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Download The Heart Chapter 18 Part 1
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Trace the pathway of blood ( )through the body using the following terms: – – – – – – – – – – – – – Aorta Right atrium Left atrium Right ventricle Left ventricle Lungs Vena Cava Venules Arterioles Capillaries Body tissues Pulmonary artery Pulmonary vein The Heart Functions of the Heart • Generating blood pressure • Routing blood – Heart separates pulmonary and systemic circulations • Ensuring one-way blood flow – Heart valves ensure one-way flow • Regulating blood supply – Changes in contraction rate and force match blood delivery to changing metabolic needs Size, Shape, Location of Heart • Size of a closed fist • Shape – Apex: Blunt rounded point of cone – Base: Flat part at opposite of end of cone • Located in thoracic cavity in mediastinum External Anatomy • Four chambers – 2 atria – 2 ventricles • Major veins – Superior& Inferior vena cava – Pulmonary veins • Major arteries – Aorta – Pulmonary trunk External Anatomy External anatomy: anterior External anatomy: posterior Pericardium Heart Wall • Three layers of tissue – Epicardium: (aka visceral pericardium) This serous membrane of smooth outer surface of heart – Myocardium: Middle layer composed of cardiac muscle cell and responsibility for heart contracting – Endocardium: Smooth inner surface of heart chambers Myocardium • Cardiac muscle • Fibrous skeleton of the heart – Consists of four dense connective tissue rings – Prevents overstretching of the valves – Serves as a point of insertion for cardiac muscle and as an electrical insulator. Cardiac Muscle • Elongated, branching cells containing 1-2 centrally located nuclei • Contains actin and myosin myofilaments • Intercalated disks: Specialized cell-cell contact with Desmosomes and gap junctions • Electrically, cardiac muscle behaves as single unit Histology of cardiac muscle tissue The chambers of the heart Systemic & Pulmonary Circulation Heart Valves • Atrioventricular (AV) – Tricuspid – Bicuspid or mitral • Semilunar – Aortic – Pulmonary • Prevent blood from flowing back The AV valves The semilunar valves Location of Heart Valves Blood Flow Through Heart Intrinsic Conduction System • Sinoatrial node/pacemaker – Crescent shaped node in right atrium – Enforces a contraction rate of 75 beats/min • Atrioventricular node – Junction of atria and ventricles • Atrioventricular bundle/bundle of His – In interventricular septum • Purkinje fibers – Spread within the muscle of the ventricle walls The conduction system The excitation of the heart and ECG Systole contraction Diastole Relaxation Events of the Cardiac Cycle Normal Cardiac Cycle Cardiac Cycle 20-25 Heart sounds • Lup-dup, pause, lupdup, pause • First heart sound or “lubb” – Closing of AV valves at beginning of ventricular systole • Second heart sound or “dupp” – Closing of SL valves at beginning of ventricular diastole, lasts longer • Third heart sound (occasional) – Caused by turbulent blood flow into ventricles and detected near end of first one-third of diastole Heart Mnemonics Valves TRIPS BIAS TRIcuspid Pulmonary Semilunar BIcuspid Aortic Semilunar Valves TRIPS, MI ASs (uses MItral instead of BIcuspid) TRIcuspid Pulmonary Semilunar MItral Aortic Semilunar Valves-Atriums "LAB RATs" Heart valves: closure sequence Many Things Are Possible": Electrical Signal The patient's family are all having Heart attacks, you must SAVe HIS KIN!" SA node ---> AV node ---> HIS (bundle of) --> PurKINje fibers Aorta Branches Know your ABC'S: Aortic arch gives rise to: Brachiocephalic trunk left Common Carotid left Subclavian Left Atrium: Bicuspid Right Atrium: Tricuspid Mitral, Tricuspid, Aortic, Pulmonary Electrocardiogram P wave depolarization of the atria QRS complex depolarization of the ventricle T wave repolarization of ventricles The cardiac cycle: Ventricular filling The cardiac cycle: Ventricular systole The cardiac cycle: Isovolumetric relaxation Resources • • • • • • Heart Sounds & Cardiac Arrhythmias Live Cardiac Exam Video Anatomy Links Cardiac Cycle Cardiac Cycle Graphics Interactive Physiology Review