Download Chapter 23

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
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Tubular heart
Pores
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
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Capillary beds
Arteriole
Artery
(O2-rich blood)
Venule
Vein
Atrium
Ventricle
Gill
capillaries
Artery
(O2-poor blood)
Heart
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
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Gill capillaries
Heart:
Ventricle (V)
Atrium (A)
Systemic capillaries
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
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Lung and skin capillaries
Pulmocutaneous
circuit
A
A
V
Left
Right
Systemic
circuit
Systemic capillaries
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
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Lung capillaries
Pulmonary
circuit
A
A
V
V
Left
Right
Systemic
circuit
Systemic capillaries
THE HUMAN
CARDIOVASCULAR
SYSTEM
Copyright © 2009 Pearson Education, Inc.
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
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8
Superior
vena cava
Capillaries of
head, chest, and
arms
Pulmonary
artery
Pulmonary
artery
Capillaries
of right lung
9
Capillaries
of left lung
Aorta
2
7
2
3
3
4
5
10
4
Pulmonary
vein
Right atrium
6
1
9
Pulmonary
vein
Left atrium
Left ventricle
Right ventricle
Inferior
vena cava
Aorta
8
Capillaries of
abdominal region
and legs
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
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Right
atrium
To lung
To lung
Left atrium
From lung
From lung
Semilunar
valve
Semilunar
valve
Atrioventricular
(AV) valve
Atrioventricular
(AV) valve
Right
ventricle
Left
ventricle
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
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1
Semilunar
valves
Heart is closed
relaxed.
AV valves
are open.
0.4 sec
Diastole
2
1
Semilunar
valves
Heart is closed
relaxed.
Atria
contract.
0.1 sec
Systole
AV valves
are open.
0.4 sec
Diastole
2
1
Semilunar
valves
Heart is closed
relaxed.
Atria
contract.
0.1 sec
Systole
AV valves
are open.
0.4 sec
0.3 sec
3
Ventricles
contract.
Semilunar
valves
are open.
Diastole
AV valves
closed
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
Copyright © 2009 Pearson Education, Inc.
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
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Pacemaker
(SA node)
AV node
Specialized
muscle fibers
Right
atrium
Apex
1 Pacemaker
generates
signals
to contract
ECG
2 Signals spread
through atria
and are delayed
at AV node
3 Signals relayed
to apex of heart
4 Signals spread
through
ventricle
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
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Heart
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
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Superior
vena cava
Pulmonary
artery
Right
coronary
artery
Aorta
Left
coronary
artery
Blockage
Dead
muscle
tissue
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
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Connective Smooth
tissue
muscle Epithelium
Plaque
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
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Epithelium
Epithelium
Smooth
muscle
Connective
tissue
Capillary
Basal lamina
Valve
Epithelium
Smooth
muscle
Connective
tissue
Artery
Vein
Arteriole
Venule
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
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Red
blood
cell
Capillary
Nuclei of
smooth
muscle
cells
Capillary
Interstitial
fluid
Tissue
cell
Diffusion of
molecules
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
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Pressure (mm Hg)
120
100
80
60
40
20
0
Systolic
pressure
Diastolic
pressure
Venae cavae
Veins
Venules
Capillaries
Arterioles
Arteries
50
40
30
20
10
0
Aorta
Velocity (cm/sec)
Relative sizes and
numbers
of blood
vessels
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
Copyright © 2009 Pearson Education, Inc.
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
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Direction of
blood flow
in vein
Valve
(open)
Skeletal
muscle
Valve
(closed)
23.9 CONNECTION: Measuring blood pressure
can reveal cardiovascular problems
 Hypertension is a serious cardiovascular problem
– Consistent pressures above either
– 140 systolic
– 90 diastolic
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Typical blood
pressure
120 systolic
70 diastolic
Pressure
in cuff
above 120
120
Rubber cuff
inflated
with air
Artery
1
Pressure
in cuff
at 70
Pressure
in cuff
at 120
120
70
Sounds
audible in
stethoscope
Artery
closed
2
3
Sounds
stop
4
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
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Precapillary sphincters Thoroughfare
channel
Arteriole
1
Capillaries
Venule
Sphincters relaxed
Thoroughfare
channel
Arteriole
2
Sphincters contracted
Venule
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
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Capillary
lumen
Capillary
wall
Interstitial
fluid
Nucleus of
epithelial
cell
Muscle Clefts between
cell
the epithelial
cells of the
capillary wall
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
Copyright © 2009 Pearson Education, Inc.
Tissue cells
Blood
pressure
Interstitial
fluid
Osmotic
pressure
Osmotic
pressure
Arterial
end of
capillary
Net fluid
movement out
Blood
pressure
Net fluid
movement in
Venous
end of
capillary
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
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Plasma (55%)
Constituent
Major functions
Water
Solvent for
carrying other
substances
Ions (blood electrolytes)
Osmotic balance,
pH buffering, and
maintaining ion
concentration of
interstitial fluid
Sodium
Potassium
Calcium
Magnesium
Chloride
Bicarbonate
Plasma proteins
Cellular elements (45%)
Cell type
Functions
Number
per µL (mm3) of blood
Erythrocytes
(red blood cells)
5–6 million
Centrifuged
blood
sample
Leukocytes
5,000–10,000
(white blood cells)
Transport of
oxygen (and
carbon dioxide)
Defense and
immunity
Osmotic balance
and pH buffering
Fibrinogen
Clotting
Immunoglobulins
(antibodies)
Defense
Substances transported by blood
Nutrients (e.g., glucose, fatty acids, vitamins)
Waste products of metabolism
Respiratory gases (O2 and CO2)
Hormones
Lymphocyte
Basophil
Eosinophil
Neutrophil
Platelets
Monocyte
250,000–
400,000
Blood clotting
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
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1
Platelets adhere
to exposed
connective tissue
Epithelium
Connective
tissue
Platelet
1
Platelets adhere
to exposed
connective tissue
2
Platelet plug
forms
Epithelium
Connective
tissue
Platelet
Platelet plug
1
Platelets adhere
to exposed
connective tissue
2
Platelet plug
forms
3
Epithelium
Connective
tissue
Platelet
Platelet plug
Fibrin clot
traps
blood cells
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
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Multipotent
stem cell
Lymphoid
stem cell
Myeloid
stem cells
Erythrocytes
Platelets
Lymphocytes
Basophils
Eosinophils
Monocytes Neutrophils
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
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Capillary
Epithelium
Basement
membrane
Valve
Smooth
muscle
Connective
tissue
Artery
Vein
p.
a.
o.
c.
b.
n.
d.
m.
e.
l.
f.
k.
g.
j.
h.
i.
a.
b.
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
Copyright © 2009 Pearson Education, Inc.
You should now be able to
9. Describe the process of blood clotting
10. Describe the causes and treatments for leukemia
Copyright © 2009 Pearson Education, Inc.