PowerLecture:
Chapter 9
Circulation - The Heart
and Blood Vessels
Learning Objectives




List the basic components of the human
circulatory system.
Trace the routes of blood flow in the human
cardiovascular system.
Explain the factors that cause blood to exist
under different pressures.
Describe the major cardiovascular disorders
and their causes.
Impacts/Issues
The Breath of Life
The Breath of Life
During sudden cardiac arrest the
heart stops its regular beating.
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

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CPR (cardiopulmonary resuscitation)
is an immediate life-saving technique.
As soon as possible a defibrillator
should be used to shock the heart
back to its usual rhythm; AEDs
(automated external defibrillators) are
now available in many public places.
The heart, and its associated blood
vessels, is a complicated lifesustaining system.
How Would You Vote?
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 Would
you favor mandatory CPR training in
high schools?


a. Yes, it would save countless lives.
b. No, it’s just another graduation requirement.
Section 1
The Cardiovascular
System – Moving Blood
Through the Body
The Cardiovascular System – Moving
Blood Through the Body
The heart and blood vessels make up the
cardiovascular system.


The cardiovascular system has two major
elements:
•
•

The heart is the muscular pump that generates the
pressure required to move the blood through the
body.
Blood vessels are the distribution tubes of varying
diameters.
The route of circulation: heart >>> arteries >>>
arterioles >>> capillaries >>> venules >>> veins
and finally back to the heart.
carotid arteries
jugular veins
ascending aorta
superior vena cava
pulmonary arteries
pulmonary veins
heart
coronary arteries
hepatic portal vein
brachial artery
renal vein
renal artery
inferior vena cava
abdominal aorta
iliac veins
iliac arteries
femoral vein
femoral artery
Fig. 9.1, p.158
The Cardiovascular System – Moving
Blood Through the Body
Circulating blood is vital to maintain
homeostasis.



The cardiovascular system is the body’s internal
rapid-transport system for oxygen, nutrients,
secretions, and wastes via the blood.
Homeostasis depends on the reliable supply of
blood to all of the body.
food, water intake
oxygen intake
DIGESTIVE
SYSTEM
nutrients,
water,
salts
RESPIRATORY
SYSTEM
oxygen
carbon
dioxide
CIRCULATORY
SYSTEM
elimination
of food
residues
elimination
of carbon
dioxide
URINARY
SYSTEM
water,
solutes
rapid transport
to and from all
living cells
elimination of
excess water,
salts, wastes
Fig. 9.2, p.159
The Cardiovascular System – Moving
Blood Through the Body
The cardiovascular system is linked to the
lymphatic system.



Because of the pressure in the cardiovascular
system, water and proteins leak out to become
part of the interstitial fluid.
The lymphatic system vessels pick up the fluid
and return it to the general circulation.
Section 2
The Heart: A Double
Pump
The Heart: A Double Pump
The heart is a durable pump made mostly
of cardiac muscle (myocardium).



The heart is surrounded by a tough, fibrous sac
(pericardium).
The inner lining of the heart is the
endocardium; it is composed of connective
tissue and epithelial cells (endothelium).
right lung
left lung
1
2
3
4
5
6
7
8
diaphragm
heart
rib cage
Fig. 9.3a, p.160
The Heart: A Double Pump
The heart has two halves and four
chambers.


The septum divides the heart into two halves,
right and left.
•
•
•

Each half consists of an atrium (receiving chamber)
and a ventricle (pumping chamber) separated by an
atrioventricular valve (AV valve).
The AV valve on the right is a tricuspid valve; the
one on the left is the bicuspid, or mitral valve.
Chordae tendineae (“heartstrings”) connect the AV
valve flaps to the ventricle wall.
Blood exits each ventricle through a semilunar
valve.
front of chest
three
cusps
right atrioventricular
valve (tricuspid)
right semilunar
valve (between
right ventricle
and pulmonary
arteries)
two
cusps
left
atrioventricular
valve (bicuspid
or mitral valve)
left semilunar
valve (between
left ventricle
and aorta)
Fig. 9.3c, p.160
The Heart: A Double Pump

Heart muscle cells are serviced by the coronary
circulation; coronary arteries branch off the
aorta, forming a capillary bed around the heart.
coronary
artery
Figure 9.4b
aorta
(superior
vena cava)
(left pulmonary artery)
(left pulmonary veins)
cardiac vein
left coronary artery
right
coronary
artery
cardiac vein
(inferior vena cava)
© 2007 Thomson Higher Education
Fig. 9.4a, p.161
aorta
superior vena cava
trunk of
pulmonary
arteries
right semilunar valve
left semilunar
valve
right pulmonary veins
left pulmonary
veins
right atrium
left atrium
left AV valve
(opened)
right AV valve
(opened)
left ventricle
right ventricle
muscles that keep valve
from pointing wrong way
inferior vena cava
endothelium,
connective
tissue
pericardium
septum (partition that divides
the heart into two halves)
© 2007 Thomson Higher Education
myocardium
Fig. 9.3b, p.160
The Heart: A Double Pump
In a “heartbeat,” the heart’s chambers
contract, then relax.


The cardiac cycle is a sequence of contraction
(systole) and relaxation (diastole).
•
•
•
As the atria fill, the ventricles are relaxed.
Pressure of the blood in the atria forces the AV
valves open; the ventricles fill as the atria contract.
When the ventricles contract, the AV valves close,
and blood flows out through the semilunar valves.
The Heart: A Double Pump


The cardiac output is the amount of blood
each ventricle can pump in a minute; on
average the output from each ventricle is about
5 liters.
The heart sound “lub” is made by the closing of
the AV valves; the “dup” sound is the closure of
the semilunar valves.
4 Fluid pressure in
filling atria
opens AV valves;
blood flows into
ventricles
1 Atria, contract,
and fluid pressure
in ventricles rises
sharply.
Heart
sounds
3 Ventricles
relax even
as the atria
begin to
fill and start
another cycle.
2 Ventricles contract;
blood is pumped
into the pulmonary
artery and the
aorta
Fig. 9.5, p.161
4 Fluid pressure in
filling atria
opens AV valves;
blood flows into
ventricles
1 Atria, contract,
and fluid pressure
in ventricles rises
sharply.
Heart
sounds
3 Ventricles
relax even
as the atria
begin to
fill and start
another cycle.
2 Ventricles contract;
blood is pumped
into the pulmonary
artery and the
aorta
Stepped Art
Fig. 9.5, p.161
Section 3
The Two Circuits of
Blood Flow
The Two Circuits of Blood Flow
The pulmonary circuit: Blood picks up
oxygen in the lungs.



The pulmonary circuit receives blood from the
tissues, taking it through the lungs for gas
exchange.
The path of blood flow: blood from tissues
enters the right atrium >>> tricuspid valve >>>
right ventricle >>>right semilunar valve >>>
pulmonary arteries >>> lungs >>> pulmonary
veins >>> left atrium.
The Two Circuits of Blood Flow

Blood returning from the body tissues is high in
carbon dioxide and low in oxygen; these
concentrations are reversed after passage
through the lung capillaries.
right pulmonary artery
left pulmonary artery
capillary bed
of left lung
capillary bed
of right lung
pulmonary
trunk
(from
systemic
circuit)
(to systemic circuit)
pulmonary
veins
heart
© 2007 Thomson Higher Education
Fig. 9.6a, p.162
The Two Circuits of Blood Flow
In the systemic circuit, blood travels to and
from tissues.
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
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
In the systemic circuit, oxygenated blood is
pumped through the body.
Blood moves from the left atrium >>> bicuspid
valve >>> left ventricle >>>left semilunar valve
>>> aorta >>> body tissues.
Blood from the upper body travels through the
superior vena cava; blood from the lower body
travels through the inferior vena cava.
The Two Circuits of Blood Flow
Blood from the digestive tract is shunted
through the liver for processing.
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

After a meal, blood laden with nutrients is
carried from the digestive tract in the hepatic
portal vein to the liver capillaries.
There it passes through the liver capillary beds
before leaving via the hepatic vein to return to
the general circulation; oxygenated blood
reaches the liver through the hepatic artery.
Systemic
circuit for
blood flow
capillary beds of head
and upper extremities
(to pulmonary
circuit)
aorta
(from
pulmonary
circuit)
heart
capillary beds of other
organs in thoracic cavity
diaphragm (muscular
partition between thoracic
and abdominal cavities)
capillary bed
of liver
capillary bed of intestines
capillary beds of other
abdominal organs and
lower extremities
© 2007 Thomson Higher Education
Fig. 9.6b, p.162
lungs
100%
heart’s right half
digestive tract
liver
kidneys
skeletal muscle
brain
skin
bone
cardiac muscle
all other regions
© 2007 Thomson Higher Education
heart’s left half
21%
6%
20%
15%
13%
9%
5%
3%
8%
Fig. 9.6c, p.162
Fig. 9.6c(2), p.162
Section 4
How Cardiac Muscle
Contracts
How Cardiac Muscles Contract
Electrical signals from “pacemaker” cells
drive the heart’s contractions.
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
Cardiac muscle cells are linked by intercalated
discs, which rapidly pass signals to contract
throughout the heart.
•
•
The cardiac conduction system consists of
noncontractile cells that are self-excitatory
(pacemaker cells).
Excitation for a heartbeat is initiated in the sinoatrial
(SA) node; it then passes to the atrioventricular
(AV) node and on to the Purkinje fibers, which
make contact with the muscle cells that result in
ventricular contraction.
junction
between
adjacent
cells
intercalated disc
Fig. 9.7, p.164
SA node
AV node
bundle of
connecting
muscle fibers
Purkinje fibers
contractile heart
muscle cells
Fig. 9.8a, p.164
How Cardiac Muscles Contract

It is the action of the cardiac pacemaker (SA
node) that produces our normal heartbeat.
The nervous system adjusts heart activity.
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

The nervous system can adjust the rate and
strength of cardiac muscle contraction;
stimulation by one set of nerves increases the
rate and strength while stimulation by other
nerves decreases heart rate.
Centers for nervous control of the heart lie in
the spinal cord and the brain.
Section 5
Blood Pressure
Blood Pressure
Blood exerts pressure against the walls of
blood vessels.
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

The force of blood against
the vessel walls can be
measured as blood pressure.
Normal systolic pressure
(peak pressure in the aorta)
is 120 mm of Hg; normal diastolic pressure
(lowest pressure in the aorta) is 80 mm.
Figure 9.9
Blood Pressure
 Blood
pressure values give important clues
as to the condition of the vessels and the flow
of blood through them.


In hypertension, the blood pressure is too high,
which can lead to stroke or heart attack.
In hypotension, the blood pressure is too low;
loss of water or blood volume can lead to
circulatory shock.
Fig. 9.10, p.165
Table 9.1, p.165
Section 6
Structure and Functions
of Blood Vessels
Structure and Functions of Blood Vessels
Arteries are large blood pipelines.
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

Because of their elastic walls,
arteries tend to “smooth out” the
pressure changes associated with
the discontinuous pumping cycle of
the heart (felt as a pulse).
Because of their large diameters, arteries
present little resistance to flow; blood pressure
does not decrease very much in them.
Artery
connective
tissue coat
smooth
muscle
endothelium
elastic tissue
elastic tissue
Fig. 9.11a, p.166
Structure and Functions of Blood Vessels
Arterioles are control points for blood flow.
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
Arteries branch into smaller arterioles, where
the greatest pressure drop occurs.
The wall of an arteriole has rings of smooth
muscle over a single layer of elastic fibers.
Arterioles serve as control points where
adjustments can be made in blood volume
distribution.
Arteriole
smooth muscle rings
over elastic tissue
endothelium
Fig. 9.11b, p.166
Structure and Functions of Blood Vessels
Capillaries are specialized for diffusion.



A capillary is the smallest and thinnest tube in
the path of circulation and is specialized for
exchange of substances with interstitial fluid.
Total resistance is less than in arterioles so the
drop in blood pressure is not as great.
Venules and veins return blood to the heart.



Capillaries merge into venules.
Venules merge into veins.
Capillary
endothelium
Fig. 9.11c, p.166
Venule
connective
tissue coat
smooth
muscle
endothelium
Fig. 9.11d, p.166
Vein
connective
tissue coat
endothelium
valve
Fig. 9.11e, p.166
Structure and Functions of Blood Vessels
•
•

Veins are blood volume reservoirs (50-60% of blood
volume) because their walls can distend or contract.
Skeletal muscles adjacent to veins squeeze the walls
to move the blood along on its way back to the heart;
valves prevent backflow.
Varicose veins can form when the veins have
become overstretched, and the valves
weakened.
venous valve
Fig. 9.13a, p.167
blood flow to heart
valve
open
valve
closed
Fig. 9.13b,c, p.167
valve
closed
valve
closed
Fig. 9.13c, p.167
Structure and Functions of Blood Vessels
Vessels help control blood pressure.


The brain monitors signals from various arteries
to determine the rate of heartbeat and any
changes needed in vessel diameters.
•
•

If the blood pressure increases, the arterioles are
instructed to relax (vasodilation).
If the pressure decreases, the diameter of the
arterioles decreases (vasoconstriction).
In the baroreceptor reflex, special receptors in
the carotid arteries monitor changes in blood
pressure and send the information to the brain
for action.
(systolic)
Blood pressure (mm Hg)
120
80
(diastolic)
40
0
venules
Fig. 9.12, p.166
Section 7
Capillaries: Where Blood
Exchanges Substances
with Tissues
Capillaries: Where Blood Exchanges
Substances with Tissues
A vast network of capillaries weaves close
to nearly all living body cells.




Capillaries comprise most
of the cardiovascular
system.
The velocity of blood flow
slows as the diameter of the vessels
decreases.
It is slowest in the capillaries to provide for
maximum exchange.
Figure 9.14a
Capillaries: Where Blood Exchanges
Substances with Tissues
Many substances enter and leave
capillaries by diffusion.



Diffusion is a slow process and is not efficient
over long distances.
Billions of capillaries ensure that all cells are
near enough to a capillary to receive nutrients
and give up wastes;
blood flow is slow
enough here to allow
diffusion.
Figure 9.14b
Capillaries: Where Blood Exchanges
Substances with Tissues
Some substances pass through “pores” in
capillary walls.



Water-filled, slitlike areas between the cells of
capillary walls allow water-soluble substances
to exit the blood due to pressure (bulk flow).
This movement of fluids and solutes is
important to homeostasis and maintaining blood
pressure.
cell of
capillary wall
pores
Fig. 9.14c, p.168
blood to
venule
blood
from
arteriole
outward-directed
bulk flow
inward-directed
osmotic movement
cells of
tissue
Fig. 9.15, p.169
Capillaries: Where Blood Exchanges
Substances with Tissues
Blood in capillaries flows onward to venules.



Precapillary sphincters regulate the flow of
blood into capillaries.
Capillaries are the “turnaround points” for the
cardiovascular system.
arteriole
precapillary
sphincter
smooth muscle
capillary
venule
Fig. 9.16, p.169
Section 8
Cardiovascular
Disorders
Cardiovascular Disorders
Many factors may influence your chance of
developing a cardiovascular disorder.



Some risk factors include: family history,
hypertension, obesity, smoking, or simply age.
Inflammation, which leads to the production of
C-reactive protein by the liver, may also play a
role in cardiovascular disease.
Cardiovascular Disorders
Arteries can be clogged or weakened.


Arteriosclerosis is a hardening of the arteries.
When cholesterol and other lipids build up in
these hardened arteries, atherosclerosis
occurs.
•
•
Atherosclerotic plaques can impede blood flow.
Coronary arteries are narrow and vulnerable to
clogging with these plaques; chest pain (angina
pectoris) or heart attack may occur.
Fig. 9.17a, p.170
Fig. 9.17b, p.170
Cardiovascular Disorders
High blood levels of cholesterol can lead to
atherosclerosis.



Low-density lipoproteins (LDL or “bad”
cholesterol) carry cholesterol into the arterial
walls; high-density lipoproteins (HDL or
“good” cholesterol) remove it.
A total of 200 mg cholesterol per milliliter of
blood or less is considered acceptable for most
people.
Cardiovascular Disorders
Surgery may be needed to clear blocked
arteries.


Coronary bypass involves using a large vessel
from elsewhere in the body to bypass a
completely blocked artery in the heart.
aorta
coronary
artery
blockage
a shunt made of a
section taken from one
of the patient’s other
blood vessels
Fig. 9.17c, p.170
Cardiovascular Disorders



Laser angioplasty uses a laser to vaporize
plaques while balloon angioplasty uses small
balloons to flatten the plaques to open room in
the artery; a wire “stent” may be inserted to
keep the ballooned area open.
Statins are drugs designed to reduce the
amount of cholesterol in the blood.
Disease, injury, or defects can weaken artery
walls so they bulge outward due to blood
pressure, forming an aneurysm; aneurysms
can be fatal if the artery wall bursts.
Cardiovascular Disorders
Heart damage can lead to heart attack and
heart failure.



A heart attack is damage to or death of heart
muscle.
In heart failure, the heart is weak and does not
pump blood as efficiently.
Cardiovascular Disorders
Arrhythmias are abnormal heart rhythms.




Electrocardiograms (ECGs) are recordings of
the cardiac cycle and can be used to reveal
irregular heart rhythms.
Arrhythmias are irregular heart rhythms;
bradycardia is a below normal rhythm, while
tachycardia is an above normal rhythm.
Ventricular fibrillation occurs when the
ventricles contract haphazardly so that blood is
not pumped correctly; this can lead to cardiac
arrest.
Fig. 9.18, p.171
Cardiovascular Disorders
A heart-healthy lifestyle.



Lifestyle changes can greatly reduce the risk
of cardiovascular disease.
Diets low in fat and cholesterol, regular
exercise, and not smoking are three key
strategies.
Table 9.2, p.170