As ventricles contract blood forces against av valves

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As ventricles contract, blood forces against AV valves and they close AV valves closing, semilunar valves open 20
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As ventricles relax, the semilunar valves close and blood is propelled to the body 21
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Clinical Two conditions severely weaken heart: Incompetent valve Blood backflows so heart repumps same blood over and over Valvular stenosis Stiff flaps that constrict opening Heart needs to exert more force to pump blood Defective valve can be replaced with mechanical, animal, or cadaver valve 22
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Systemic & pulmonary circuits Systemic circuit L side of heart circulates oxygenated blood to body tissues & deoxygenated blood from tissues to R side of heart Pulmonary circuit R side of the heart circulates deoxygenated blood to lungs & oxygenated blood to L side of heart 23
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Coronary Circulation Coronary circulation Functional blood supply to heart muscle itself Shortest circulation in body Delivered when heart is relaxed Left ventricle (thicker than right) receives most of coronary blood supply 24
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Coronary circuit Deliver blood to the myocardium Blockage = tissue death & heart attack (myocardial infarction) Arteries R & L coronary artery from the base of aorta R coronary artery: R side of the heart L coronary artery: L side of the heart Veins Cardiac veins join together to coronary sinus, empties blood from myocardium into right atrium Then back to R atrium 25
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Pathway of Blood Through Heart Equal volumes of blood are pumped to pulmonary and systemic circuits Pulmonary circuit is short, low-pressure circulation Systemic circuit is long, high-friction circulation Anatomy of ventricles reflects differences Left ventricle walls are thicker than right Pumps with greater pressure 26
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Figure 18.9 Anatomical differences between the right and lef ventricles. Right ventricle Left ventricle Interventricular septum ***Check the thickness of left ventricle 27
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Quiz yourself! (Home work) Trace a drop of blood through the pulmonary circuit and systemic circuit, including names of the valves. Be sure to include: Oxygenated blood from lungs; Deoxygenated blood (from tissues) 4 chambers 4 valves Superior/inferior vena cava Pulmonary trunk, arteries, veins Aorta Capillary bed/tissues Know the path, must for exam*** 28
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Quiz yourself! (Home work) List the similarities and differences between: 1. Tricuspid and mitral valves 2. Atrioventricular and semilunar valves 29
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Myocardial infarction (heart attack) Prolonged coronary blockage Areas of cell death are repaired with noncontractile scar tissue 30
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Cardiac muscle: microscopic anatomy Skeletal muscle Multinucleate Long/cylindrical Lack junctions Cardiac muscle Uni-nucleate Fat/branched fibers Intercalated discs - CONTAIN DESMOSOMES & GAP JUNCTIONS - DESMOSOMES KEEP CELLS TOGETHER WHEN CONTRACTING - GAP JUNCTIONS LET IONS PASS BETWEEN CELLS TO TRANSMIT ELECTRICAL SIGNAL ACROSS ENTIRE MUSCLE 31
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Table 18.1 Key Differences between Skeletal and Cardiac Muscle 32
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Christopher Reinemann
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