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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
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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
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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
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External Anatomy• Four chambers– 2 atria– 2 ventricles
• Major veins– Superior&
Inferior vena cava
– Pulmonary veins
• Major arteries– Aorta– Pulmonary trunk
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External anatomy: anterior
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External anatomy: posterior
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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
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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.
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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
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Histology of cardiac muscle tissue
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The chambers of the heart
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Systemic & Pulmonary Circulation
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Heart Valves• Atrioventricular
(AV)– Tricuspid– Bicuspid or
mitral
• Semilunar– Aortic– Pulmonary
• Prevent blood from flowing back
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The semilunar valves
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Location of Heart Valves
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Blood Flow Through Heart
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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
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The conduction system
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The excitation of the heart and ECG
Systole contractionDiastole RelaxationEvents of the Cardiac Cycle
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Normal Cardiac Cycle
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20-25
Cardiac Cycle
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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
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Heart MnemonicsValves TRIPS BIAS TRIcuspid
PulmonarySemilunarBIcuspidAortic Semilunar
Valves TRIPS, MI ASs(uses MItral instead of
BIcuspid)
TRIcuspidPulmonarySemilunarMItralAortic Semilunar
Valves-Atriums "LAB RATs" Left Atrium: BicuspidRight Atrium: Tricuspid
Heart valves: closure sequence
Many Things Are Possible":
Mitral, Tricuspid, Aortic, Pulmonary
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 trunkleft Common Carotidleft Subclavian
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Electrocardiogram
P wave depolarization of the atria
QRS complex depolarization of the ventricle
T wave repolarization of ventricles
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The cardiac cycle: Ventricular filling
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The cardiac cycle: Ventricular
systole
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The cardiac cycle: Isovolumetric relaxation
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Resources
• Heart Sounds & Cardiac Arrhythmias • Live Cardiac Exam Video • Anatomy Links • Cardiac Cycle • Cardiac Cycle Graphics• Interactive Physiology Review