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Marieb Chapter 18 Part A: The Heart
CABG
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How Hard Does Our Heart Work?
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Pulmonary
trunk
Pericardium
Myocardium
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Fibrous pericardium
Parietal layer of
serous pericardium
Pericardial cavity
Epicardium
(visceral layer Heart
of serous
wall
pericardium)
Myocardium
Endocardium
Heart chamber
Figure 18.2
Layers of the Heart Wall
1.
Epicardium — visceral layer of the serous pericardium
2.
Myocardium - contractile muscle and conduction system
•
3.
Fibrous skeleton of the heart: crisscrossing, interlacing layer of
connective tissue
•
Anchors cardiac muscle fibers
•
Supports great vessels and valves
•
Limits spread of action potentials to specific paths (nonconductive)
•
Provides a framework so muscles don’t affect each other
when they contract
Endocardium is continuous with blood vessel endothelium
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Brachiocephalic trunk
Superior vena cava
Right pulmonary
artery
Ascending aorta
Pulmonary trunk
Right pulmonary
veins
Right atrium
Right coronary artery
(in coronary sulcus)
Anterior cardiac vein
Right ventricle
Right marginal artery
Small cardiac vein
Inferior vena cava
(b) Anterior view
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Left common carotid
artery
Left subclavian artery
Aortic arch
Ligamentum arteriosum
Left pulmonary artery
Left pulmonary veins
Auricle of
left atrium
Circumflex artery
Left coronary artery
(in coronary sulcus)
Left ventricle
Great cardiac vein
Anterior interventricular
artery (in anterior
interventricular sulcus)
Apex
Figure 18.4b
Aorta
Superior vena cava
Right pulmonary
artery
Pulmonary trunk
Right atrium
Right pulmonary
veins
Fossa ovalis
Pectinate muscles
Tricuspid valve
Right ventricle
Chordae tendineae
Trabeculae carneae
Inferior vena cava
Left pulmonary
artery
Left atrium
Left pulmonary
veins
Mitral (bicuspid)
valve
Aortic valve
Pulmonary valve
Left ventricle
Papillary muscle
Interventricular
septum
Epicardium
Myocardium
Endocardium
(e) Frontal section
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Figure 18.4e
Two Circuits
Pulmonary
Circuit
Pulmonary arteries
Venae cavae
Capillary beds
of lungs where
gas exchange
occurs
Pulmonary veins
Aorta and branches
Left atrium
Left ventricle
Right atrium
Right ventricle
Oxygen-rich,
CO2-poor blood
Oxygen-poor,
CO2-rich blood
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Heart
Systemic
Circuit
Capillary beds of all
body tissues where
gas exchange occurs
Figure 18.5
Pathway of Blood Through Circuits
• Equal volumes of blood are pumped to the
pulmonary and systemic circuits
• Pulmonary circuit is a short, low-pressure
circulation
• Systemic circuit blood encounters much
resistance in the long pathways
• Anatomy of the ventricles reflects these
differences (LV size >>> RV size)
• Coronary circuit is a part of the
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Left
ventricle
Right
ventricle
Interventricular
septum
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Figure 18.6
Coronary Circuit
• The functional blood supply to the heart muscle itself
• Arteries connect to other arteries via anastomoses
(junctions) (ex: R and L coronary circulations)
• On surface:
• In the muscle:
• RT coronary artery serves:
• L coronary artery serves:
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Superior
vena cava
Anastomosis
(junction of
vessels)
Right
atrium
Aorta
Pulmonary
trunk
Left atrium
Left
coronary
artery
Circumflex
artery
Right
coronary
Left
artery
ventricle
Right
ventricle
Anterior
Right
interventricular
marginal Posterior
artery
artery
interventricular
artery
(a) The major coronary arteries
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Figure 18.7a
Superior
vena cava
Anterior
cardiac
veins
Great
cardiac
vein
Coronary
sinus
Small cardiac vein
Middle cardiac vein
(b) The major cardiac veins
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Figure 18.7b
Aorta
Left pulmonary
artery
Superior vena cava
Left pulmonary
veins
Auricle of left
atrium
Left atrium
Great cardiac
vein
Right pulmonary veins
Posterior vein
of left ventricle
Left ventricle
Apex
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Right pulmonary artery
Right atrium
Inferior vena cava
Coronary sinus
Right coronary artery
(in coronary sulcus)
Posterior
interventricular
artery (in posterior
interventricular sulcus)
Middle cardiac vein
Right ventricle
(d) Posterior surface view
Figure 18.4d
Homeostatic Imbalances
• Angina pectoris
• Occurs because of atherosclerosis in coronary arteries
• Emotion, physical stress, etc. cause HR and
contractility to increase
• Clogged arteries can’t meet the demand for oxygen
and nutrients
• Thoracic pain results
• Stop activity, take a vasodilator; pain subsides
• No cell death because it is a temporary situation
• Sign of CAD
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Homeostatic Imbalances
• Myocardial infarction (heart attack)
• Prolonged coronary blockage
• Plaque alone
• Plaque + clot
• Plaque embolizes
• Vessel spasm
• Areas of cell death are repaired with noncontractile scar tissue
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What Happens After A MI?
• Dead cells are replaced by non-contractile
scar tissue (collagen)
•Non-contractile
•Non-conductive
•Stiffens the heart
• If the heart attack is severe, the heart might go into
ventricular fibrillation or not pump well enough
to maintain the perfusion of tissues and BP
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What Does a MI Look Like?
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Heart Valves
• Ensure unidirectional blood flow through the heart
• Valves can be damaged by
• Types of damage
• Incompetence/insufficiency
• Stenosis
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Heart Valves
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Myocardium Pulmonary valve
Aortic valve
Tricuspid
Area of cutaway
(right atrioventricular)
Mitral valve
valve
Tricuspid valve
Mitral
(left atrioventricular)
valve
Aortic
valve
Myocardium
Tricuspid
(right atrioventricular)
valve
Mitral
(left atrioventricular)
valve
Aortic valve
Pulmonary
valve
Fibrous
skeleton
(a)
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Pulmonary valve
Aortic valve
Area of cutaway
(b)
Pulmonary
valve
Mitral valve
Tricuspid
valve
Anterior
Figure 18.8a
Microscopic Anatomy of Cardiac Muscle
Nucleus
Intercalated discs
Gap junctions
(a)
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Cardiac muscle cell
Desmosomes
Microscopic Anatomy of Cardiac Muscle
• Intercalated discs: junctions between cells
anchor cardiac cells
• Desmosomes prevent cells from separating
during contraction
• Gap junctions allow ions to pass; electrically
couple adjacent cells
• Heart muscle behaves as a functional
syncytium (
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)