1. Chapter 15 Lecture PowerPoint
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2. 15.1: Introduction
The heart pumps 7,000 liters of blood through the body each day
The heart contracts 2.5 billion times in an average lifetime
The heart and all blood vessels make up the cardiovascular system
The blood vessels make up two circuits:
Pulmonary circuit
Systemic circuit

3. Systemic circuit delivers oxygen to all
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Systemic circuit delivers oxygen to all
body cells and carries away wastes.
Deoxygenated blood
Pulmonary circuit eliminates carbon
dioxide via the lungs and oxygenates the
blood.
Oxygenated blood
Oxygenated
blood pumped to
all body tissues
via aorta
Deoxygenated
blood pumped
to lungs via
pulmonary arteries O2 O2
CO2
CO2
CO2 O2
CO2 O2
CO2
CO2
CO2 O2 O2
Alveolus O2 O2
CO2
Oxygenated blood returns
to heart via pulmonary veins
Deoxygenated blood returns
to heart via venae cavae
Left atrium
Right atrium
Left ventricle
Right ventricle

4. 15.2: Structure of the Heart
The heart is a hollow, cone-shaped, muscular pump
There are four chambers:
Two atria (for blood storage)
Two ventricles (one low pressure pump and one high pressure pump)

5. Size and Location of the Heart
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The heart size varies with body size
The heart lies in the thoracic cavity
The average size of the heart is:
14 cm long
9 cm wide
The heart is:
Posterior to the sternum
Medial to the lungs
Anterior to the vertebral column
The base lies beneath the 2nd rib
The apex at the 5th intercostal space
It lays just above the diaphragm 1 2 3 4 5 cm
© McGraw-Hill Companies, Inc./Photo and dissection by Christine Eckel

6. Base of heart Sternum Heart Apex of heart Diaphragm
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Base of heart
Sternum
Heart
Apex of heart
Diaphragm

7. Coverings of the Heart
The coverings of the heart include the pericardium:
Fibrous pericardium
Visceral pericardium
Parietal pericardium
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Right lung
Left lung
Superior
vena cava
Aorta
Pulmonary trunk
Diaphragm
Auricle of left atrium
Fibrous pericardium
Auricle of right
atrium
Cut edge of
parietal pericardium
Heart (covered by
visceral pericardium)
Right
ventricle
Left ventricle
Anterior interventricular
sulcus
Pericardial cavity

8. Wall of the Heart The heart wall has three distinct layers:
Epicardium (outer layer)
Myocardium (middle layer)
Endocardium (inner layer)
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Pericardial
cavity
Parietal
pericardium
Fibrous
pericardium
Endocardium
Coronary
blood vessel
Myocardium
Epicardium
(visceral pericardium)

10. Heart Chambers and Valves
The heart is divided into four chambers:
Right atrium:
Receives blood from the:
Inferior vena cava
Superior vena cava
Coronary sinus
Right ventricle
Receives blood from the right atrium
Left atrium
Receives blood from the pulmonary veins
Left ventricle
Receives blood from the left atrium

12. c: © The McGraw-Hill Companies, Inc.
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Aorta
Superior vena cava
Left pulmonary
artery
Right pulmonary
artery
Pulmonary trunk
Left pulmonary
veins
Right pulmonary
veins
Left atrium
Right atrium
Mitral (bicuspid) valve
Chordae tendineae
Pulmonary valve
Left ventricle
Tricuspid valve
Papillary muscle
Right ventricle
Interventricular
septum
Inferior vena cava
(a)
Aorta
Superior vena cava
Left pulmonary
artery
Aortic valve
Right pulmonary
artery
Pulmonary trunk
Left pulmonary
veins
Right pulmonary
veins
Left atrium
Mitral (bicuspid)
valve
Right atrium
Opening of coronary
sinus
Chordae tendineae
Left ventricle
Tricuspid valve
Papillary muscle
Right ventricle
Interventricular
septum
Inferior vena cava
(b)
(c)
c: © The McGraw-Hill Companies, Inc.

13. 13 Right atrium Cusps of tricuspid valve Chordae tendineae
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Right
atrium
Cusps of
tricuspid
valve
Chordae
tendineae
Interventricular
septum
Papillary
muscles
Muscular
ridges
© McGraw-Hill Higher Education, Inc./University of Michigan Biomedical Communications
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© McGraw-Hill Higher Education, Inc./University of Michigan Biomedical Communications

14. Skeleton of the Heart
The fibrous rings, together with other masses of dense connective tissue in the portion of the septum between the ventricles (interventricular septum), constitute the skeleton of the heart
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Pulmonary valve
Aortic
valve
Opening of
left coronary
artery
Tricuspid
valve
Mitral valve
Fibrous skeleton
Posterior 14

15. Path of Blood Through the Heart
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Systemic
capillaries
Tissue cells
CO2
Superior
vena cava O2
Pulmonary
artery
Alveolus
CO2
CO2
Alveolar
capillaries
Alveolar
capillaries O2 O2
Alveolus
Pulmonary
veins
Right atrium
Left atrium
Tricuspid valve
Mitral valve
Pulmonary valve
Left ventricle
Right ventricle
Aortic valve
Inferior vena cava
Aorta O2
CO2
Systemic
capillaries
Tissue cells

16. Alveolar capillaries (lungs) Blood to systemic circuit
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Blood from systemic circuit
Venae cavae and
coronary sinus
Right atrium
Tricuspid valve
Right ventricle
Pulmonary valve
Pulmonary trunk
Pulmonary arteries
Alveolar capillaries (lungs)
Pulmonary veins
Left atrium
Mitral valve
Left ventricle
Aortic valve
Aorta
Blood to systemic circuit

17. Blood Supply to the Heart
The left and right coronary arteries supply blood to the tissues of the heart
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Aorta
Right coronary artery
Left coronary artery
Posterior
interventricular
artery
Anterior
interventricular
artery
Marginal
artery
Circumflex
artery
Myocardial
capillaries in
ventricular
walls
Myocardial
capillaries in
walls of right
atrium and right
ventricle
Myocardial
capillaries in
walls of left
atrium and left
ventricle
Myocardial
capillaries in
ventricular
walls
Cardiac veins
Coronary sinus
Right atrium

18. Aorta Part of aorta removed Aortic valve cusps Right coronary artery
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Aorta
Part of
aorta
removed
Aortic
valve
cusps
Right coronary
artery
Opening of
left coronary
artery

19. Anterior interventricular artery (left anterior descending artery)
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Aorta
Superior vena cava
Right pulmonary
artery
Left pulmonary artery
Pulmonary trunk
Right pulmonary
veins
Left pulmonary veins
Left auricle
Left coronary artery
Right auricle
Great cardiac vein
Right coronary
artery
Anterior interventricular artery
(left anterior descending artery)
Anterior cardiac vein
Small cardiac vein
Left ventricle
Inferior vena cava
Right ventricle
Apex of the heart
(a)
Superior vena cava
Aorta
Right pulmonary
artery
Left pulmonary artery
Left pulmonary
veins
Right pulmonary
veins
Left auricle
Circumflex artery
Cardiac vein
Left atrium
Right atrium
Inferior vena cava
Coronary sinus
Middle cardiac vein
Left ventricle
Posterior interventricular
artery
(b)
Right ventricle
Apex of the heart

20. 15.3: Heart Actions The heart chambers function in coordinated fashion
Heart actions are regulated so that atria contract (atrial systole) while ventricles relax (ventricular diastole); followed by ventricles contract (ventricular systole) while atria relax (atrial diastole)
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Pulmonary
valve closed
Aortic
valve closed
Pulmonary
valve open
Aortic
valve open RA LA
Atrial systole
Atrial diastole
Ventricular
systole
Tricuspid
and mitral
valves open LV
Tricuspid
and mitral
valves closed
Ventricular
diastole RV
(a)
(b)

21. Cardiac Cycle
During a cardiac cycle, the pressure in the heart chambers rise and falls
In atrial systole and ventricular diastole:
Blood flows passively into the ventricles
The remaining 30% of blood is pushed into the ventricles
The A-V valves open and the semilunar valves close
The ventricles relax
This causes an increase in ventricular pressure
In ventricular systole and atrial diastole:
The A-V valves close
The chordae tendinae prevent the cusps of the valves from bulging too far into the atria
The atria relax
The blood flows into atria
The ventricular pressure increases and opens the semilunar valves
The blood flows into pulmonary trunk and aorta

22. Heart Sounds
A heart beat through a stethoscope sounds like “lubb-dupp”
The “lubb”
The first heart sound
It occurs during ventricular systole
The A-V valves are closing
The “dupp”
The second heart sound
It occurs during ventricular diastole
The pulmonary and aortic semilunar valves are closing
A murmur – abnormal heart sound from the cusps not completely closing

23. Aortic area Pulmonary area Tricuspid Mitral area area
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Aortic area
Pulmonary area
Tricuspid
area
Mitral area

24. Cardiac Muscle Fibers
Cardiac muscle fibers form a functional syncytium
This is a mass of cells that function as a unit
Two such areas exist in the heart:
In the atrial walls called the atrial syncytium
In the ventricular walls called the ventricular syncytium

25. Cardiac Conduction System
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Clumps or strands of specialized cardiac muscle tissue which initiate and distribute impulses throughout the myocardium
The cardiac conduction system coordinates the events of the cardiac cycle
SA node
Atrial syncytium
Junctional fibers
AV node
AV bundle
Bundle branches
Purkinje fibers
Ventricular syncytium

26. 26 Interatrial septum Left bundle branch SA node AV node Junctional
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Interatrial septum
Left
bundle
branch
SA node
AV node
Junctional
fibers
AV bundle
Right bundle
branch
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Purkinje fibers
Interventricular
septum
Myocardial
muscle fibers
(a)
(b) 26

27. Electrocardiogram
An electrocardiogram or ECG is a recording of electrical changes that occur in the myocardium during the cardiac cycle
It is used to assess the hearts ability to conduct impulses
The deflections in the normal ECG, or waves, include:
P wave – atrial depolarization
QRS complex (three waves) – ventricular depolarization
T wave – ventricular repolarization

28. R Q S (a) 1.0 1.0 .5 .5 Millivolts Millivolts
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(a)
1.0
1.0 .5 .5
Millivolts
Millivolts
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–.5
–.5
200
400
600
200
400
600
(b)
Milliseconds
(f)
Milliseconds R
1.0
1.0 .5 .5
Millivolts
Millivolts Q
–.5
–.5
200
400
600
200
400
600 S
(c)
Milliseconds
(g)
Milliseconds
1.0
1.0 .5 .5
Millivolts P T
Millivolts
–.5
–.5
200
400
600
200
400
600
(d)
Milliseconds
(h)
Milliseconds
1.0 R .5
QRS complex
Millivolts Q
–.5 S
200
400
600
(e)
Milliseconds

29. R R P P T T Q Q S S Atrial systole Atrial diastole Atrial systole
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Atrial
systole
Atrial
diastole
Atrial
systole
Atrial
diastole
Ventricular
diastole
Ventricular
systole
Ventricular
diastole
Ventricular
systole
Ventricular
diastole
Pressure changes
0.3
0.6
0.9
seconds
120
Aortic
semilunar
Aortic semilunar
valve closes
100
valve
opens 80
Aortic pressure
Pressure (mm Hg) 60
Ventricular pressure 40
AV valve
closes
AV valve opens 20
Atrial pressure
Ventricular volume
160
Volume (mL)
120
Ventricular volume 80
Electrocardiogram (ECG) R R +1
Millivolts P P T T Q Q –1 S S
One cardiac cycle
Heart sounds
Lubb: AV
valves close
Dupp: Semilunar
valves close

30. Regulation of the Cardiac Cycle
The SA node controls the heart rate
There are also sympathetic and parasympathetic fibers that control the heart rate as well
There are also regulatory reflex centers that influence heart rate
Additional factors that may influence heart rate include:
Physical exercise
Body temperature
Concentration of various ions including:
Potassium
Calcium
Parasympathetic impulses decrease heart action
Sympathetic impulses increase heart action
Cardiac center regulates autonomic impulses to the heart

31. (transverse sections)
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Receptor
Sensory or
afferent neuron
Central
Nervous
System
Motor or
efferent neuron
Effector
(muscle or gland)
(a)
Carotid
baroreceptors
Carotid
sinus
Cerebrum
(frontal
section)
Common
carotid
artery
Sensory
fibers
Hypothalamus
Aorta
Medulla
(transverse
section)
Aortic
baroreceptors
Parasympathetic
vagus nerve
Cardiac
center
SA node
AV node
Spinal cord
(transverse sections)
Sympathetic
nerve
(b)
Sympathetic trunk