1 the heart. 2 description of the heart (part 1) heart location ventral cavity – thoracic cavity...
TRANSCRIPT
2
Description of the Heart (Part 1)
Heart location Ventral cavity – Thoracic cavity
– Mediastinal cavity – Pericardial cavity
2/3 shifted left Extends from rib 2 to 5th
intercostal space Apex
• Left ventricle• Points toward left hip
Base • Upper posterior surface• Predominantly left atrium
Sternocostal surface Diaphragmatic surface Individual’s heart is about the
size of the person’s closed fist
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Description of the Heart (Part 2)
Pericardial Sac Fibrous pericardium Serous pericardium
• Parietal• Visceral
• Pericardial cavity
Cardiac Wall Epicardium – Visceral
pericardium Myocardium – Muscle
layer Endocardium – Lining
• Chambers• Valves
Clinical Applications CPR Cardiac tamponade Pericarditis Myocarditis Endocarditis
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Description of the Heart (Part 3)
Cardiac Chambers Atria
• Thin walls• Pectinate muscle• Separated by
• Interatrial septum• Fossa (foramen)
ovalis• Right
• Receives oxygen depleted blood from body
• Lowest blood pressure in body
• Left• Receives oxygen
enriched blood from lungs
Ventricles• Thick walls• Trabeculae carnae• Separated by –
Interventricular septum
• Right• Receives blood
from R. Atrium
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Description of the Heart (Part 4)
• Pumps blood to lungs• Left
• Receives blood from L. atrium
• Pumps blood to body• Highest blood
pressure
Cardiac Valves Structure
• Cusp• Endocardium• Dense connective
tissue• Chordae tendinae• Papillary muscle
Function• Prevent reverse flow
Location & surface projection
• Tricuspid• R. atrioventricular
valve• R./L. 5th intercostal
space, near sternum• Pulmonary semilunar
• R. ventricle pulmonary trunk
• L., 2nd intercostal space near sternum
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Description of the Heart (Part 5)
• Bicuspid (mitral)• L. atrioventricular • L., 5th intercostal space in midclavicular line
• Aortic semilunar• L. ventricle aorta• R., 2nd intercostal space, near sternum
Great vessels of the Heart
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Description of the Heart (Part 6)
Inferior vena cava (IVC) Coronary sinus Superior vena cava (SVC) Pulmonary trunk – Right ventricle Pulmonary veins – Left atrium Aorta – Left ventricle
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Cardiac Conduction System (Part 1)
Specialized myocardial cells Autorhythmic Pacemaker Conduction system
Pacemaker cells set up basic rhythm of contractions
Conduction system coordinates contraction of myocardial fibers
Conduction system components Sinoatrial (SA) node
• In R. atrium near SVC opening
• Primary pacemaker• Impulse transmits to AV
node• Maintains rhythm of 60-
100 bpm Atrioentricular (AV) node
• In interatrial septum• Secondary pacemaker• Impulse transmits to AV
bundle
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Cardiac Conduction System (Part 2)
• Sets basic rhythm if SA node is not functioning
• Maintains rhythm of 40-50
Atrioventricular bundle (Bundle of His)
• Electrically links atria to ventricles
• In septa• Impulse transmits to
bundle branches• Maintains rhythm of
20-40
R.&L. bundle branches In interventricular septum Impulses transmit to
myoconduction fibers Conduction myofibers
(Pukinje fibers)• In ventricular walls• Impulses transmit to
ventricular walls Clinical applications
Artificial pacemakers Bundle branch block
• Complete• Right • Left
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Cardiac Cycle (Part 1)
Events associated with one heart beat – Lasts about 0.8 sec
R. & L. sides Acts simultaneously Develop different
pressures Expel the same volume
Chambers fill passively Atria contract while
ventricles relax Ventricles contract while
atria relax
Systole – Contraction phase
Asystole – Relaxation phase
Phases Relaxation (Quiescent)
period• At end of heart beat –
lasts about 0.4 sec• All 4 chambers relaxed –
Pressure drops backflow of blood
• Trapped by closing of semilunar cusps of vavles – Dicrotic notch
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Cardiac Cycle (Part 2)
• All 4 valves closed – Isovolumetric relaxation• Ventricular pressure < atrial pressure – AV
valves open Ventricular filling
• Rapid ventricular filling – Passive • Diastasis• Atrial systole – Final 30mL – 0.1 sec• End diastolic volume (EDV) – about 130 mL
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Cardiac Cycle (Part 3)
Ventricular systole• AV valves shut – 1st heart sound• All 4 valves closed – Isovolumetric contraction• Ventricular pressure rises• Semilunar valves open• Ventricular ejection – 0.5 sec• Semilunar valves close – 2nd heart sound• Systole begins• End systolic volume (ESV) – 60 mL
Stroke volume = EDV –ESV Cardiac output = stroke volume x heart rate