Chapter 22
*Lecture Outline
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Chapter 22 Outline
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Overview of the Cardiovascular System
Anatomy of the Heart
Coronary Circulation
How the Heart Beats: Electrical Properties
of Cardiac Tissue
Innervation of the Heart
Tying It All Together: The Cardiac Cycle
Aging and the Heart
Development of the Heart
Overview of the
Cardiovascular System
• The heart propels blood to and from most
body tissues via two basic types of blood
vessels called arteries and veins.
• Arteries are defined as blood vessels that
carry blood away from the heart.
• Veins are defined as blood vessels that
carry blood back to the heart.
• The arteries and veins entering and
leaving the heart are called great vessels.
General Characteristics and
Functions of the Heart
• Blood flow through the heart is
unidirectional because of four valves
within the heart.
• The heart is functionally two side-by-side
pumps that work at the same rate and
pump the same volume of blood.
– One pump directs blood to the lungs.
– One pump directs blood to most body tissues.
General Characteristics and
Functions of the Heart
• The heart generates blood pressure
through alternate cycles of the heart wall’s
contraction and relaxation.
• Blood pressure is the force of the blood
pushing against the inside walls of blood
vessels.
• A minimum blood pressure is essential to
circulate blood throughout the body.
Pulmonary and Systemic
Circulations
The cardiovascular system consists of two
circulations:
1. Pulmonary—right side of the heart and the
pulmonary arteries and veins; conveys blood to
the lungs and back to the left side of the heart
2. Systemic—left side of the heart and arteries
and veins; conveys blood to most body tissues
and back to the right side of the heart
Cardiovascular System
Figure 22.1
Position of the Heart
• Slightly left of midline deep to the sternum
in a compartment of the thorax known as
the mediastinum
Figure 22.2
Position of the Heart
• During development, the heart rotates
such that the right side or right border
(primarily formed by the right atrium and
ventricle) is located more anteriorly.
• The left side or left border (primarily
formed by the left atrium and ventricle) is
located more posteriorly.
Position of the Heart
• The posterosuperior surface of the heart is
mainly the left atrium and is called the
base of the heart.
• The superior border is formed by the
great arterial vessels and the superior
vena cava.
• The inferior conical end is called the apex.
• The inferior border is formed by the right
ventricle.
Position of the Heart
Figure 22.2
Pericardium
• The heart is enclosed within a tough sac
called the pericardium
• Restricts heart
movements so
that it moves only
slightly within the
thorax
Figure 22.2
Pericardium
Composed of two parts:
1. Fibrous pericardium—outer covering of
tough, dense connective tissue
2. Serous pericardium—composed of two
layers:
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parietal layer—lines the inner surface of the
fibrous pericardium
visceral layer (epicardium)—covers the outer
surface of the heart
– the small space between the parietal and visceral layers is
called the pericardial cavity
Pericardium
Figure 22.3
Anatomy of the Heart Wall
The heart wall consists of three distinctive layers
(from superficial to deep):
1. Epicardium—consists of the visceral layer of
the serous pericardium and areolar connective
tissue
2. Myocardium—cardiac muscle; thickest of the
three layers
3. Endocardium—internal surface of the heart
chambers and external surface of the heart
valves
Anatomy of the Heart Wall
Figure 22.4
External Heart Anatomy
• Composed of four hollow chambers: two smaller and
superior atria (sing., atrium) and two larger inferior
ventricles
• The anteroinferior borders of the atria form a muscular
extension called the auricle
• The atria and ventricles are separated from each other
by a relatively deep groove called the coronary sulcus
• The anterior interventricular sulcus and posterior
interventricular sulcus are located between the right
and left ventricles and run from the coronary sulcus
toward the apex of the heart
External Heart Anatomy
Figure 22.5
External Heart Anatomy
Figure 22.5
Internal Heart Anatomy:
Chambers and Valves
The heart possesses four chambers:
1. Right atrium
2. Right ventricle
3. Left atrium
4. Left ventricle
The heart also possesses four valves:
1. Right atrioventricular (tricuspid)
2. Pulmonary semilunar
3. Left atrioventricular (bicuspid or mitral)
4. Aortic semilunar
Right Atrium
Receives venous blood from heart, the muscles,
and systemic circulation; three veins drain into the
right atrium:
1. Superior vena cava
2. Inferior vena cava
3. Coronary sinus
Separating the right atrium from the right ventricle
is the right atrioventricular valve (tricuspid valve)
Right Atrium
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Aortic arch
Ligamentum arteriosum
Ascending aorta
Left pulmonary artery
Superior vena cava
Pulmonary trunk
Right pulmonary artery
Left pulmonary veins
Right pulmonary veins
Left atrium
Right auricle
Fossa ovalis
Interatrial septum
Opening for coronary sinus
Right atrium
Opening for inferior
vena cava
Right atrioventricular valve
Aortic semilunar valve
Left atrioventricular valve
Pulmonary semilunar
valve
Trabeculae carneae
Interventricular septum
Chordae tendineae
Left ventricle
Papillary muscle
Septomarginal trabecula
Right ventricle
Inferior vena cava
Descending aorta
Aortic arch
Ligamentum arteriosum
Ascending aorta
Superior vena cava
Pulmonary trunk
Right auricle
Right atrium
Fossa ovalis
Interatrial septum
Pectinate muscle
Opening for inferior
vena cava
Pulmonary semilunar valve
Right coronary artery
Interventricular septum
Right atrioventricular valve
Left ventricle
Chordae tendineae
Figure 22.6
Trabeculae carneae
Papillary muscle
Right ventricle
Coronal section, anterior view
© The McGraw- Hill Companies, Inc./Photo and Dissection by Christine Eckel
Right Atrium
• Deoxygenated venous blood flows from
the right atrium to the right ventricle
through the right atrioventricular valve.
• The right atrioventricular valve is forced
closed when the right ventricle begins to
contract, preventing blood backflow into
the right atrium.
Right Ventricle
• Receives deoxygenated venous blood
from the right atrium
• An interventricular septum forms a thick
wall between the right and left ventricles
• The inner wall of each ventricle displays
large, irregular muscular ridges called
trabeculae carneae
Right Ventricle
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Aortic arch
Ligamentum arteriosum
Ascending aorta
Left pulmonary artery
Superior vena cava
Pulmonary trunk
Right pulmonary artery
Left pulmonary veins
Right pulmonary veins
Left atrium
Right auricle
Fossa ovalis
Aortic semilunar valve
Interatrial septum
Opening for coronary sinus
Right atrium
Opening for inferior
vena cava
Right atrioventricular valve
Left atrioventricular valve
Pulmonary semilunar
valve
Trabeculae carneae
Interventricular septum
Chordae tendineae
Left ventricle
Papillary muscle
Septomarginal trabecula
Right ventricle
Inferior vena cava
Descending aorta
Aortic arch
Ligamentum arteriosum
Ascending aorta
Superior vena cava
Pulmonary trunk
Right auricle
Right atrium
Fossa ovalis
Interatrial septum
Figure 22.6
Pectinate muscle
Opening for inferior
vena cava
Pulmonary semilunar valve
Right coronary artery
Interventricular septum
Right atrioventricular valve
Left ventricle
Chordae tendineae
Trabeculae carneae
Papillary muscle
Right ventricle
Coronal section, anterior view
© The McGraw- Hill Companies, Inc./Photo and Dissection by Christine Eckel
Right Ventricle
• There are typically three cone-shaped muscle
projections inside the right ventricle called papillary
muscles.
• The papillary muscles anchor thin strands of strong
connective tissue made up of collagen fibers called
chordae tendineae.
• The chordae tendineae attach to three cusps of the
(tricuspid) right atrioventricular valve.
• Cusps are triangular flaps that hang down into the
ventricle.
• The chordae tendineae prevent the cusps from
prolapsing into the right atrium when the right ventricle
contracts.
Right Ventricle
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Aortic arch
Ligamentum arteriosum
Ascending aorta
Left pulmonary artery
Superior vena cava
Pulmonary trunk
Right pulmonary artery
Left pulmonary veins
Right pulmonary veins
Left atrium
Right auricle
Fossa ovalis
Aortic semilunar valve
Interatrial septum
Opening for coronary sinus
Right atrium
Opening for inferior
vena cava
Right atrioventricular valve
Left atrioventricular valve
Pulmonary semilunar
valve
Trabeculae carneae
Interventricular septum
Chordae tendineae
Left ventricle
Papillary muscle
Septomarginal trabecula
Right ventricle
Inferior vena cava
Descending aorta
Aortic arch
Ligamentum arteriosum
Ascending aorta
Superior vena cava
Pulmonary trunk
Right auricle
Right atrium
Fossa ovalis
Interatrial septum
Figure 22.6
Pectinate muscle
Opening for inferior
vena cava
Pulmonary semilunar valve
Right coronary artery
Interventricular septum
Right atrioventricular valve
Left ventricle
Chordae tendineae
Trabeculae carneae
Papillary muscle
Right ventricle
Coronal section, anterior view
© The McGraw- Hill Companies, Inc./Photo and Dissection by Christine Eckel
Right Ventricle
• At the superior end or roof of the ventricle
is a smooth area called the conus
arteriosus.
• Beyond the conus arteriosus is the
pulmonary semilunar valve, which
marks the end of the ventricle and the
beginning of the pulmonary trunk.
Semilunar Valves
• Two of them: pulmonary and aortic
• Located in the roof of right and left ventricles,
respectively
• Each valve is composed of three thin, halfmoon-shaped, pocketlike semilunar cusps
• When ventricles contract, blood pushes cusps
against the arterial trunks
• When ventricles relax, some blood flows back
toward the ventricles, enters the pockets of the
cusps and forces them toward midline, thus
closing the valve
Valves of the Heart
Figure 22.7
Left Atrium
• Oxygenated blood from the lungs travels
through the pulmonary veins to the left atrium.
• The left atrium is separated from the left
ventricle by the left atrioventricular valve,
which is also referred to as the bicuspid or mitral
valve.
• This valve only has two triangular cusps.
• This valve is forced shut when the left ventricle
contracts in a similar fashion to the closing of the
right atrioventricular valve.
Left Ventricle
• The wall is typically
three times thicker
than the right
ventricular wall.
Figure 22.8
Left Ventricle
• The left ventricle has to pump blood to the
entire body, except for the lungs, and
therefore has to generate a greater blood
pressure.
• At the superior end or roof of the left
ventricle is the aortic semilunar valve,
which marks the end of the left ventricle
and the beginning of the aorta.
Valves of the Heart
Valves of the Heart
Coronary Circulation
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The right and left coronary arteries
travel within the coronary sulcus and
supply the heart wall muscle with oxygen
and nutrients.
The coronary arteries are the only
branches given off by the ascending
aorta just superior to the aortic semilunar
valve.
Coronary Arteries
Figure 22.9
Right Coronary Artery
Branches into two arteries:
1. Marginal artery—supplies the right
border of the heart
2. Posterior interventricular artery—
supplies the posterior surface of the left
and right ventricles
Left Coronary Artery
Branches into two arteries:
1. Anterior interventricular artery—also
called the left anterior descending artery,
supplies the anterior surface of both
ventricles and most of the interventricular
septum
2. Circumflex artery—supplies the left
atrium and ventricle
Coronary Veins
Venous return of blood from the heart wall muscle
occurs through three major veins:
1. Great cardiac vein—runs alongside the
anterior interventricular artery
2. Middle cardiac vein—runs alongside the
posterior interventricular artery
3. Small cardiac vein—travels close to the
marginal artery
All three of the above veins drain into a large vein
called the coronary sinus that drains into the right
atrium.
Coronary Veins
Figure 22.9
Conducting System of the Heart
• The myocardium is composed of cardiac muscle
fibers.
• Cardiac muscle fibers contract as a single unit
because they are all connected with low
resistance cell-to-cell junctions called gap
junctions.
• Gap junctions comprise the intercalated discs
shared by adjacent cardiac muscle fibers.
• Therefore, an electrical impulse is distributed
immediately and spontaneously throughout the
myocardium.
Comparison of Cardiac
and Skeletal Muscle
Structure of Cardiac Muscle
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Intercalated disc
Openings of
transverse tubules
Intercalated disc
Desmosome
Gap junction
Cardiac muscle cell
Sarcolemma
Nucleus
Mitochondrion
(a) Cross section of cardiac muscle cell
Sarcomere
Intercalated discs
Striations
Sarcolemma
Transverse
tubule
Sarcoplasmic
reticulum
Nucleus
Mitochondrion
Myofibrils
LM 1000x
Z disc
I band
H zone
M line
Z disc
(c) Longitudinal section of cardiac muscle
I band
A band
(b) Cardiac muscle cell, longitudinal view
Figure 22.10
c © Dennis Drenner/Visuals Unlimited
Conducting System of the Heart
• The heart exhibits autorhythmicity, which
means it is capable of initiating its own heartbeat
independent of external nerves.
• The electrical impulse that initiates the heartbeat
comes from specialized cardiac muscle cells
called the sinoatrial (SA) node or the
pacemaker.
• The SA node is located on the posterior wall of
the right atrium adjacent to the opening of the
superior vena cava.
• The SA node generates 70–80 impulses per
minute under parasympathetic control.
Conducting System of the Heart
• Impulses from the SA node travel to the left
atrium and the atrioventricular (AV) node
located in the floor of the right atrium.
• Electrical activity then leaves the AV node into
the atrioventricular (AV) bundle (bundle of
His), which extends into the interventricular
septum.
• Once within the septum, the AV bundle divides
into left and right bundles.
Conducting System of the Heart
• These bundles pass the impulse to
conduction cells called Purkinje fibers
that begin at the apex of the heart.
• The Purkinje fibers spread the impulse
superiorly from the apex to all of the
ventricular myocardium.
Conducting System of the Heart
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Superior vena cava
Right atrium
Left atrium
Sinoatrial node (pacemaker)
Internodal pathway
Atrioventricular node
Atrioventricular bundle
(bundle of His)
Interventricular
septum
Right bundle
Purkinje fibers
Purkinje fibers
Left bundles
Internodal
pathway
Atrioventricular
node
Atrioventricular
bundle
1 Muscle impulse is generated at the sinoatrial node. It spreads throughout the atria and
to the atrioventricular node by the internodal pathway.
2 Atrioventricular node cells delay the
muscle impulse as it passes to the
atrioventricular bundle.
Atrioventricular
bundle
Interventricular
septum
3 The atrioventricular bundle (bundle
of His) conducts the muscle impulse
into the interventricular septum.
Figure 22.11
Left and right
bundle branches
4 Within the interventricular septum, the
right and left bundles split from the
atrioventricular bundle.
Purkinje fibers
5 The muscle impulse is delivered to Purkinje
fibers in each ventricle and distributed
throughout the ventricular myocardium.
Innervation of the Heart
• The heart, like most other organs, is
innervated by both the sympathetic and
parasympathetic divisions of the
autonomic nervous system.
• The anatomical components of both
divisions make up the coronary plexus.
• Autonomic innervation does not initiate a
heartbeat, but it can increase or decrease
the rate of the heartbeat.
Innervation of the Heart
Figure 22.12
Sympathetic Innervation
• Starts with neurons located in T1–T5
segments of the spinal cord
• Preganglionic axons enter the sympathetic
trunk and synapse on ganglionic neurons.
• Postganglionic axons project from all three
cervical ganglia and travel to the heart via
cardiac nerves.
• Sympathetic input to the heart increases
the rate and force of heart contractions.
Parasympathetic Innervation
• Starts with neurons in the medulla
oblongata via the left and right vagus
nerves (CN X)
• Decreases heart rate but generally has no
effect on force of contraction
Coordinated Sequence of Heart
Chamber Contractions
1. SA node generates an impulse.
2. Both atria contract almost simultaneously
(systole) while ventricles are relaxing
(diastole).
3. Impulse goes to AV node and then to the
ventricles.
4. Ventricles contract (systole) while atria
relax (diastole).
Ventricular Systole and Diastole
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(a) Ventricular Systole (Contraction)
Aortic arch
Blood flow into
ascending aorta
Ascending
aorta
Pulmonary
trunk
Blood flow into
right atrium
Blood flow into
pulmonary trunk
Right
atrium
Left
atrium
Ventricular contraction pushes
blood against the open AV
valves, causing them to close.
Contracting papillary muscles
and the chordae tendineae
prevent valve flaps from
everting into atria.
Ventricles contract, forcing
semilunar valves to open and
blood to enter the pulmonary
trunk and the ascending aorta.
Atrioventricular valves closed
Semilunar valves open
Right ventricle
Left ventricle
Cusp of
semilunar
valve
Cusp of
atrioventricular
valve
Blood in
ventricle
Posterior
Left AV
valve (closed)
Right AV
valve (closed)
Left ventricle
Right
ventricle
Aortic semilunar
valve (open)
Pulmonary
semilunar
valve (open)
Figure 22.13
Anterior
Transverse section
Ventricular Systole and Diastole
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(b) Ventricular Diastole (Relaxation)
Aortic arch
Blood flow into
right atrium
Blood flow into
left ventricle
Right
atrium
Left
atrium
During ventricular relaxation,
some blood in the ascending
aorta and pulmonary trunk
flows back toward the
ventricles, filling the semilunar
valve cusps and forcing them
to close.
Blood flow into
right ventricle
Ventricles relax and fill with
blood both passively and
then by atrial contraction as
AV valves remain open.
Semilunar valves closed
Atrioventricular valves open
Atrium
Right ventricle
Cusp of
atrioventricular
valve
Left ventricle
Blood
Cusps of
semilunar
valve
Chordae
tendineae
Papillary
muscle
Posterior
Left AV
valve (open)
Right AV
valve (open)
Left ventricle
Right ventricle
Aortic semilunar
valve (closed)
Pulmonary
semilunar
valve (closed)
Figure 22.13
Anterior
Transverse section
Cardiac Cycle
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Atria contract
Atria relax
Atria relax
Semilunar
valves
open
AV
valves
open
All
valves
closed
Ventricles contract
Ventricles relax
1
AV
valves
closed
Atrial systole
Atria contract; AV valves are open,
semilunar valves are closed
Phase
Early
ventricular
systole
Atrial
systole
Structure
Atria
Ventricles contract
Early ventricular systole
Atria relax; ventricles begin to contract;
AV valves are forced closed (lubb
sound); semilunar valves still closed
2
Late
ventricular
systole
3
Early
ventricular
diastole
Late
ventricular
diastole
Contract
Relax
Relax
V entricles
Relax
Contract
Relax
A V valves
Open
Semilunar
valves
Time
(seconds)
Closed
Closed
0.0
Open
Open
0.1
0.2
Late ventricular systole
Atria continue to relax; ventricles contract;
AV valves remain closed; semilunar
valves are forced open
Closed
0.3
0.4
0.5
Atria relax
0.6
0.7
Atria relax
Semilunar
valves closed
AV
valves
open
All
valves
closed
Ventricles relax
5
Figure 22.14
Late ventricular diastole
Atria and ventricles relax; atria continue
passively filling with blood; AV valves
open and ventricles begin to passively fill;
semilunar valves remain closed
Ventricles relax
4
Early ventricular diastole
Atria and ventricles relax; AV valves
remain closed and semilunar valves close
(dupp sound); atria continue passively
filling with blood
0.8
Blood Flow Through the Heart
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Blood Flow Through the Heart
Table 22.3
Systemic veins
Superior
and inferior
venae cavae
Right
atrium
Right
atrioventricular
valve
Right
ventricle
Pulmonary
semilunar
valve
Gas and nutrient
exchange
in peripheral
tissues
Systemic
arteries
Chamber of the Heart
Pulmonary
trunk and
arteries
Gas exchange
in the lungs
Aorta
Aortic
semilunar
valve
Receives Blood From
Left
ventricle
Left
atrioventricular
valve
Sends Blood To
Left
atrium
Pulmonary
veins
Valves Through Which Blood
Flows
Right AV valve
Right atrium
Superior vena cava, inferior vena Right ventricle
cava, coronary sinus
Right ventricle
Right atrium
Pulmonary trunk (blood enters
Pulmonary semilunar valve
vessels of pulmonary circulation)
Left atrium
Pulmonary veins
Left ventricle
Left AV valve
Left ventricle
Left atrium
Ascending aorta (blood enters
vessels of systemic circulation)
Aortic semilunar valve
Development of the Heart
Figure 22.15
Development of the Heart
Figure 22.16
Development of the Heart