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LECTURE PRESENTATIONS
For CAMPBELL BIOLOGY, NINTH EDITION
Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson
Chapter 42
Circulation and Gas Exchange
Lectures by
Erin Barley
Kathleen Fitzpatrick
© 2011 Pearson Education, Inc.
Overview: Trading Places
• Every organism must exchange materials with its
environment
• Exchanges ultimately occur at the cellular level by
crossing the plasma membrane
• In unicellular organisms, these exchanges occur
directly with the environment
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• For most cells making up multicellular organisms,
direct exchange with the environment is not
possible
• Gills are an example of a specialized exchange
system in animals
– O2 diffuses from the water into blood vessels
– CO2 diffuses from blood into the water
• Internal transport and gas exchange are
functionally related in most animals
© 2011 Pearson Education, Inc.
Figure 42.1
Concept 42.1: Circulatory systems link
exchange surfaces with cells throughout
the body
• Diffusion time is proportional to the square of the
distance
• Diffusion is only efficient over small distances
• In small and/or thin animals, cells can exchange
materials directly with the surrounding medium
• In most animals, cells exchange materials with the
environment via a fluid-filled circulatory system
© 2011 Pearson Education, Inc.
Gastrovascular Cavities
• Some animals lack a circulatory system
• Some cnidarians, such as jellies, have elaborate
gastrovascular cavities
• A gastrovascular cavity functions in both digestion
and distribution of substances throughout the body
• The body wall that encloses the gastrovascular
cavity is only two cells thick
• Flatworms have a gastrovascular cavity and a
large surface area to volume ratio
© 2011 Pearson Education, Inc.
Figure 42.2
Circular
canal
Mouth
Gastrovascular
cavity
Mouth
Pharynx
Radial canals
5 cm
(a) The moon jelly Aurelia, a cnidarian
2 mm
(b) The planarian Dugesia, a flatworm
Figure 42.2a
Circular
canal
Radial canals
Mouth
5 cm
(a) The moon jelly Aurelia, a cnidarian
Figure 42.2b
Gastrovascular
cavity
Mouth
Pharynx
2 mm
(b) The planarian Dugesia, a flatworm
Evolutionary Variation in Circulatory
Systems
• A circulatory system minimizes the diffusion
distance in animals with many cell layers
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General Properties of Circulatory Systems
• A circulatory system has
– A circulatory fluid
– A set of interconnecting vessels
– A muscular pump, the heart
• The circulatory system connects the fluid that
surrounds cells with the organs that exchange
gases, absorb nutrients, and dispose of wastes
• Circulatory systems can be open or closed and
vary in the number of circuits in the body
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Open and Closed Circulatory Systems
• In insects, other arthropods, and most molluscs,
blood bathes the organs directly in an open
circulatory system
• In an open circulatory system, there is no
distinction between blood and interstitial fluid, and
this general body fluid is called hemolymph
© 2011 Pearson Education, Inc.
Figure 42.3
(a) An open circulatory system
(b) A closed circulatory system
Heart
Heart
Interstitial fluid
Hemolymph in sinuses
surrounding organs
Pores
Blood
Small branch
vessels in
each organ
Dorsal
Auxiliary
vessel
hearts
(main heart)
Tubular heart
Ventral vessels
Figure 42.3a
(a) An open circulatory system
Heart
Hemolymph in sinuses
surrounding organs
Pores
Tubular heart
• In a closed circulatory system, blood is
confined to vessels and is distinct from the
interstitial fluid
• Closed systems are more efficient at transporting
circulatory fluids to tissues and cells
• Annelids, cephalopods, and vertebrates have
closed circulatory systems
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Figure 42.3b
(b) A closed circulatory system
Heart
Interstitial fluid
Blood
Small branch
vessels in
each organ
Dorsal
Auxiliary
vessel
hearts
(main heart)
Ventral vessels
Organization of Vertebrate Circulatory
Systems
• Humans and other vertebrates have a closed
circulatory system called the cardiovascular
system
• The three main types of blood vessels are arteries,
veins, and capillaries
• Blood flow is one way in these vessels
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• Arteries branch into arterioles and carry blood
away from the heart to capillaries
• Networks of capillaries called capillary beds are
the sites of chemical exchange between the blood
and interstitial fluid
• Venules converge into veins and return blood
from capillaries to the heart
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• Arteries and veins are distinguished by the
direction of blood flow, not by O2 content
• Vertebrate hearts contain two or more chambers
• Blood enters through an atrium and is pumped
out through a ventricle
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Single Circulation
• Bony fishes, rays, and sharks have single
circulation with a two-chambered heart
• In single circulation, blood leaving the heart
passes through two capillary beds before returning
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Figure 42.4
(a) Single circulation
(b) Double circulation
Pulmonary circuit
Gill
capillaries
Lung
capillaries
Artery
Heart:
A
Atrium (A)
V
Right
Ventricle (V)
A
V
Left
Vein
Systemic
capillaries
Body
capillaries
Systemic circuit
Key
Oxygen-rich blood
Oxygen-poor blood
Figure 42.4a
(a) Single circulation
Gill
capillaries
Artery
Heart:
Atrium (A)
Ventricle (V)
Vein
Body
capillaries
Key
Oxygen-rich blood
Oxygen-poor blood
Double Circulation
• Amphibian, reptiles, and mammals have double
circulation
• Oxygen-poor and oxygen-rich blood are pumped
separately from the right and left sides of the heart
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Figure 42.4b
(b) Double circulation
Pulmonary circuit
Lung
capillaries
A
V
Right
A
V
Left
Systemic
capillaries
Key
Systemic circuit
Oxygen-rich blood
Oxygen-poor blood
• In reptiles and mammals, oxygen-poor blood flows
through the pulmonary circuit to pick up oxygen
through the lungs
• In amphibians, oxygen-poor blood flows through a
pulmocutaneous circuit to pick up oxygen
through the lungs and skin
• Oxygen-rich blood delivers oxygen through the
systemic circuit
• Double circulation maintains higher blood pressure
in the organs than does single circulation
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Adaptations of Double Circulatory Systems
• Hearts vary in different vertebrate groups
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Amphibians
• Frogs and other amphibians have a threechambered heart: two atria and one ventricle
• The ventricle pumps blood into a forked artery that
splits the ventricle’s output into the
pulmocutaneous circuit and the systemic circuit
• When underwater, blood flow to the lungs is nearly
shut off
© 2011 Pearson Education, Inc.
Figure 42.5a
Amphibians
Pulmocutaneous circuit
Lung
and skin
capillaries
Atrium
(A)
Atrium
(A)
Right
Left
Ventricle (V)
Systemic
capillaries
Systemic circuit
Key
Oxygen-rich blood
Oxygen-poor blood
Reptiles (Except Birds)
• Turtles, snakes, and lizards have a threechambered heart: two atria and one ventricle
• In alligators, caimans, and other crocodilians a
septum divides the ventricle
• Reptiles have double circulation, with a pulmonary
circuit (lungs) and a systemic circuit
© 2011 Pearson Education, Inc.
Figure 42.5b
Reptiles (Except Birds)
Pulmonary circuit
Lung
capillaries
Right
systemic
aorta
Atrium
(A)
Ventricle
(V)
A
Right
V
Left
Left
systemic
aorta
Incomplete
septum
Systemic
capillaries
Systemic circuit
Key
Oxygen-rich blood
Oxygen-poor blood
Mammals and Birds
• Mammals and birds have a four-chambered heart
with two atria and two ventricles
• The left side of the heart pumps and receives only
oxygen-rich blood, while the right side receives
and pumps only oxygen-poor blood
• Mammals and birds are endotherms and require
more O2 than ectotherms
© 2011 Pearson Education, Inc.
Figure 42.5c
Mammals and Birds
Pulmonary circuit
Lung
capillaries
A
Atrium
(A)
Ventricle
(V)
Right
V
Left
Systemic
capillaries
Systemic circuit
Key
Oxygen-rich blood
Oxygen-poor blood
Figure 42.5
Amphibians
Pulmocutaneous circuit
Pulmonary circuit
Lung
and skin
capillaries
Atrium
(A)
Atrium
(A)
Right
Pulmonary circuit
Lung
capillaries
Lung
capillaries
Right
systemic
aorta
A
V
Right
Left
Mammals and Birds
Reptiles (Except Birds)
A
V
Left
Left
systemic
aorta
Incomplete
septum
A
V
Right
A
V
Left
Ventricle (V)
Systemic circuit
Key
Oxygen-rich blood
Oxygen-poor blood
Systemic
capillaries
Systemic
capillaries
Systemic
capillaries
Systemic circuit
Systemic circuit
Concept 42.2: Coordinated cycles of heart
contraction drive double circulation in
mammals
• The mammalian cardiovascular system meets the
body’s continuous demand for O2
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Mammalian Circulation
• Blood begins its flow with the right ventricle
pumping blood to the lungs
• In the lungs, the blood loads O2 and unloads CO2
• Oxygen-rich blood from the lungs enters the heart
at the left atrium and is pumped through the aorta
to the body tissues by the left ventricle
• The aorta provides blood to the heart through the
coronary arteries
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• Blood returns to the heart through the superior
vena cava (blood from head, neck, and forelimbs)
and inferior vena cava (blood from trunk and hind
limbs)
• The superior vena cava and inferior vena cava
flow into the right atrium
Animation: Path of Blood Flow in Mammals
© 2011 Pearson Education, Inc.
Figure 42.6
Capillaries of
head and forelimbs
Superior vena cava
Pulmonary
artery
Capillaries
of right lung
Pulmonary
vein
Right atrium
Right ventricle
Pulmonary
artery
Aorta
Capillaries
of left lung
Pulmonary vein
Left atrium
Left ventricle
Aorta
Inferior
vena cava
Capillaries of
abdominal organs
and hind limbs
The Mammalian Heart: A Closer Look
• A closer look at the mammalian heart provides a
better understanding of double circulation
© 2011 Pearson Education, Inc.
Figure 42.7
Aorta
Pulmonary artery
Pulmonary
artery
Right
atrium
Left
atrium
Semilunar
valve
Semilunar
valve
Atrioventricular
valve
Atrioventricular
valve
Right
ventricle
Left
ventricle
• The heart contracts and relaxes in a rhythmic
cycle called the cardiac cycle
• The contraction, or pumping, phase is called
systole
• The relaxation, or filling, phase is called diastole
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Figure 42.8-1
1 Atrial and
ventricular diastole
0.4
sec
Figure 42.8-2
2 Atrial systole and ventricular
diastole
1 Atrial and
ventricular diastole
0.1
sec
0.4
sec
Figure 42.8-3
2 Atrial systole and ventricular
diastole
1 Atrial and
ventricular diastole
0.1
sec
0.4
sec
0.3 sec
3 Ventricular systole and atrial
diastole
• The heart rate, also called the pulse, is the
number of beats per minute
• The stroke volume is the amount of blood
pumped in a single contraction
• The cardiac output is the volume of blood
pumped into the systemic circulation per minute
and depends on both the heart rate and stroke
volume
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• Four valves prevent backflow of blood in the heart
• The atrioventricular (AV) valves separate each
atrium and ventricle
• The semilunar valves control blood flow to the
aorta and the pulmonary artery
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• The “lub-dup” sound of a heart beat is caused by
the recoil of blood against the AV valves (lub) then
against the semilunar (dup) valves
• Backflow of blood through a defective valve
causes a heart murmur
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Maintaining the Heart’s Rhythmic Beat
• Some cardiac muscle cells are self-excitable,
meaning they contract without any signal from the
nervous system
• The sinoatrial (SA) node, or pacemaker, sets the
rate and timing at which cardiac muscle cells
contract
• Impulses that travel during the cardiac cycle can
be recorded as an electrocardiogram (ECG or
EKG)
© 2011 Pearson Education, Inc.
Figure 42.9-1
1
SA node
(pacemaker)
ECG
Figure 42.9-2
1
SA node
(pacemaker)
ECG
2
AV
node
Figure 42.9-3
1
SA node
(pacemaker)
ECG
2
AV
node
3
Bundle
branches
Heart
apex
Figure 42.9-4
1
SA node
(pacemaker)
ECG
2
AV
node
3
Bundle
branches
4
Heart
apex
Purkinje
fibers
• Impulses from the SA node travel to the
atrioventricular (AV) node
• At the AV node, the impulses are delayed and
then travel to the Purkinje fibers that make the
ventricles contract
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• The pacemaker is regulated by two portions of the
nervous system: the sympathetic and
parasympathetic divisions
• The sympathetic division speeds up the
pacemaker
• The parasympathetic division slows down the
pacemaker
• The pacemaker is also regulated by hormones
and temperature
© 2011 Pearson Education, Inc.
Concept 42.3: Patterns of blood pressure and
flow reflect the structure and arrangement
of blood vessels
• The physical principles that govern
movement of water in plumbing systems also
influence the functioning of animal circulatory
systems
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Blood Vessel Structure and Function
• A vessel’s cavity is called the central lumen
• The epithelial layer that lines blood vessels is
called the endothelium
• The endothelium is smooth and minimizes
resistance
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Figure 42.10
Vein
LM
Artery
Red blood cells
100 m
Valve
Basal lamina
Endothelium
Smooth
muscle
Connective
tissue
Endothelium
Capillary
Smooth
muscle
Connective
tissue
Artery
Vein
Capillary
15 m
Red blood cell
Venule
LM
Arteriole
Figure 42.10a
Valve
Basal lamina
Endothelium
Smooth
muscle
Connective
tissue
Endothelium
Capillary
Smooth
muscle
Connective
tissue
Artery
Vein
Arteriole
Venule
Figure 42.10b
Vein
LM
Artery
Red blood cells
100 m
Capillary
LM
Red blood cell
15 m
Figure 42.10c
• Capillaries have thin walls, the endothelium plus
its basal lamina, to facilitate the exchange of
materials
• Arteries and veins have an endothelium, smooth
muscle, and connective tissue
• Arteries have thicker walls than veins to
accommodate the high pressure of blood pumped
from the heart
• In the thinner-walled veins, blood flows back to the
heart mainly as a result of muscle action
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Blood Flow Velocity
• Physical laws governing movement of fluids
through pipes affect blood flow and blood pressure
• Velocity of blood flow is slowest in the capillary
beds, as a result of the high resistance and large
total cross-sectional area
• Blood flow in capillaries is necessarily slow for
exchange of materials
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Velocity
(cm/sec)
5,000
4,000
3,000
2,000
1,000
0
50
40
30
20
10
0
Pressure
(mm Hg)
Area (cm2)
Figure 42.11
120
100
80
60
40
20
0
Systolic
pressure
Diastolic
pressure
Blood Pressure
• Blood flows from areas of higher pressure to areas
of lower pressure
• Blood pressure is the pressure that blood exerts
against the wall of a vessel
• In rigid vessels blood pressure is maintained; less
rigid vessels deform and blood pressure is lost
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Changes in Blood Pressure During the
Cardiac Cycle
• Systolic pressure is the pressure in the arteries
during ventricular systole; it is the highest pressure
in the arteries
• Diastolic pressure is the pressure in the arteries
during diastole; it is lower than systolic pressure
• A pulse is the rhythmic bulging of artery walls with
each heartbeat
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Regulation of Blood Pressure
• Blood pressure is determined by cardiac output
and peripheral resistance due to constriction of
arterioles
• Vasoconstriction is the contraction of smooth
muscle in arteriole walls; it increases blood
pressure
• Vasodilation is the relaxation of smooth muscles
in the arterioles; it causes blood pressure to fall
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• Vasoconstriction and vasodilation help maintain
adequate blood flow as the body’s demands
change
• Nitric oxide is a major inducer of vasodilation
• The peptide endothelin is an important inducer of
vasoconstriction
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Blood Pressure and Gravity
• Blood pressure is generally measured for an artery
in the arm at the same height as the heart
• Blood pressure for a healthy 20-year-old at rest is
120 mm Hg at systole and 70 mm Hg at diastole
© 2011 Pearson Education, Inc.
Figure 42.12
Blood pressure reading: 120/70
1
3
2
120
120
70
Artery
closed
Sounds
audible in
stethoscope
Sounds
stop
• Fainting is caused by inadequate blood flow to the
head
• Animals with longer necks require a higher systolic
pressure to pump blood a greater distance against
gravity
• Blood is moved through veins by smooth muscle
contraction, skeletal muscle contraction, and
expansion of the vena cava with inhalation
• One-way valves in veins prevent backflow of blood
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Figure 42.13
Direction of blood flow
in vein (toward heart)
Valve (open)
Skeletal muscle
Valve (closed)
Capillary Function
• Blood flows through only 510% of the body’s
capillaries at a time
• Capillaries in major organs are usually filled to
capacity
• Blood supply varies in many other sites
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• Two mechanisms regulate distribution of blood in
capillary beds
– Contraction of the smooth muscle layer in the wall
of an arteriole constricts the vessel
– Precapillary sphincters control flow of blood
between arterioles and venules
• Blood flow is regulated by nerve impulses,
hormones, and other chemicals
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Figure 42.14
Precapillary
sphincters
Thoroughfare
channel
Arteriole
(a) Sphincters relaxed
Arteriole
(b) Sphincters contracted
Capillaries
Venule
Venule
• The exchange of substances between the blood
and interstitial fluid takes place across the thin
endothelial walls of the capillaries
• The difference between blood pressure and
osmotic pressure drives fluids out of capillaries at
the arteriole end and into capillaries at the venule
end
• Most blood proteins and all blood cells are too
large to pass through the endothelium
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Figure 42.15
INTERSTITIAL
FLUID
Net fluid movement out
Body cell
Blood
pressure
Osmotic
pressure
Arterial end
of capillary
Direction of blood flow
Venous end
of capillary
Fluid Return by the Lymphatic System
• The lymphatic system returns fluid that leaks out
from the capillary beds
• Fluid, called lymph, reenters the circulation
directly at the venous end of the capillary bed and
indirectly through the lymphatic system
• The lymphatic system drains into veins in the neck
• Valves in lymph vessels prevent the backflow of
fluid
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• Lymph nodes are organs that filter lymph and
play an important role in the body’s defense
• Edema is swelling caused by disruptions in the
flow of lymph
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Figure 42.16
Concept 42.4: Blood components contribute
to exchange, transport, and defense
• With open circulation, the fluid that is pumped
comes into direct contact with all cells
• The closed circulatory systems of vertebrates
contain blood, a specialized connective tissue
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Blood Composition and Function
• Blood consists of several kinds of cells suspended
in a liquid matrix called plasma
• The cellular elements occupy about 45% of the
volume of blood
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Figure 42.17
Cellular elements 45%
Plasma 55%
Constituent
Water
Solvent for
carrying other
substances
Ions (blood
electrolytes)
Sodium
Potassium
Calcium
Magnesium
Chloride
Bicarbonate
Osmotic balance,
pH buffering,
and regulation
of membrane
permeability
Plasma proteins
Albumin
Fibrinogen
Leukocytes (white blood cells)
Separated
blood
elements
5,000–10,000
Functions
Defense and
immunity
Lymphocytes
Basophils
Eosinophils
Neutrophils
Osmotic balance,
pH buffering
Monocytes
Platelets
250,000–400,000
Clotting
Immunoglobulins Defense
(antibodies)
Substances transported by blood
Nutrients
Waste products
Respiratory gases
Hormones
Number per L
(mm3) of blood
Cell type
Major functions
Erythrocytes (red blood cells)
5–6 million
Blood
clotting
Transport
of O2 and
some CO2
Figure 42.17a
Plasma 55%
Constituent
Major functions
Water
Solvent for
carrying other
substances
Ions (blood
electrolytes)
Sodium
Potassium
Calcium
Magnesium
Chloride
Bicarbonate
Osmotic balance,
pH buffering,
and regulation
of membrane
permeablity
Plasma proteins
Albumin
Fibrinogen
Immunoglobulins (antibodies)
Osmotic balance, pH buffering
Clotting
Defense
Substances transported by blood
Nutrients
Waste products
Respiratory gases
Hormones
Separated
blood
elements
Figure 42.17b
Cellular elements 45%
Number per L
(mm3) of blood
Cell type
Leukocytes (white blood cells)
Separated
blood
elements
5,000–10,000
Functions
Defense and
immunity
Lymphocytes
Basophils
Eosinophils
Neutrophils
Monocytes
Platelets
Erythrocytes (red blood cells)
250,000–400,000
5–6 million
Blood
clotting
Transport
of O2 and
some CO2
Plasma
• Blood plasma is about 90% water
• Among its solutes are inorganic salts in the form of
dissolved ions, sometimes called electrolytes
• Another important class of solutes is the plasma
proteins, which influence blood pH, osmotic
pressure, and viscosity
• Various plasma proteins function in lipid transport,
immunity, and blood clotting
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Cellular Elements
• Suspended in blood plasma are two types of cells
– Red blood cells (erythrocytes) transport oxygen O2
– White blood cells (leukocytes) function in defense
• Platelets, a third cellular element, are fragments of
cells that are involved in clotting
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Erythrocytes
• Red blood cells, or erythrocytes, are by far the
most numerous blood cells
• They contain hemoglobin, the iron-containing
protein that transports O2
• Each molecule of hemoglobin binds up to four
molecules of O2
• In mammals, mature erythrocytes lack nuclei and
mitochondria
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• Sickle-cell disease is caused by abnormal
hemoglobin proteins that form aggregates
• The aggregates can deform an erythrocyte into a
sickle shape
• Sickled cells can rupture or block blood vessels
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Leukocytes
• There are five major types of white blood cells, or
leukocytes: monocytes, neutrophils, basophils,
eosinophils, and lymphocytes
• They function in defense by phagocytizing bacteria
and debris or by producing antibodies
• They are found both in and outside of the
circulatory system
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Platelets
• Platelets are fragments of cells and function in
blood clotting
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Blood Clotting
• Coagulation is the formation of a solid clot from
liquid blood
• A cascade of complex reactions converts inactive
fibrinogen to fibrin, forming a clot
• A blood clot formed within a blood vessel is called
a thrombus and can block blood flow
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Figure 42.18
2
1
3
Collagen fibers
Platelet
plug
Platelet
Fibrin
clot
Clotting factors from:
Platelets
Damaged cells
Plasma (factors include calcium, vitamin K)
Enzymatic cascade
Prothrombin

Thrombin
Fibrinogen
Fibrin
Red blood cell
Fibrin clot formation
5 m
Figure 42.18a
3
2
1
Collagen fibers
Platelet
plug
Platelet
Fibrin
clot
Clotting factors from:
Platelets
Damaged cells
Plasma (factors include calcium, vitamin K)
Enzymatic cascade
Prothrombin

Thrombin
Fibrinogen
Fibrin
Fibrin clot
formation
Figure 42.18b
Fibrin
clot
Red blood cell
5 m
Stem Cells and the Replacement of Cellular
Elements
• The cellular elements of blood wear out and are
being replaced constantly
• Erythrocytes, leukocytes, and platelets all develop
from a common source of stem cells in the red
marrow of bones, especially ribs, vertebrae,
sternum, and pelvis
• The hormone erythropoietin (EPO) stimulates
erythrocyte production when O2 delivery is low
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Figure 42.19
Stem cells
(in bone marrow)
Myeloid
stem cells
Lymphoid
stem cells
B cells T cells
Erythrocytes
Neutrophils
Basophils
Lymphocytes
Monocytes
Platelets
Eosinophils
Cardiovascular Disease
• Cardiovascular diseases are disorders of the heart
and the blood vessels
• Cardiovascular diseases account for more than
half the deaths in the United States
• Cholesterol, a steroid, helps maintain membrane
fluidity
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• Low-density lipoprotein (LDL) delivers
cholesterol to cells for membrane production
• High-density lipoprotein (HDL) scavenges
cholesterol for return to the liver
• Risk for heart disease increases with a high LDL
to HDL ratio
• Inflammation is also a factor in cardiovascular
disease
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Atherosclerosis, Heart Attacks, and Stroke
• One type of cardiovascular disease,
atherosclerosis, is caused by the buildup of
plaque deposits within arteries
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Figure 42.20
Lumen of artery
Endothelium
Smooth
muscle
1
LDL
Foam cell
Macrophage
Plaque
2
Extracellular
matrix
Plaque rupture
4
3
Fibrous cap
Cholesterol
Smooth
muscle
cell
T lymphocyte
• A heart attack, or myocardial infarction, is the
death of cardiac muscle tissue resulting from
blockage of one or more coronary arteries
• Coronary arteries supply oxygen-rich blood to the
heart muscle
• A stroke is the death of nervous tissue in the
brain, usually resulting from rupture or blockage of
arteries in the head
• Angina pectoris is caused by partial blockage of
the coronary arteries and results in chest pains
© 2011 Pearson Education, Inc.
Risk Factors and Treatment of
Cardiovascular Disease
• A high LDL to HDL ratio increases the risk of
cardiovascular disease
• The proportion of LDL relative to HDL can be
decreased by exercise, not smoking, and avoiding
foods with trans fats
• Drugs called statins reduce LDL levels and risk of
heart attacks
© 2011 Pearson Education, Inc.
Figure 42.21
Average  105 mg/dL
30
20
10
0
0
50
100
150
200
250
300
Plasma LDL cholesterol (mg/dL)
Individuals with two functional copies of
PCSK9 gene (control group)
Percent of individuals
Percent of individuals
RESULTS
Average  63 mg/dL
30
20
10
0
0
50
100
150
200
250
300
Plasma LDL cholesterol (mg/dL)
Individuals with an inactivating mutation in
one copy of PCSK9 gene
• Inflammation plays a role in atherosclerosis and
thrombus formation
• Aspirin inhibits inflammation and reduces the risk
of heart attacks and stroke
• Hypertension, or high blood pressure, promotes
atherosclerosis and increases the risk of heart
attack and stroke
• Hypertension can be reduced by dietary changes,
exercise, and/or medication
© 2011 Pearson Education, Inc.
Concept 42.5: Gas exchange occurs across
specialized respiratory surfaces
• Gas exchange supplies O2 for cellular respiration
and disposes of CO2
© 2011 Pearson Education, Inc.
Partial Pressure Gradients in Gas Exchange
• A gas diffuses from a region of higher partial
pressure to a region of lower partial pressure
• Partial pressure is the pressure exerted by a
particular gas in a mixture of gases
• Gases diffuse down pressure gradients in the
lungs and other organs as a result of differences in
partial pressure
© 2011 Pearson Education, Inc.
Respiratory Media
• Animals can use air or water as a source of O2, or
respiratory medium
• In a given volume, there is less O2 available in
water than in air
• Obtaining O2 from water requires greater
efficiency than air breathing
© 2011 Pearson Education, Inc.
Respiratory Surfaces
• Animals require large, moist respiratory surfaces
for exchange of gases between their cells and the
respiratory medium, either air or water
• Gas exchange across respiratory surfaces takes
place by diffusion
• Respiratory surfaces vary by animal and can
include the outer surface, skin, gills, tracheae, and
lungs
© 2011 Pearson Education, Inc.
Gills in Aquatic Animals
• Gills are outfoldings of the body that create a large
surface area for gas exchange
© 2011 Pearson Education, Inc.
Figure 42.22
Coelom
Gills
Parapodium
(functions as gill)
(a) Marine worm
Gills
Tube foot
(b) Crayfish
(c) Sea star
Figure 42.22a
Parapodium (functions as gill)
(a) Marine worm
Figure 42.22b
Gills
(b) Crayfish
Figure 42.22c
Coelom
Gills
Tube foot
(c) Sea star
• Ventilation moves the respiratory medium over
the respiratory surface
• Aquatic animals move through water or move
water over their gills for ventilation
• Fish gills use a countercurrent exchange
system, where blood flows in the opposite
direction to water passing over the gills; blood is
always less saturated with O2 than the water it
meets
© 2011 Pearson Education, Inc.
Figure 42.23
O2-poor blood
Gill
arch
O2-rich blood
Lamella
Blood
vessels
Gill arch
Water
flow
Operculum
Water flow
Blood flow
Countercurrent exchange
PO (mm Hg) in water
2
150 120 90 60 30
Gill filaments
Net diffusion of O2
140 110 80 50 20
PO (mm Hg)
2
in blood
Figure 42.23a
Gill
arch
Blood
vessels
Gill arch
Water
flow
Operculum
Gill filaments
Figure 42.23b
O2-poor blood
O2-rich blood
Lamella
Water flow
Blood flow
Countercurrent exchange
PO (mm Hg) in water
2
150 120 90 60 30
Net diffusion of O2
140 110 80 50 20
PO (mm Hg)
2
in blood
Tracheal Systems in Insects
• The tracheal system of insects consists of tiny
branching tubes that penetrate the body
• The tracheal tubes supply O2 directly to body cells
• The respiratory and circulatory systems are
separate
• Larger insects must ventilate their tracheal system
to meet O2 demands
© 2011 Pearson Education, Inc.
Tracheoles Mitochondria
Muscle fiber
2.5 m
Figure 42.24
Tracheae
Air sacs
Body
cell
Air
sac
Tracheole
Trachea
External opening
Air
Figure 42.24a
Muscle fiber
2.5 m
Tracheoles Mitochondria
Lungs
• Lungs are an infolding of the body surface
• The circulatory system (open or closed) transports
gases between the lungs and the rest of the body
• The size and complexity of lungs correlate with an
animal’s metabolic rate
© 2011 Pearson Education, Inc.
Mammalian Respiratory Systems: A Closer
Look
• A system of branching ducts conveys air to the
lungs
• Air inhaled through the nostrils is warmed,
humidified, and sampled for odors
• The pharynx directs air to the lungs and food to
the stomach
• Swallowing tips the epiglottis over the glottis in the
pharynx to prevent food from entering the trachea
© 2011 Pearson Education, Inc.
Figure 42.25
Branch of
pulmonary vein
(oxygen-rich
blood)
Terminal
bronchiole
Branch of
pulmonary artery
(oxygen-poor
blood)
Nasal
cavity
Pharynx
Left
lung
Larynx
(Esophagus)
Alveoli
50 m
Trachea
Right lung
Capillaries
Bronchus
Bronchiole
Diaphragm
(Heart)
Dense capillary bed
enveloping alveoli (SEM)
Figure 42.25a
Nasal
cavity
Pharynx
Left
lung
Larynx
(Esophagus)
Trachea
Right lung
Bronchus
Bronchiole
Diaphragm
(Heart)
Figure 42.25b
Branch of
pulmonary vein
(oxygen-rich
blood)
Terminal
bronchiole
Branch of
pulmonary artery
(oxygen-poor
blood)
Alveoli
Capillaries
Figure 42.25c
50 m
Dense capillary bed
enveloping alveoli (SEM)
• Air passes through the pharynx, larynx, trachea,
bronchi, and bronchioles to the alveoli, where
gas exchange occurs
• Exhaled air passes over the vocal cords in the
larynx to create sounds
• Cilia and mucus line the epithelium of the air ducts
and move particles up to the pharynx
• This “mucus escalator” cleans the respiratory
system and allows particles to be swallowed into
the esophagus
© 2011 Pearson Education, Inc.
• Gas exchange takes place in alveoli, air sacs at
the tips of bronchioles
• Oxygen diffuses through the moist film of the
epithelium and into capillaries
• Carbon dioxide diffuses from the capillaries across
the epithelium and into the air space
© 2011 Pearson Education, Inc.
• Alveoli lack cilia and are susceptible to
contamination
• Secretions called surfactants coat the surface of
the alveoli
• Preterm babies lack surfactant and are vulnerable
to respiratory distress syndrome; treatment is
provided by artificial surfactants
© 2011 Pearson Education, Inc.
Figure 42.26
RDS deaths
Surface tension (dynes/cm)
RESULTS
Deaths from other causes
40
30
20
10
0
0
800
1,600
2,400
3,200
Body mass of infant (g)
4,000
Concept 42.6: Breathing ventilates the lungs
• The process that ventilates the lungs is breathing,
the alternate inhalation and exhalation of air
© 2011 Pearson Education, Inc.
How an Amphibian Breathes
• An amphibian such as a frog ventilates its lungs by
positive pressure breathing, which forces air
down the trachea
© 2011 Pearson Education, Inc.
How a Bird Breathes
• Birds have eight or nine air sacs that function as
bellows that keep air flowing through the lungs
• Air passes through the lungs in one direction only
• Every exhalation completely renews the air in the
lungs
© 2011 Pearson Education, Inc.
Figure 42.27
Anterior
air sacs
Posterior
air sacs
Lungs
Airflow
Air tubes
(parabronchi)
in lung
1 mm
Posterior
air sacs
Lungs
3
Anterior
air sacs
2
4
1
1 First inhalation
3 Second inhalation
2 First exhalation
4 Second exhalation
Figure 42.27a
Airflow
Air tubes
(parabronchi)
in lung
1 mm
How a Mammal Breathes
• Mammals ventilate their lungs by negative
pressure breathing, which pulls air into the lungs
• Lung volume increases as the rib muscles and
diaphragm contract
• The tidal volume is the volume of air inhaled with
each breath
© 2011 Pearson Education, Inc.
Figure 42.28
1
Rib cage
expands.
2
Air
inhaled.
Lung
Diaphragm
Rib cage gets
smaller.
Air
exhaled.
• The maximum tidal volume is the vital capacity
• After exhalation, a residual volume of air remains
in the lungs
© 2011 Pearson Education, Inc.
Control of Breathing in Humans
• In humans, the main breathing control centers
are in two regions of the brain, the medulla
oblongata and the pons
• The medulla regulates the rate and depth of
breathing in response to pH changes in the
cerebrospinal fluid
• The medulla adjusts breathing rate and depth to
match metabolic demands
• The pons regulates the tempo
© 2011 Pearson Education, Inc.
• Sensors in the aorta and carotid arteries monitor
O2 and CO2 concentrations in the blood
• These sensors exert secondary control over
breathing
© 2011 Pearson Education, Inc.
Figure 42.29
Homeostasis:
Blood pH of about 7.4
CO2 level
decreases.
Response:
Rib muscles
and diaphragm
increase rate
and depth of
ventilation.
Stimulus:
Rising level of
CO2 in tissues
lowers blood pH.
Carotid
arteries
Sensor/control center:
Cerebrospinal fluid
Medulla
oblongata
Aorta
Concept 42.7: Adaptations for gas exchange
include pigments that bind and transport
gases
• The metabolic demands of many organisms
require that the blood transport large quantities of
O2 and CO2
© 2011 Pearson Education, Inc.
Coordination of Circulation and Gas
Exchange
• Blood arriving in the lungs has a low partial
pressure of O2 and a high partial pressure of CO2
relative to air in the alveoli
• In the alveoli, O2 diffuses into the blood and CO2
diffuses into the air
• In tissue capillaries, partial pressure gradients
favor diffusion of O2 into the interstitial fluids and
CO2 into the blood
© 2011 Pearson Education, Inc.
Figure 42.30
Alveolar
epithelial
cells
2 Alveolar
spaces
CO2
O2
Alveolar
capillaries
7 Pulmonary
arteries
3 Pulmonary
veins
6 Systemic
veins
4 Systemic
arteries
Heart
CO2
Partial pressure (mm Hg)
1 Inhaled air
8 Exhaled air
160
O2
5 Body tissue
(a) The path of respiratory gases in the circulatory
system
2
Exhaled
air
120
80
40
0
1
Systemic
capillaries
PO
2
PCO
Inhaled
air
2
3
4
5
6
7
(b) Partial pressure of O2 and CO2 at different points in the
circulatory system numbered in (a)
8
Figure 42.30a
1 Inhaled air
8 Exhaled air
Alveolar
epithelial
cells
2 Alveolar
spaces
CO2
O2
Alveolar
capillaries
7 Pulmonary
arteries
3 Pulmonary
veins
6 Systemic
veins
4 Systemic
arteries
Heart
CO2
O2
Systemic
capillaries
5 Body tissue
(a) The path of respiratory gases in the circulatory
system
Partial pressure (mm Hg)
Figure 42.30b
160
PO
2
PCO
Inhaled
air
2
Exhaled
air
120
80
40
0
1
2
3
4
5
6
7
8
(b) Partial pressure of O2 and CO2 at different points in the
circulatory system numbered in (a)
Respiratory Pigments
• Respiratory pigments, proteins that transport
oxygen, greatly increase the amount of oxygen
that blood can carry
• Arthropods and many molluscs have hemocyanin
with copper as the oxygen-binding component
• Most vertebrates and some invertebrates use
hemoglobin
• In vertebrates, hemoglobin is contained within
erythrocytes
© 2011 Pearson Education, Inc.
Hemoglobin
• A single hemoglobin molecule can carry four
molecules of O2, one molecule for each ironcontaining heme group
• The hemoglobin dissociation curve shows that a
small change in the partial pressure of oxygen can
result in a large change in delivery of O2
• CO2 produced during cellular respiration lowers
blood pH and decreases the affinity of hemoglobin
for O2; this is called the Bohr shift
© 2011 Pearson Education, Inc.
Figure 42.UN01
Iron
Heme
Hemoglobin
100
O2 unloaded
to tissues
at rest
80
O2 unloaded
to tissues
during exercise
60
40
20
0
O2 saturation of hemoglobin (%)
O2 saturation of hemoglobin (%)
Figure 42.31
100
pH 7.4
80
pH 7.2
Hemoglobin
retains less
O2 at lower pH
(higher CO2
concentration)
60
40
20
0
0
20
40
60
Tissues during Tissues
at rest
exercise
PO2 (mm Hg)
80
100
Lungs
(a) PO2 and hemoglobin dissociation at pH 7.4
0
20
40
60
80
PO2 (mm Hg)
(b) pH and hemoglobin dissociation
100
O2 saturation of hemoglobin (%)
Figure 42.31a
100
O2 unloaded
to tissues
at rest
80
O2 unloaded
to tissues
during exercise
60
40
20
0
0
20
40
60
Tissues during Tissues
at rest
exercise
PO2 (mm Hg)
80
100
Lungs
(a) PO2 and hemoglobin dissociation at pH 7.4
O2 saturation of hemoglobin (%)
Figure 42.31b
100
pH 7.4
80
pH 7.2
Hemoglobin
retains less
O2 at lower pH
(higher CO2
concentration)
60
40
20
0
0
20
40
60
80
PO2 (mm Hg)
(b) pH and hemoglobin dissociation
100
Carbon Dioxide Transport
• Hemoglobin also helps transport CO2 and assists
in buffering the blood
• CO2 from respiring cells diffuses into the blood
and is transported in blood plasma, bound to
hemoglobin, or as bicarbonate ions (HCO3–)
Animation: O2 from Blood to Tissues
Animation: CO2 from Tissues to Blood
Animation: CO2 from Blood to Lungs
Animation: O2 from Lungs to Blood
© 2011 Pearson Education, Inc.
Figure 42.32
Body tissue
CO2 produced
CO2 transport
from tissues
Interstitial
CO2
fluid
Plasma
within capillary CO2
H2O
Red
blood
cell
Capillary
wall
CO2
H2CO3
Hb
Carbonic
acid
HCO3 
Bicarbonate
HCO3
H+
To lungs
CO2 transport
to lungs
HCO3
HCO3 
H2CO3
Hemoglobin (Hb)
picks up
CO2 and H+.
H+
Hb
Hemoglobin
releases
CO2 and H+.
H2O
CO2
CO2
CO2
CO2
Alveolar space in lung
Figure 42.32a
Body tissue
CO2 produced
CO2 transport
from tissues
Interstitial
CO2
fluid
Plasma
CO2
within capillary
Capillary
wall
CO2
H2O
Red
blood
cell
H2CO3
Hb
Carbonic
acid
HCO3 
Bicarbonate
Hemoglobin (Hb)
picks up
CO2 and H+.
H+
HCO3
To lungs
Figure 42.32b
To lungs
CO2 transport
to lungs
HCO3
HCO3 
H2CO3
H+
Hb
Hemoglobin
releases
CO2 and H+.
H2O
CO2
CO2
CO2
CO2
Alveolar space in lung
Respiratory Adaptations of Diving Mammals
• Diving mammals have evolutionary adaptations
that allow them to perform extraordinary feats
– For example, Weddell seals in Antarctica can
remain underwater for 20 minutes to an hour
– For example, elephant seals can dive to 1,500 m
and remain underwater for 2 hours
• These animals have a high blood to body volume
ratio
© 2011 Pearson Education, Inc.
• Deep-diving air breathers stockpile O2 and deplete
it slowly
• Diving mammals can store oxygen in their
muscles in myoglobin proteins
• Diving mammals also conserve oxygen by
– Changing their buoyancy to glide passively
– Decreasing blood supply to muscles
– Deriving ATP in muscles from fermentation once
oxygen is depleted
© 2011 Pearson Education, Inc.
Figure 42.UN02
Inhaled air
Exhaled air
Alveolar
epithelial
cells
Alveolar
spaces
CO2
O2
Alveolar
capillaries
Pulmonary
arteries
Pulmonary
veins
Systemic
veins
Systemic
arteries
Heart
CO2
O2
Systemic
capillaries
Body tissue
O2 saturation of
hemoglobin (%)
Figure 42.UN03
100
80
60
Fetus
Mother
40
20
0
0 20 40 60 80 100
PO2 (mm Hg)
Figure 42.UN04