Download 9 Circulation1

The Circulatory System
(p. 268-281)
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How Does Gravity Affect Blood Circulation?
•  As with all land animals, the giraffe and the
corn snake are constantly subject to the force of
gravity
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•  The circulatory system
keeps blood pumping
despite gravity’s pull
– Muscle contractions help
blood travel uphill in the
veins of a giraffe’s long
legs
– The wriggling of the corn
snake squeezes its veins
and increases circulation
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Functions of circulatory system:
–  transports O2 and nutrients to cells (glucose)
–  takes away CO2 and other wastes (ammonia)
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Requires the action of:
•  Blood: fluid tissue that carries nutrients, wastes,
and other molecules
•  Heart: muscular force to move blood around the
body through blood vessels
**your circulatory system is composed of
96,000 km of blood vessels!!
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1. The Heart
- muscular organ; ~the size of your
fist
-surrounded by a fluid-filled
membrane: pericardium ,
which reduces friction
-in every minute, 5 liters of blood
cycles from the heart to the body
and back to the heart
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Chambers
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Chambers
•  Each side has two hollow , muscular chambers
which is separated by a wall called the septum
•  Two thin walled atria receive blood
•  Two thick walled ventricles pump out blood
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Valves
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Valves
•  Allow blood to flow in one direction only
•  AV valve: separates atria & ventricle
•  Semilunar valve: separates ventricles and
arteries
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• Tiny cords of tissue
anchor flaps of the
valves to the ventricle
walls
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Heart murmur: the sound created by an improperly
closing heart valve
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2. Blood Vessels (text p.270-271)
i) Arteries
  Carry oxygenated blood AWAY from the heart
(one exception: pulmonary artery is
deoxygenated )
  Walls are thick, strong and elastic
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 Walls are composed of three layers
Epithelium
Valve
Basement
membrane
Epithelium
Epithelium
Smooth
muscle
CAPILLARY
Connective
tissue
Smooth
muscle
Connective
tissue
ARTERY
VEIN
VENULE
ARTERIOLE
Figure 23.5
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atherosclerosis: degeneration of a blood vessel
caused by the accumulation of fat deposits
(cholesterol or triglycerides) along inside of vessel
walls
Connective
tissue
Smooth
muscle
Epithelium
Plaque
Figure 23.8B
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•  Pressure is
highest in the
arteries
– It drops to
zero by the
time the
blood
reaches the
veins
Systolic
pressure
Diastolic
pressure
Relative sizes and
numbers
of blood
vessels
Figure 23.9A
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ii) Arterioles
•  Smaller arteries
Aneurysm: a thin, weakened section of the wall of
an artery or vein that bulges outward and may burst.
Stroke: blocked arteriole delivering oxygen to brain
cells
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iii) Capillaries
•  Smallest vessel in body (microscopic, single
layer thick)
•  Red blood cells must pass through single file
•  Branch through tissues
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– Capillaries main function: the site of nutrients,
waste, and gas exchange, by diffusion,
between blood and tissue
Capillary
INTERSTITIAL
FLUID
Diffusion of
molecules
Tissue
cell
Figure 23.1B
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Bruise : capillaries under the skin have been broken
and spill out blood
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iv) Veins
•  Carry deoxygenated blood TOWARD the heart
(one exception: pulmonary vein)
•  Thin walled; carry blood under low pressure
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•  Contain valves which open in one direction only
•  Skeletal muscle contraction aids venous blood
flow
Direction of
blood flow
in vein
Valve (open)
Valve (closed)
Skeletal muscle
Figure 23.9B
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•  Three factors keep blood moving back to the
heart
– muscle contractions
– breathing
– one-way valves
Direction of
blood flow
in vein
Valve (closed)
Skeletal muscle
Valve (open)
Figure 23.9B
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Varicose Veins: valves become weakened, blood flows
backward and collects inside the vein, causing it to bulge
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3. Pathways of the Circulatory System
a) Pulmonary Circulation (pathway)
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•  Deoxygenated blood pumped from the right
side of the heart to the lungs via the pulmonary
arteries
•  Blood picks up oxygen
and travels back to the
left side of the heart via
the pulmonary veins
Lung capillaries
PULMONARY
CIRCUIT
•  The pulmonary arteries
are the only arteries that
are deoxygenated
•  The pulmonary veins
are the only veins that
are oxygenated
A
A
V
V
Right
Left
SYSTEMIC
CIRCUIT
Systemic capillaries
Figure 23.3B
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b) Systemic Circulation (pathway)
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•  Two large veins: the superior vena cava and
inferior vena cava return blood to the right side
of the heart
Lung capillaries
•  Left side of heart pumps
blood to the entire body
via the aorta (largest
artery)
PULMONARY
CIRCUIT
A
A
V
V
Right
Left
SYSTEMIC
CIRCUIT
Systemic capillaries
Figure 23.3B
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•  From the aorta, the blood is diverted to:
Lung capillaries
• 
upper body arteries
• 
lower body arteries
• 
hepatic-portal system
(starts with intestines
and finishes in liver)
PULMONARY
CIRCUIT
A
A
V
V
Right
Left
SYSTEMIC
CIRCUIT
Systemic capillaries
Figure 23.3B
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Hepatic Portal System:
Inferior
vena cava
Liver
Hepatic vein
Portal vein
Intestines
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Hepatic Portal System:
capillary beds of head
and upper extremities
(to pulmonary
circuit)
aorta
(from
pulmonary
circuit)
•  Carries blood from the
intestines to the liver
heart
•  Allows liver to store and
capillary beds of other
organs in thoracic cavity
detoxify substances from
digestive tract before they are
capillary bed of liver
carried to the body
Hepatic vein
capillary beds of intestines
Portal vein
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Hepatic Portal System:
Inferior
vena cava
Liver
Hepatic vein
Portal vein
Intestines
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Hepatic Portal System:
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c) Coronary Circulation (pathway)
•  Coronary arteries branch from the aorta into
smaller vessels that provide oxygen-rich blood
to the heart muscle
•  Oxygen-poor blood then flows away from the
heart muscle from capillaries to larger coronary
veins that enter the right ventricle
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4. Cardiovascular Disorders
coronary artery disease (arteriosclerosis):
accumulation of plaque (fatty deposits) in the
coronary arteries that lead to a reduction in blood
flow to the heart (p.277)
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Heart: normal
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Heart: abnormally enlarged
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angina: chest pain that is caused by reduced blood
supply (oxygen) to the heart tissue; weakening the
heart cells without killing them
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heart attack: lack of blood, and consequently
oxygen supply to the heart tissue; killing heart cells
coronary by-pass: -a surgical procedure in which
a blood vessel from another part of the body is
attached to a coronary artery so as to bypass an
area of blockage
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Pulmonary
artery
Aorta
Pulmonary
artery
Superior
vena cava
LEFT
ATRIUM
RIGHT
ATRIUM
Pulmonary
veins
Pulmonary
veins
Semilunar
valve
Semilunar
valve
Atrioventricular
valve
Atrioventricular
valve
Inferior
vena cava
RIGHT
VENTRICLE
LEFT
VENTRICLE
Figure 23.4A
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Superior
vena cava
Capillaries of
Head and arms
Pulmonary
artery
Capillaries
of right lung
Pulmonary
artery
Aorta
9
Capillaries
of left lung
6
2
3
3
4
11
Pulmonary
vein
RIGHT ATRIUM
RIGHT VENTRICLE
5
1
Pulmonary
vein
LEFT ATRIUM
LEFT VENTRICLE
10
Aorta
Inferior
vena cava
Capillaries of
abdominal organs
and legs
8
Figure 23.4B
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5. Control of the Heartbeat
•  The SA node (pacemaker) generates electrical
signals that trigger the contraction of the atria
(located at top of right atrium)
•  The AV node then relays these signals to the
ventricles
Pacemaker
(SA node)
Specialized
muscle fibers
AV node
Right
atrium
Right
ventricle
1
2
3
4
ECG
Figure 23.7
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artificial pacemaker: electrical device surgically
implanted which regulates the electrical impulses
www.vmth.ucdavis.edu/cardio/cases/case14/pacemaker.htm
Pacemaker
(SA node)
Specialized
muscle fibers
AV node
Right
atrium
Right
ventricle
1
2
ECG
3
4
Figure 23.7
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Heart with artificial
pacemaker
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•  An electrocardiogram (ECG) is a recording of
electrical changes in the skin resulting from the
electrical signals in the heart
– Control centers in the brain adjust heart rate to
body needs
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6. The Heart (Cardiac) Cycle: sequence of heart
chamber contraction/relaxation
•  Diastole: relaxation
– Blood flows from the
veins into the heart
chambers
1 Heart is
2 Atria
relaxed.
AV valves
are open.
contract.
•  Systole: contraction
0.1 sec
– The atria briefly
contract and fill the
ventricles with blood
– Then the ventricles
contract and propel
blood out
0.4 sec
0.3 sec
SYSTOLE
3 Ventricles
contract.
Semilunar
valves
are open.
DIASTOLE
Figure 23.6
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7. Heart Sounds
First sound( “lubb”) caused by closing both AV
valves
Second sound (“dubb”) caused by closing both
semilunar valves
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8. Cardiac Output and Stroke Volume (p. 275)
•  Heart rate: number of heart beats per minute (about
70)
•  Stroke volume: amount of blood leaving the heart
with each heartbeat (about 70 mL)
•  Cardiac output: amount of blood pumped by the heart
(mL/min)
cardiac output = heart rate x stroke volume
•  Average person’s cardiac output is 5 liters:
= 70 beats per min x 70 mL = 4900 mL/min
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Activity: Your Heart Performance Score
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9. Blood pressure
•  the contraction of the ventricles generates
pressure exerted by blood on the walls of a
blood vessel
•  Blood pressure depends on
– 1. The volume of blood flow (cardiac output)
– 2. The resistance to blood flow caused by the
narrow openings of arterioles
•  Any change that affects these two factors
will change blood pressure
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Systolic blood pressure:
•  Left ventricle pumps out blood; pressure rises
to a maximum of ~120 mm Hg
Diastolic blood pressure:
•  Left ventricle fills with blood; pressure falls to a
minimum of ~80 mm Hg
-Average blood pressure is 120/80
-healthier values may be lower, however it is possible
to have blood pressure too low
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hypertension: persistently high blood pressure
with systolic 140 or greater and diastolic 90 or
greater
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Why is hypertension a problem?
•  The heart must work harder to pump blood
which can cause it to enlarge and become
weaker -----> coronary artery disease
•  Accelerates atherosclerosis
•  There is an increased force on blood vessels,
which can cause them to weaken ----> rupture
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Life style changes to reduce hypertension:
•  Exercise
•  Lose weight
•  Reduce intake of sodium (salt)
•  Maintain a balanced diet
•  Don’t smoke
•  Manage stress
•  Limit alcohol intake
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Blood Pressure Lab
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BIOLOGY
Blood Pressure
CONCEPTS & CONNECTIONS
Fourth Edition
Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor
The force exerted by blood against the inner
walls of blood vessels
(usually refers to pressure in large systemic arteries)
From PowerPoint® Lectures for Biology: Concepts & Connections
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When the cuff is inflated so that
it stops arterial blood flow, no
sound can be heard through a
stethoscope placed over the
brachial artery distal to the cuff.
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Korotkoff sounds are created by
pulsatile blood flow through the
compressed artery
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Blood flow is silent when the
artery is no longer compressed.
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Plastination by
Gunther von Hagen:
professor of anatomy
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Professor of
Anatomy:
Gunther von
Hagen
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