copyright © 2009 pearson education, inc. mechanisms of internal transport
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Copyright © 2009 Pearson Education, Inc.
MECHANISMS OF INTERNAL TRANSPORT
Copyright © 2009 Pearson Education, Inc.
23.1 Circulatory systems facilitate exchange with all body tissues
All cells need
– Nutrients
– Gas exchange
– Removal of wastes
Diffusion alone is inadequate for large and complex bodies
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23.1 Circulatory systems facilitate exchange with all body tissues
An internal transport system assists diffusion by moving materials between
– Surfaces of the body
– Internal tissues
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23.1 Circulatory systems facilitate exchange with all body tissues
A gastrovascular cavity in cnidarians and flatworms serves
– Digestion
– Distribution of substances
Most animals use a circulatory system
– Blood
– Heart
– Blood vessels
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23.1 Circulatory systems facilitate exchange with all body tissues
Open circulatory systems
– Arthropods and many molluscs
– Heart pumps blood through open-ended vessels
– Cells directly bathed in blood
PoresTubular heart
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23.1 Circulatory systems facilitate exchange with all body tissues
Closed circulatory systems
– Vertebrates, earthworms, squids, octopuses
– Blood stays confined to vessels
– A heart pumps blood through arteries to capillaries
– Veins return blood to heart
Capillary beds
Artery(O2-rich blood)
Arteriole
Artery(O2-poor blood)
HeartVentricle
Atrium
Vein
Venule
Gillcapillaries
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23.2 EVOLUTION CONNECTION: Vertebrate Cardiovascular systems reflect evolution
Two-chambered heart
– Fish
– Pumps blood in a single circuit
– From gill capillaries
– To systemic capillaries
– Back to heart
Gill capillaries
Heart:
Ventricle (V)
Atrium (A)
Systemic capillaries
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23.2 EVOLUTION CONNECTION: Vertebrate Cardiovascular systems reflect evolution
Land vertebrates have double circulation
– Separate pulmonary and systemic circuits
Three-chambered hearts
– Amphibians, turtles, snakes, lizards
– Two atria
– One undivided ventricle
– Permits blood diversion away from lungs when diving
– But some blood from body and lungs mixes in the ventricle when not diving
Lung and skin capillaries
Pulmocutaneouscircuit
VRight
Systemic capillaries
A A
LeftSystemic
circuit
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23.2 EVOLUTION CONNECTION: Vertebrate Cardiovascular systems reflect evolution
Four-chambered hearts
– Crocodilians, birds, mammals
– Two atria and two ventricles
– Two circuits that do not mix
– Right side pumps blood from body to lungs
– Left side pumps blood from lungs to body
– Higher blood pressure
– Supports more efficient movement of blood
– Needed in endothermic animals
Lung capillaries
Pulmonarycircuit
VRight
Systemic capillaries
A A
LeftSystemic
circuit
V
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THE HUMAN CARDIOVASCULAR
SYSTEM
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23.3 The human cardiovascular system illustrates the double circulation of mammals
Blood flow through the double circulatory system of humans
Animation: Path of Blood Flow in Mammals
Superiorvena cava
Pulmonaryartery
Capillariesof right lung
8
9
2
3
Aorta
4 510
16
Pulmonaryvein
9Right atrium
Inferiorvena cava
Right ventricle
4
8
3
Pulmonaryartery
Capillariesof left lung
Aorta
Pulmonaryvein
Left atrium
Left ventricle
27
Capillaries ofhead, chest, andarms
Capillaries ofabdominal regionand legs
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23.3 The human cardiovascular system illustrates the double circulation of mammals
The mammalian heart
– Two thin-walled atria that
– Pump blood
– To ventricles
– Thick-walled ventricles that
– Pump blood
– To lungs and all other body regions
Right atrium To lung
From lung
Semilunarvalve
Atrioventricular(AV) valve
Left atrium
To lung
From lung
Semilunarvalve
Atrioventricular(AV) valve
Rightventricle
Leftventricle
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23.4 The heart contracts and relaxes rhythmically
During diastole, blood flows
– From veins
– Into heart chambers
During systole, blood flows
– From atria
– Into ventricles
Semilunarvalvesclosed1 Heart is
relaxed.
AV valvesare open.
Diastole
0.4 sec
Semilunarvalvesclosed1 Heart is
relaxed.
AV valvesare open.
Diastole
0.4 sec
2 Atriacontract.
Systole0.1 sec
Semilunarvalvesclosed1 Heart is
relaxed.
AV valvesare open.
Diastole
0.4 sec
2 Atriacontract.
Systole0.1 sec
Semilunarvalvesare open.
3 Ventriclescontract.
AV valvesclosed
0.3 sec
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23.4 The heart contracts and relaxes rhythmically
Cardiac output
– Amount of blood/minute pumped into systemic circuit
Heart rate
– Number of beats/minute
Heart valves
– Prevent the backflow of blood
Heart murmur
– A defect in one or more heart valves
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23.5 The pacemaker sets the tempo of the heartbeat
The pacemaker (SA node)
– Sets the rate of heart contractions
– Generates electrical signals in atria
The AV node
– Relays these signals to the ventricles
Pacemaker(SA node) AV node
Rightatrium
1 Pacemakergeneratessignalsto contract
2 Signals spreadthrough atriaand are delayedat AV node
ECG
3 Signals relayedto apex of heart
4 Signals spreadthroughventricle
Apex
Specializedmuscle fibers
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23.5 The pacemaker sets the tempo of the heartbeat
An electrocardiogram (ECG)
– Records electrical changes in heart
Heart rate normally adjusts to body needs
Abnormal rhythms may occur in a heart attack
– External defibrillator can restore rhythm
– Implanted artificial pacemakers can trigger normal rhythms
Heart
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23.6 CONNECTION: What is a heart attack?
A heart attack is damage to cardiac muscle
– Typically from a blocked coronary artery
Stroke
– Death of brain tissue from blocked arteries in the head
Blockage
Deadmuscletissue
Rightcoronaryartery
Superiorvena cava
Pulmonaryartery
Aorta
Leftcoronaryartery
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23.6 CONNECTION: What is a heart attack?
Atherosclerosis
– Plaques develop inside inner walls of blood vessels
– Plaques narrow blood vessels
– Blood flow is reduced
PlaqueEpitheliumConnectivetissue
Smoothmuscle
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23.7 The structure of blood vessels fits their functions
Arteries and veins
– Lined by single layer of epithelial cells
– Smooth muscle in walls can reduce blood flow
– Elastic fibers permit recoil after stretching
– Veins have one-way valves that restrict backward flow
Connectivetissue
Capillary
Venule
Smoothmuscle
Arteriole
Artery Vein
Valve
Epithelium
Basal lamina
Epithelium
Smoothmuscle
Epithelium
Connectivetissue
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23.7 The structure of blood vessels fits their functions
Capillaries
– Thin walls—a single layer of epithelial cells
– Narrow—blood cells flow in a single file
– Increase surface area for gas and fluid exchange
Nuclei ofsmoothmusclecells
Redbloodcell
Capillary
Diffusion ofmolecules
Capillary
Interstitialfluid
Tissuecell
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23.8 Blood pressure and velocity reflect the structure and arrangement of blood vessels
Blood pressure
– The force blood exerts on vessel walls
– Depends on
– Cardiac output
– Resistance of vessels
– Decreases as blood moves away from heart
Systolicpressure
Diastolicpressure
120100
806040200
Relative sizes andnumbersof bloodvessels
Pre
ssu
re (
mm
Hg
)V
elo
city
(cm
/sec
)
5040302010
0
Ao
rta
Ven
ae c
avae
Art
erie
s
Cap
illar
ies
Ven
ule
s
Vei
ns
Art
erio
les
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23.8 Blood pressure and velocity reflect the structure and arrangement of blood vessels
Blood pressure is
– Highest in arteries
– Lowest in veins
Blood pressure is measured as
– Systolic pressure—caused by ventricular contraction
– Diastolic pressure—low pressure between contractions
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23.8 Blood pressure and velocity reflect the structure and arrangement of blood vessels
How does blood travel against gravity, up legs?
– Pressure from muscle contractions
– Between two muscles
– Between muscles and bone or skin
– Squeezes veins
– One-way valves limit blood flow to one direction, towards heart
Direction ofblood flowin vein
Valve(open)
Skeletalmuscle
Valve(closed)
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23.9 CONNECTION: Measuring blood pressure can reveal cardiovascular problems
Hypertension is a serious cardiovascular problem
– Consistent pressures above either
– 140 systolic
– 90 diastolic
Typical bloodpressure120 systolic70 diastolic
Pressurein cuffabove 120120Rubber cuff
inflatedwith air
Arteryclosed
Artery
1 2
Pressurein cuffat 120120
Soundsaudible instethoscope
3
70
Soundsstop
4
Pressurein cuffat 70
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23.9 CONNECTION: Measuring blood pressure can reveal cardiovascular problems
Hypertension causes
– Heart to work harder, weakening heart over time
– Increased plaque formation from tiny ruptures
– Increased risk of blood clot formation
Hypertension can cause
– Heart attacks
– Strokes
– Kidney failure
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23.10 Smooth muscle controls the distribution of blood
Blood flow through capillaries– Is restricted by smooth muscle sphincters
– Only about 5–10% of capillaries are open at one time
Capillaries
Thoroughfarechannel
Precapillary sphincters
Venule
Sphincters relaxed
Thoroughfarechannel
VenuleArteriole
2
1
Sphincters contracted
Arteriole
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23.11 Capillaries allow the transfer of substances through their walls
Capillaries have very thin walls
Substances can cross through these thin walls
– Between blood and interstitial fluids
Nucleus ofepithelial
cell
Capillarylumen
Interstitialfluid
Capillarywall
Musclecell
Clefts betweenthe epithelialcells of thecapillary wall
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23.11 Capillaries allow the transfer of substances through their walls
Blood and interstitial fluid exchange substances
– By diffusion
– By pressure flow through clefts between epithelial cells
Blood pressure forces fluid out of capillaries at the arterial end
Osmotic pressure draws in fluid at the venous end
Tissue cells
Osmoticpressure
Interstitialfluid
Net fluidmovement in
Bloodpressure
Osmoticpressure Venous
end ofcapillary
Arterialend of
capillary
Bloodpressure
Net fluidmovement out
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STRUCTURE AND FUNCTION
OF BLOOD
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23.12 Blood consists of red and white blood cells suspended in plasma
Plasma is about 90% water
Plasma contains
– Various inorganic ions
– Proteins, nutrients
– Wastes, gases
– Hormones
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23.12 Blood consists of red and white blood cells suspended in plasma
Red blood cells (erythrocytes)
– Transport O2 bound to hemoglobin
White blood cells (leukocytes)
– Function inside and outside the circulatory system
– Fight infections and cancer
Plasma (55%)
Constituent
Osmotic balance,pH buffering, andmaintaining ionconcentration ofinterstitial fluid
Solvent forcarrying othersubstances
Water
Ions (blood electrolytes)
Major functions
SodiumPotassiumCalciumMagnesiumChlorideBicarbonate
Plasma proteins
ClottingFibrinogen
Osmotic balanceand pH buffering
Defense Immunoglobulins(antibodies)
Substances transported by blood
Nutrients (e.g., glucose, fatty acids, vitamins)Waste products of metabolismRespiratory gases (O2 and CO2)Hormones
Cellular elements (45%)
Centrifugedblood
sample
Numberper µL (mm3) of blood
Cell type Functions
Erythrocytes(red blood cells) 5–6 million Transport of
oxygen (andcarbon dioxide)
Leukocytes(white blood cells)
BasophilLymphocyte
Defense andimmunity
Eosinophil
5,000–10,000
250,000–400,000
Neutrophil Monocyte
Blood clottingPlatelets
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23.14 Blood clots plug leaks when blood vessels are injured
The blood-clotting process
– Platelets adhere to exposed connective tissue
– Platelets form a plug
– Platelets help trigger the conversion of fibrinogen to fibrin
– A fibrin clot traps blood cells
Platelets adhereto exposedconnective tissue
1
Epithelium
Connective tissue
Platelet
Platelets adhereto exposedconnective tissue
1
Epithelium
Connective tissue
Platelet
Platelet plugforms
2
Platelet plug
Platelets adhereto exposedconnective tissue
1
Epithelium
Connective tissue
Platelet
Platelet plugforms
2
Platelet plug
Fibrin clottrapsblood cells
3
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23.13 CONNECTION: Too few or too many red blood cells can be unhealthy
Anemia
– Abnormally low amounts of hemoglobin or red blood cells
– Causes fatigue due to lack of oxygen in tissues
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23.13 CONNECTION: Too few or too many red blood cells can be unhealthy
Hormone erythropoietin (EPO)
– Regulates red blood cell production
Some athletes artificially increase red blood cell production by injecting erythropoietin
– Can lead to
– Clotting
– Stroke
– Heart failure
– Death
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23.15 CONNECTION: Stem cells offer a potential cure for blood cell diseases
Stem cells divide in bone marrow
– To produce all the types of blood cells throughout life
– Are used to treat some blood disorders
Multipotentstem cell
Lymphoidstem cell
Myeloidstem cells
Erythrocytes
PlateletsEosinophils
Basophils
NeutrophilsMonocytesLymphocytes
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23.15 CONNECTION: Stem cells offer a potential cure for blood cell diseases
Leukemia is cancer of white blood cells
– Leukemia results in extra leukocytes that do not function properly
– Leukemia is usually fatal unless treated
– Some treatments
– Destroy all bone marrow in the patient
– Transplant new bone marrow from a donor with similar bone marrow
Capillary
EpitheliumValve
Basementmembrane
Connectivetissue
Smoothmuscle
VeinArtery
a.
c.
d.
e.
f.
g.
h.
i.
b.
p.
o.
n.
m.
l.
k.
j.
a.
b.
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You should now be able to
1. Explain how the circulatory systems of a giraffe and snake resist gravity
2. Describe the general need for and functions of a circulatory system
3. Compare the structures and functions of gastrovascular cavities, open circulatory systems, and closed circulatory systems
4. Compare the circulatory systems of a fish, frog, and mammal
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You should now be able to
5. Explain how heartbeats are controlled
6. Describe the causes and consequences of a heart attack and cardiovascular disease
7. Relate the structure of blood vessels to their functions
8. Describe the components of blood and their functions
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You should now be able to
9. Describe the process of blood clotting
10. Describe the causes and treatments for leukemia