1. © 2012 Pearson Education, Inc.
21
The Cardiovascular
System: The Heart
PowerPoint® Lecture Presentations prepared by
Steven Bassett
Southeast Community College
Lincoln, Nebraska

2. Introduction
The blood must stay in motion to maintain
homeostasis.
 The heart keeps blood moving.
The volume of blood pumped by the heart
can vary widely, between 5 and 30 liters per
minute.
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3. An Overview of the Cardiovascular System
The heart is a small organ; your heart is roughly the size of your
clenched fist.
Two closed circuits:
 Pulmonary circuit carries carbon dioxide—rich blood from the
heart to the lungs and back
 Systemic circuit transports oxygen-rich blood from the heart to
the rest of the body and back
The heart has four muscular chambers:
 Right and left atria collect blood returning to heart
 Right and left ventricles discharge blood into vessels to leave
the heart.
 Left ventricle is considered the strongest chamber of the heart and creates
the highest pressure in the circulation.
 Right ventricle contains the “Moderator band”.
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4. Figure 21.2a Location of the Heart in the Thoracic Cavity
Trachea
Right lung
Anterior view of the open chest cavity showing the position
of the heart and major vessels relative to the lungs. The
sectional plane indicates the orientation of part (c).
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Apex of
heart
Parietal pericardium
(cut)
Base of
heart
Diaphragm
Thyroid gland
First rib (cut)
Left lung

5. An Overview of the Cardiovascular System
 Pulmonary circuit
 Right atrium
 Tricuspid valve
 Right ventricle
 Pulmonary valve
 Pulmonary
trunk/pulmonary
arteries.
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 Systemic circuit
 Left atrium
 Mitral valve
 Left ventricle
 Aortic valve
 Aorta

6. © 2012 Pearson Education, Inc.
CIRCULATIONS

7. The Pericardium
The pericardium is the serous membrane
lining the pericardial cavity, which surrounds
the heart
 Visceral pericardium (epicardium) covers the
heart’s outer surface
 Parietal pericardium lines the inner surface of
the pericardial sac
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8. Figure 21.2b Location of the Heart in the Thoracic Cavity
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Relationships between the heart and the pericardial
cavity. The pericardial cavity surrounds the heart
like the balloon surrounds the fist (right).
Pericardial
cavity containing
pericardial fluid
Cut edge of
parietal pericardium
Cut edge of
epicardium
(visceral pericardium)
Fibrous attachment
to diaphragm
Air space
(corresponds
to pericardial
cavity)
Balloon

9. Structure of the Heart Wall
Three distinct layers:
 Epicardium — covers the outside of the heart
 Myocardium — cardiac muscle, the thickest
layer of the heart.
 The muscular ridges in the inner surface of the atria
are called Pectinate muscles.
 Microscopic appearance of cardiac muscle shows
branched fibers and intercalated discs.
 Endocardium — lines the inside of the heart
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10. Figure 21.3de Histological Organization of Muscle Tissue in the Heart Wall
Diagrammatic three-dimensional
view of cardiac muscle cells
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The structure of an intercalated disc
Cardiac muscle cell
Mitochondria
Intercalated
disc (sectioned)
Nucleus
Cardiac muscle
cell (sectioned)
Bundles of
myofibrils
Intercalated
Intercalated
disc
disc
Gap junction
Z lines bound
to opposing cell
membranes
Desmosomes

11. Orientation and Superficial Anatomy of Heart
The heart lies slightly to the left of the
midline.
 The heart sits at an oblique angle to the
longitudinal axis of the body.
 The heart is rotated slightly toward the left.
 The heart has external sulci that mark
internal boundaries.
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12. Figure 21.4 Position and Orientation of the Heart
Base of heart
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Ribs
Apex
of heart
Superior
border
Right
border Left
Inferior border
border
1 1
2 2
3 3
4 4
5 5
6 6
7 7
8
8
9 9
10 10

13. Figure 21.5a Superficial Anatomy of the Heart, Part I
Left common carotid artery
Brachiocephalic trunk
Ascending
aorta
Superior
vena cava
Auricle
of right
atrium
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Left subclavian artery
Arch of aorta
Anterior view of the heart and great
vessels
Ligamentum
arteriosum
Descending
aorta
Left pulmonary
artery
Pulmonary
trunk
Fat in
anterior
interventricular
sulcus
LEFT
VENTRICLE
RIGHT
VENTRICLE
RIGHT
ATRIUM
Fat in
coronary
sulcus
Auricle of
left atrium

14. Figure 21.5b Superficial Anatomy of the Heart, Part I
Left pulmonary artery
Left pulmonary veins
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LEFT
ATRIUM
Posterior view of the heart and great
vessels
LEFT
VENTRICLE
Fat in
coronary
sulcus
Coronary
sinus
RIGHT
VENTRICLE
RIGHT
ATRIUM
Arch of aorta
Right pulmonary
artery
Superior
vena cava
Right
pulmonary
veins (superior
and inferior)
Inferior
vena cava
Fat in posterior
interventricular sulcus

15. Orientation and Superficial Anatomy of Heart
• The left and right atria
• Positioned superior to the coronary sulcus
• Both have thin walls
• Both consist of expandable extensions called
auricles
• The left and right ventricles
• Positioned inferior to the coronary sulcus
• Much of the right ventricle forms the
diaphragmatic surface
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16. Figure 21.6a Superficial Anatomy of the Heart, Part II
RIGHT
VENTRICLE
RIGHT
ATRIUM
Ascending
aorta
Parietal
pericardium
Superior
vena cava
Auricle of
right atrium
Right coronary
artery
Coronary sulcus
Parietal pericardium fused to diaphragm
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In this photo, the pericardial sac has been
cut and reflected to expose the heart and
great vessels.
LEFT
VENTRICLE
Marginal branch
of right
coronary artery
Fibrous
pericardium
Pulmonary
trunk
Auricle of
left atrium
Anterior
interventricular
sulcus

17. Figure 21.7b Sectional Anatomy of the Heart, Part I
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Brachiocephalic
Superior
vena cava
Right
pulmonary
arteries
Ascending
aorta
Fossa ovalis
Opening of
coronary sinus
RIGHT ATRIUM
Pectinate muscles
Conus arteriosus
Cusp of right AV
(tricuspid) valve
Chordae tendineae
Papillary muscle
RIGHT VENTRICLE
Inferior vena cava
trunk
Aortic arch
LEFT
ATRIUM
Left common carotid artery
Left subclavian artery
Ligamentum arteriosum
Pulmonary trunk
Pulmonary valve
Left pulmonary
arteries
Left pulmonary
veins
Interatrial septum
Aortic valve
Cusp of left AV
(mitral) valve
LEFT VENTRICLE
Interventricular
septum
Trabeculae
carneae
Moderator
band
Descending
aorta
Diagrammatic frontal section through the relaxed heart shows the major
landmarks and the path of blood flow through the atria and ventricles (arrows).

18. Cardiac cycle
 All of the electrical and mechanical events that take place
during one heart beat are referred to as one cardiac cycle.
 Systole — contraction
 Atrial systole
 Ventricular systole
 Blood is pushed out of the heart.
 AV valves are closed
 Diastole — relaxation, when the chambers of the heart fill.
 Atrial diastole
 RA receives blood from SVC and IVC.
 LA receives blood from pulmonary veins.
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19. Figure 21.9a Valves of the Heart
Transverse Sections, Superior View, Atria and Vessels Removed Frontal Sections Through Left Atrium and Ventricle
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POSTERIOR
ANTERIOR
RIGHT
VENTRICLE
LEFT
VENTRICLE
Fibrous
skeleton
Left AV (bicuspid)
valve (open)
Aortic valve
(closed)
Pulmonary
valve (closed)
Right AV
(tricuspid)
valve (open)
Ventricular Diastole
Aortic valve
(closed)
When the ventricles are relaxed, the AV valves are open and
the semilunar valves are closed. The chordae tendineae are
loose, and the papillary muscles are relaxed.
Pulmonary
veins
LEFT
ATRIUM
Left AV
(bicuspid)
valve (open)
Chordae
tendineae
(loose)
Papillary
muscles
(relaxed)
LEFT VENTRICLE
(dilated)
Aortic valve closed

20. Figure 21.9b Valves of the Heart
Ventricular Systole
Transverse Sections, Superior View, Atria and Vessels Removed Frontal Sections Through Left Atrium and Ventricle
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When the ventricles are contracting, the AV valves
are closed and the semilunar valves are open. In
the frontal section notice the attachment of the left
AV valve to the chordae tendineae and papillary
muscles.
RIGHT
VENTRICLE
Right AV
(tricuspid) valve
(closed)
Fibrous
skeleton
Left AV
(bicuspid) valve
(closed)
LEFT
VENTRICLE
Aortic valve
(open)
Pulmonary
valve (open)
Aortic valve open
LEFT
ATRIUM
Aorta
Aortic sinus
Aortic valve
(open)
Left AV
(bicuspid)
valve (closed)
Chordae
tendineae
(tense)
Papillary
muscles
(contracted)
Left ventricle
(contracted)

21. Blood supply to the heart
• The heart muscle is receiving its own
blood from right and left coronary arteries.
• Coronary arteries are originating from the
base of the ascending aorta.
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22. Figure 21.10a Coronary Circulation
Left common carotid
artery
Brachiocephalic
trunk
Pulmonary
Small cardiac
vein
Anterior cardiac
veins
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Coronary vessels supplying the
anterior surface of the heart
Marginal branch
of RCA
Atrial
branches
of RCA
LEFT
RIGHT VENTRICLE
VENTRICLE
RIGHT
ATRIUM
Aortic
arch
Right
coronary
artery
(RCA)
trunk
Left subclavian artery
LEFT ATRIUM
Left coronary
artery (LCA)
Circumflex
branch of LCA
Diagonal branch
of LCA
Anterior
interventricular
branch of LCA
Great cardiac
vein

23. Figure 21.10b Coronary Circulation
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LEFT
ATRIUM
Coronary vessels supplying the
posterior surface of the heart
Marginal
branch of LCA
Posterior vein
of left ventricle
Posterior
left ventricular
branch of LCA
Circumflex
branch of LCA
Atrial branch
of LCA
LEFT
VENTRICLE
RIGHT
VENTRICLE
RIGHT
ATRIUM
Coronary
sinus
Small cardiac
vein
Right
coronary
artery (RCA)
Right marginal
branch of RCA
Middle cardiac
vein
Posterior interventricular
branch of RCA
Great cardiac vein

24. The Cardiac Cycle
• The cardiac cycle consists of alternate
periods of contraction and relaxation
• Contraction is systole
• Blood is ejected into the ventricles
• Blood is ejected into the pulmonary trunk and the
ascending aorta
• Relaxation is diastole
• Chambers are filling with blood
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25. Figure 21.11 The Cardiac Cycle
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Cardiac
cycle
100
msec
370
msec
0
800 msec
msec
Ventricular diastole—early:
As ventricles relax, pressure in ventricles
drops; blood flows back against cusps of
semilunar valves and forces them closed.
Blood flows into the relaxed atria.
Atrial systole ends,
atrial diastole
begins
Ventricular systole—
second phase: As
ventricular pressure rises
and exceeds pressure
in the arteries, the
semilunar valves
open and blood
is ejected.
Ventricular
diastole—late:
All chambers are relaxed.
Ventricles fill passively.
Ventricular systole—
first phase:
Ventricular contraction
pushes AV valves
closed but does not
create enough
pressure to open
semilunar valves.
Atrial systole begins:
Atrial contraction forces a small amount
of additional blood into relaxed ventricles.
Start
Atrial sy stole
Atrial diastole
Ventricular diastole
Ventricular systole

26. Figure 21.12a The Conducting System of the Heart
Sinoatrial
(SA) node
Internodal
pathways
Atrioventricular
(AV) node
Left bundle branch
Right bundle branch
Moderator band Purkinje fibers
The stimulus for contraction is generated by pacemaker cells at
the SA node. From there, impulses follow three different paths
through the atrial walls to reach the AV node. After a brief delay,
the impulses are conducted to the bundle of His (AV bundle), and
then on to the bundle branches, the Purkinje fibers, and the
ventricular myocardial cells.
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AV bundle

27. Figure 21.12b The Conducting System of the Heart
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SA node activity and
atrial activation begin.
SA node
Time = 0
Stimulus spreads across
the atrial surfaces and
reaches the AV node. AV node
Elapsed time = 50 msec
There is a 100 msec delay
at the AV node. Atrial
contraction begins.
Elapsed time = 150 msec
AV
bundle
Bundle
branches
The impulse travels along the
interventricular septum within
the AV bundle and the bundle
branches to the Purkinje fibers
and, via the moderator band,
to the papillary muscles of the
right ventricle.
Moderator
Elapsed time = 175 msec band
The impulse is distributed by
Purkinje fibers and relayed
throughout the ventricular
myocardium. Atrial contraction
is completed, and ventricular
contraction begins.
Elapsed time = 225 msec
Purkinje
fibers
The movement of the contractile stimulus through the
heart is shown in STEPS 1–5.

28. The Cardiac Cycle
 The ECG is a recording of the electrical
events in the heart and reveals the
condition of cunducting system of the heart.
 P wave — atrial depolarization
 QRS complex — ventricular depolarization
 T wave — ventricular repolarization
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29. © 2012 Pearson Education, Inc.
ECG

30. Figure 21.13 The Autonomic Innervation of the Heart
Vagal nucleus
Medulla
oblongata
Vagus (N X)
Cardioinhibitory
center
Sympathetic Parasympathetic
Sympathetic
preganglionic
Sympathetic ganglia
(cervical ganglia and
superior thoracic
ganglia [T1–T4])
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Parasympathetic
preganglionic
fiber
Synapses in
cardiac plexus
Parasympathetic
postganglionic
fibers
fiber
Sympathetic
postganglionic fiber
Cardiac nerve
Spinal cord
Cardioacceleratory
center