Download The Heart

The Heart
1
Description of the Heart (Part 1)
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Heart location
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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
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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)
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Pericardial Sac
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Fibrous pericardium
Serous pericardium
• Parietal
• Visceral
• Pericardial cavity
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Cardiac Wall
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Epicardium – Visceral
pericardium
Myocardium – Muscle
layer
Endocardium – Lining
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Clinical
Applications
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CPR
Cardiac tamponade
Pericarditis
Myocarditis
Endocarditis
• Chambers
• Valves
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Gross Anatomy of the Heart (Anterior
Aspect)
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Gross Anatomy of the Heart
(Posterior Surface View)
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Description of the Heart (Part 3)
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Cardiac Chambers
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• Left
• Receives oxygen
enriched blood
from lungs
Atria
• Thin walls
• Pectinate muscle
• Separated by
• Interatrial septum
• Fossa (foramen)
ovalis
• Right
• Receives oxygen
depleted blood from
body
• Lowest blood
pressure in body
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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
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Cardiac Valves
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Structure
• Cusp
• Endocardium
• Dense connective
tissue
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Function
• Prevent reverse flow
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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
• Chordae tendinae
• Papillary muscle
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Gross Anatomy of the Heart (Frontal
Section)
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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
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Great vessels of the Heart
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Description of the Heart (Part 6)
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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)
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Specialized
myocardial cells
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Autorhythmic
Pacemaker
Conduction system
Pacemaker cells set
up basic rhythm of
contractions
Conduction system
coordinates
contraction of
myocardial fibers
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Conduction system
components
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Sinoatrial (SA) node
• In R. atrium near SVC
opening
• Primary pacemaker
• Impulse transmits to
AV node
• Maintains rhythm of
60-100 bpm
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Atrioentricular (AV)
node
• In interatrial septum
• Secondary pacemaker
• Impulse transmits to
AV bundle
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The Intrinsic Conduction of the Heart
and Succession of Action Potential
Through Selected Areas
12
Cardiac Conduction System (Part 2)
• Sets basic rhythm if
SA node is not
functioning
• Maintains rhythm of
40-50
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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
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Clinical applications
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Artificial pacemakers
Bundle branch block
• Complete
• Right
• Left
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The Sequence of Excitation of the
Heart Related to the Deflection Waves
of an ECG Tracing
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An Electrocardiogram (ECG) Tracing
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Summary of Events Occurring in the
Heart During the Cardiac Cycle
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Cardiac Cycle (Part 1)
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Events associated
with one heart beat –
Lasts about 0.8 sec
R. & L. sides
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Acts simultaneously
Develop different
pressures
Expel the same volume
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Chambers fill
passively
Atria contract while
ventricles relax
Ventricles contract
while atria relax
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Systole – Contraction
phase
Asystole – Relaxation
phase
Phases
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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
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Ventricular filling
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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)
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Ventricular systole
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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
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Factors Involved in Regulation of
Cardiac Output
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Generalizing Structure of Arteries,
Veins, and Capillaries
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