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Chapter 14
The Heart
Copyright ©2014 by Elsevier Inc. All rights reserved.
Lesson 14.1
Anatomy and Blood Flow in the Heart
Discuss the location, size, and position of the heart in
the thoracic cavity and identify the heart chambers,
valves and their major disorders, and sounds.
2. Trace blood through the heart, compare the functions
of the heart chambers on the right and left sides, and
explain how a myocardial infarction might occur.
1.
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2
Location, Size, & Position of the Heart
 Triangular organ located in mediastinum with
two-thirds of the mass to the left of the body
midline and one-third to the right; the apex is
on the diaphragm
 Shape and size of a closed fist
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3
The Heart
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4
Cardiopulmonary Resuscitation (CPR)
 Heart lies between the sternum in front and the
bodies of the thoracic vertebrae behind
 Rhythmic compression of the heart between the
sternum and vertebrae can maintain blood flow
during cardiac arrest
 If combined with artificial respiration procedure,
it can be lifesaving
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5
Anatomy of the Heart
 Heart chambers
 Two upper chambers are called atria
(receiving chambers)—right and left
atria
 Two lower chambers called
ventricles (discharging chambers)—
right and left ventricles
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Heart Chambers
Wall of each heart chamber is composed
of cardiac muscle tissue called
myocardium
 Endocardium—smooth lining of heart
chambers

• Inflammation of endocardium is called
•
endocarditis
Inflamed endocardium can become rough and
abrasive and thereby cause a thrombus
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The Pericardium and Pericarditis
 Pericardium—two-layered fibrous sac with a
lubricated space between the two layers
 Inner layer is called visceral pericardium or
epicardium
 Outer layer called parietal pericardium
 Pericarditis—inflammation of the pericardium
 Cardiac tamponade—compression of the heart
caused by fluid building up between the visceral
pericardium and parietal pericardium
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8
An Internal View of the Heart
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Heart Action
 Contraction
of the heart is called
systole
 Relaxation of the heart is called
diastole
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10
Heart
Action
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Heart Valves
Valves keep blood flowing through the heart;
prevent backflow
 Atrioventricular (AV) valves

Tricuspid—at the opening of the right atrium into
the ventricle
 Bicuspid (mitral) —at the opening of the left
atrium into the ventricle

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Semilunar (SL) Valves
 Pulmonary semilunar—at the
beginning of the pulmonary artery
 Aortic semilunar—at the
beginning of the aorta
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Valve Disorders
 Incompetent valves “leak,” allowing some blood
to flow backward into the chamber from which it
came
 Stenosis- valves are narrower than normal,
reducing blood flow
 Rheumatic heart disease—cardiac damage
resulting from a delayed inflammatory response
to streptococcal infection
 Mitral valve prolapse (MVP)—incompetence
of mitral valve caused by its edges extending
back into the left atrium when the left ventricle
contracts
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14
Mitral Valve Stenosis
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Mitral Valve Prolapse
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Heart Sounds
 Two distinct heart sounds in every heartbeat, or
cycle—“lub-dup”
 First sound (lub) caused by the vibration and
closure of AV valves during contraction of the
ventricles
 Second sound (dup) caused by the closure of
the semilunar valves during relaxation of the
ventricles
 Heart murmurs—abnormal heart sounds often
caused by abnormal valves
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17
Blood Flow Through the Heart
 Heart acts
as two separate pumps—
the right atrium and ventricle
performing different functions from
the left atrium and ventricle
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Blood Flow Through the Cardiovascular System
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Sequence of Blood Flow
 Venous blood enters the right atrium through the
superior and inferior venae cava—passes from the right
atrium through the tricuspid valve to the right ventricle
 From the right ventricle through the pulmonary
semilunar valve to the pulmonary artery to the lungs—
blood from the lungs to the left atrium, passes through
the bicuspid (mitral) valve to left ventricle
 Blood in the left ventricle is pumped through the aortic
semilunar valve into the aorta and is distributed to the
body as a whole
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Coronary Circulation


Blood, which supplies oxygen and nutrients to
the myocardium of the heart, flows through the
right and left coronary arteries
Blockage of blood flow through the coronary
arteries can cause myocardial infarction (heart
attack)
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21
Coronary Circulation
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Blood vessels that supply the myocardium
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Coronary Heart Disease
 Coronary thrombosis
and coronary embolism
involve a blood clot
blocking some part of a
coronary artery
 Blood cannot flow
through to the heart, and
those cells start to die
 Myocardial infarction
(MI), or tissue death,
occurs
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Coronary Heart Disease, Cont'd.
 Atherosclerosis—type of “hardening of arteries” in
which lipids build up on the inside wall of blood vessels;
can partially or totally block coronary blood flow
 Angina pectoris—chest pain caused by inadequate
oxygen to the heart
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Treatment of Heart Disease
Coronary angioplasty.
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Treatment of Heart Disease (cont.)
Arterial stent.
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Coronary Bypass Surgery
 Common treatment for patients with severely
restricted coronary artery blood flow
 Other veins or vessels are taken from the body and
used to bypass blockages in the coronary arteries
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Prevention of Coronary Artery
Disease
Risk Factors for Coronary Artery Disease
Risk Factors
That
Cannot Be Modified
Risk Factors
That Can
Be Modified
Age
Smoking and other forms of tobacco use
Gender
Physical inactivity
Heredity
Overweight
Body type
Saturated fat in diet
Hypertension
Type 2 diabetes
Sleep apnea
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Cardiac Cycle
 Heartbeat is regular and
rhythmical—each complete beat
called a cardiac cycle—average is
about 72 beats per minute
 Each cycle, about 0.8 seconds long,
subdivided into systole
(contraction phase) and diastole
(relaxation phase)
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Conduction System of the Heart

Normal structure and function
• SA (sinoatrial) node, the pacemaker—located in the
•
•
•
wall of the right atrium near the opening of the
superior vena cava
AV (atrioventricular) node—located in the right
atrium along the lower part of the interatrial septum
AV bundle (bundle of His) —located in the septum
of the ventricle
(subendocardial fibers)—located in the walls of
Purkinje fibers the ventricles
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Conduction System of the Heart
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Conduction System of the Heart
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Electrocardiography



Specialized conduction system structures generate
and transmit the electrical impulses that result in
contraction of the heart
These tiny electrical impulses traveling through
the heart's conduction system can be picked up on
the surface of the body and transformed into
visible tracings by a machine called an
electrocardiograph
The visible tracing of these electrical signals is
called an electrocardiogram, or ECG or EKG
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ECG Deflections
 Electrocardiography
 The normal ECG has three deflections or
waves



P wave—associated with depolarization of the
atria
QRS complex—associated with depolarization
of the ventricles
T wave—associated with repolarization of the
ventricles
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Events Represented by the
Electrocardiogram (ECG)
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Events Represented by the
Electrocardiogram (ECG)
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Cardiac Dysrhythmia
 Abnormality of
heart rhythm
• Heart block—conduction of impulses is
blocked
• Complete heart block—impaired AV node
conduction, producing complete
dissociation of P waves from QRS complexes
• Can be treated by implanting an artificial
pacemaker
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Dysrhythmia
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Types of Dysrhythmia
 Bradycardia—slow heart rate (less than 60
beats/min)
 Tachycardia—rapid heart rate (more than 100
beats/min)
 Sinus dysrhythmia—variation in heart rate during
breathing cycle
 Premature contraction (extrasystole)—contraction
that occurs sooner than expected in a normal rhythm
 Fibrillation—condition in which cardiac muscle
fibers are “out of step,” producing no effective
pumping action
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Fibrillation
 Atrial fibrillation—(AF or A-fib) occurs in
mitral stenosis, rheumatic heart disease, and
infarction of atrial myocardium
 Ventricular fibrillation—(VF or V-fib) is lifethreatening; occurs when a lack of ventricular
pumping stops blood flow to vital tissues
 Defibrillation—can treat fibrillation by
applying an electric shock to force cardiac fibers
back into rhythm
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AEDs and Atrial Ablation
 Automatic external defibrillators (AEDs) are
small, lightweight devices that detect heart
rhythms and can produce a shock, if necessary
 Atrial ablation is used to treat atrial
fibrillation by destroying heart muscle in a
specific location and eliminating the pathway
of abnormal electrical signals
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Stroke Volume and Cardiac Output




Stroke volume is the volume of blood ejected from one
ventricle with each beat
Cardiac output (CO) is amount of blood that one
ventricle can pump each minute—average is about 5 L
per minute at rest
CO is determined by heart rate (HR) and stroke
volume (SV)
HR (beat/min) x SV (volume/beat) = CO (volume/min)
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Heart Rate (HR)
 Autonomic nervous system (ANS) can alter the heart's
rhythm to increase or decrease HR
 When blood CO2 levels rise due to exercise, HR rises to
restore homeostasis of blood gases
 Sudden drop in blood pressure can increase HR to
restore normal blood flow
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Stroke Volume (SV)
 The volume of blood ejected by the ventricles is
determined by the volume of blood returned to the
heart by the veins, or venous return
 The higher the venous return, the higher the SV
 Strength of myocardial contraction also helps determine
SV
 Valve disorders, coronary artery blockage, or myocardial
infarction can all decrease stroke volume and may
decrease cardiac output
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Cardiac Output
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Heart Failure
 Heart failure—inability to pump enough
returned blood to sustain life; it can be
caused by many different heart diseases
 Right heart failure—failure of the right
side of the heart to pump blood, usually
because the left side of the heart is not
pumping effectively
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Cor Pulmonale
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Heart Failure
 Left heart failure (congestive heart failure,
CHF)—inability of the left ventricle to pump
effectively, resulting in congestion of the
systemic and pulmonary circulations
 Diseased hearts can be replaced by donated
living hearts (transplants) or by artificial hearts
(implants), although both procedures have yet
to be perfected
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Heart Transplant
Courtesy Patricia Kane, Indiana University Medical School.
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