrombus severely narrows or occludes the lumen and can produce a sudden ischemic event. &quot;Sudden death&quot; as well as infarction can occur. Risk Factors in Heart Disease Hypercholesterolemia Hypertension Cigarette smoking Obesity Lack of exercise Diabetes mellitus Genetic predisposition Male gender Alcohol Atherosclerosis of the aorta w/ mural thrombi Abdominal Aortic Aneurysm This aorta has been opened longitudinally to reveal an area of fairly limited dissection that is organizing. The red-brown thrombus can be seen in on both sides of the section as it extends around the aorta. The intimal tear would have been at the left. This creates a &quot;double lumen&quot; to the aorta. This aorta shows severe atherosclerosis which, along with cystic medial necrosis and hypertension, is a risk factor for dissection....
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- Spring '06