Download Chapter 42 - Circulation and Gas Exchange

Figure 42.1
CAMPBELL
BIOLOGY
Trading Places
TENTH
EDITION
Reece • Urry • Cain • Wasserman • Minorsky • Jackson
42
Circulation and
Gas Exchange
!  Every organism must exchange materials with its
environment
!  For most cells of multicellular organisms, direct
exchange with the environment is not possible
!  Exchanges ultimately occur at the cellular level by
crossing the plasma membrane
!  Gills are an example of a specialized exchange
system in animals
!  O2 diffuses from the water into blood vessels
!  In unicellular organisms, these exchanges occur
directly with the environment
!  CO2 diffuses from blood into the water
!  Internal transport and gas exchange are
functionally related in most animals
Lecture Presentation by
Nicole Tunbridge and
Kathleen Fitzpatrick
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Figure 42.2
Concept 42.1: Circulatory systems link
exchange surfaces with cells throughout
the body
Gastrovascular Cavities
!  Some animals lack a circulatory system
!  In small or thin animals, cells can exchange
materials directly with the surrounding medium
!  Small molecules can move between cells and
their surroundings by diffusion
!  In most animals, cells exchange materials with the
environment via a fluid-filled circulatory system
!  Diffusion is only efficient over small distances
because the time it takes to diffuse is proportional
to the square of the distance
Mouth
!  Some cnidarians have elaborate gastrovascular
cavities
!  A gastrovascular cavity functions in both
digestion and distribution of substances
throughout the body
Radial canals
Circular canal
!  The body wall that encloses the gastrovascular
cavity is only two cells thick
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Figure 42.2a
(a) The moon jelly Aurelia, a cnidarian
2.5 cm
Mouth
Gastrovascular 1 mm
Pharynx
cavity
(b) The planarian Dugesia, a flatworm
!  Flatworms have a gastrovascular cavity and a flat
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body that minimizes diffusion distances
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Figure 42.2b
Open and Closed Circulatory Systems
Mouth
!  A circulatory system has
!  In insects, other arthropods, and some molluscs,
circulatory fluid called hemolymph bathes the
organs directly in an open circulatory system
!  A circulatory fluid
!  A set of interconnecting vessels
Gastrovascular 1 mm
Pharynx
cavity
(b) The planarian Dugesia, a flatworm
Radial canals
Circular canal
!  The circulatory system connects the fluid that
surrounds cells with the organs that exchange
gases, absorb nutrients, and dispose of wastes
2.5 cm
(a) The moon jelly Aurelia, a cnidarian
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Figure 42.3
Figure 42.3a
Tubular heart
!  Humans and other vertebrates have a closed
circulatory system called the cardiovascular
system
Heart
Interstitial fluid
Blood
Hemolymph in sinuses
Blood
Auxiliary
hearts
Pores
Dorsal
vessel
(main
heart)
Ventral vessels
Tubular heart
!  Blood flow is one way in these vessels
Auxiliary
hearts
Ventral vessels
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!  The three main types of blood vessels are arteries,
veins, and capillaries
Small
branch vessels
in each organ
Small
branch vessels
in each organ
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Organization of Vertebrate Circulatory Systems
(b) A closed circulatory system
Heart
Dorsal
vessel
(main
heart)
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Heart
Interstitial fluid
Pores
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Figure 42.3b
(b) A closed circulatory system
Heart
Hemolymph in sinuses
!  Circulatory systems can be open or closed and
vary in the number of circuits in the body
!  Annelids, cephalopods, and vertebrates have
closed circulatory systems
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(a) An open circulatory system
(a) An open circulatory system
!  In a closed circulatory system, blood is
confined to vessels and is distinct from the
interstitial fluid
!  A muscular pump, the heart
Mouth
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Figure 42.4a
(a) Single circulation:
fish
Single Circulation
Gill
capillaries
!  Arteries branch into arterioles and carry blood
away from the heart to capillaries
!  Arteries and veins are distinguished by the
direction of blood flow, not by O2 content
!  Bony fishes, rays, and sharks have single
circulation with a two-chambered heart
!  Networks of capillaries called capillary beds are
the sites of chemical exchange between the blood
and interstitial fluid
!  Vertebrate hearts contain two or more chambers
!  In single circulation, blood leaving the heart
passes through two capillary beds before returning
!  Blood enters through an atrium and is pumped out
through a ventricle
Artery
Heart:
Atrium (A)
Ventricle (V)
!  Venules converge into veins and return blood
from capillaries to the heart
Vein
Body
capillaries
Key
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Figure 42.4b
Double Circulation
!  Oxygen-poor and oxygen-rich blood are pumped
separately from the right and left sides of the heart
Figure 42.4c
(b) Double circulation:
amphibian
!  In reptiles and mammals, oxygen-poor blood flows
through the pulmonary circuit to pick up oxygen
through the lungs
(c) Double circulation:
mammal
Pulmonary circuit
Lung
and skin
capillaries
Atrium
(A)
!  In amphibians, oxygen-poor blood flows through a
pulmocutaneous circuit to pick up oxygen through
the lungs and skin
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Atrium
(A)
A
A
V
!  Oxygen-rich blood delivers oxygen through the
systemic circuit
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Lung
capillaries
Right
Left
Ventricle (V)
V
Left
Right
Systemic
capillaries
!  Double circulation maintains higher blood pressure
in the organs than does single circulation
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Pulmocutaneous circuit
!  Amphibians, reptiles, and mammals have double
circulation
Oxygen-rich blood
Oxygen-poor blood
Key
Systemic circuit
Oxygen-rich blood
Oxygen-poor blood
Systemic
capillaries
Systemic circuit
Key
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Oxygen-rich blood
Oxygen-poor blood
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Evolutionary Variation in Double Circulation
!  Some vertebrates with double circulation are
intermittent breathers
!  Frogs and other amphibians have a threechambered heart: two atria and one ventricle
!  For example, amphibians and many reptiles may
pass long periods without gas exchange, or relying
on gas exchange from another tissue, usually
the skin
!  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
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!  Turtles, snakes, and lizards have a threechambered heart: two atria and one ventricle,
partially divided by an incomplete septum
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Concept 42.2: Coordinated cycles of heart
contraction drive double circulation in
mammals
Mammalian Circulation
!  The left side of the heart pumps and receives only
oxygen-rich blood, while the right side receives
and pumps only oxygen-poor blood
!  In alligators, caimans, and other crocodilians a
septum divides the ventricles but pulmonary and
systemic circuits connect where arteries exit
the heart
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!  Mammals and birds have a four-chambered heart
with two atria and two ventricles
!  Mammals and birds are endotherms and require
more O2 than ectotherms
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Figure 42.5
!  The mammalian cardiovascular system meets the
body s continuous demand for O2
!  In the lungs, the blood loads O2 and unloads CO2
!  Oxygen-rich blood from the lungs enters the heart
at the left atrium via the pulmonary veins
!  It is pumped through the aorta to the body tissues
by the left ventricle
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Capillaries
of right lung
!  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
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Pulmonary
artery
Aorta
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2
3
4
11
Pulmonary
vein
Right atrium
Right ventricle
Capillaries
of left lung
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3
1
Pulmonary
vein
Left atrium
Left ventricle
5
10
Aorta
Inferior
vena cava
8
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Capillaries of
head and
forelimbs
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Pulmonary
artery
!  The aorta provides blood to the heart through the
coronary arteries
!  Blood begins its flow with the right ventricle
pumping blood to the lungs via the pulmonary
arteries
Superior
vena cava
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Capillaries of
abdominal organs
and hind limbs
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Figure 42.6
Animation: Path of Blood Flow in Mammals
The Mammalian Heart: A Closer Look
Aorta
Pulmonary artery
Pulmonary
artery
!  A closer look at the mammalian heart provides
a better understanding of double circulation
Right
atrium
!  The two atria have relatively thin walls and serve
as collection chambers for blood returning to
the heart
!  The ventricles have thicker walls and contract
much more forcefully
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Semilunar
valve
Atrioventricular
(AV) valve
Atrioventricular
(AV) valve
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Figure 42.7-3
2 Atrial systole and
ventricular diastole
1 Atrial and
ventricular diastole
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Figure 42.7-2
1 Atrial and
ventricular diastole
!  The relaxation, or filling, phase is called diastole
Left
ventricle
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Figure 42.7-1
!  The contraction, or pumping, phase is called
systole
Semilunar
valve
Right
ventricle
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!  The heart contracts and relaxes in a rhythmic
cycle called the cardiac cycle
Left
atrium
2 Atrial systole and
ventricular diastole
!  The heart rate, also called the pulse, is the
number of beats per minute
1 Atrial and
ventricular diastole
!  The stroke volume is the amount of blood
pumped in a single contraction
0.1
sec
0.4
sec
0.1
sec
0.4
sec
0.4
sec
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3 Ventricular systole
and atrial diastole
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!  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
0.3 sec
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Figure 42.8-1
Maintaining the Heart s Rhythmic Beat
!  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
!  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
!  Some cardiac muscle cells are autorhythmic,
meaning they contract without any signal from
the nervous system
!  Backflow of blood through a defective valve
causes a heart murmur
!  The sinoatrial (SA) node, or pacemaker, sets
the rate and timing at which cardiac muscle
cells contract
1 Signals (yellow)
from SA node
spread through
atria.
SA node
(pacemaker)
!  Impulses that travel during the cardiac cycle
can be recorded as an electrocardiogram
(ECG or EKG)
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Figure 42.8-2
1 Signals (yellow)
from SA node
spread through
atria.
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1 Signals (yellow)
from SA node
spread through
atria.
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Figure 42.8-3
2 Signals are
delayed at AV
node.
ECG
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Figure 42.8-4
2 Signals are
delayed at AV
node.
3 Bundle branches
pass signals to
heart apex.
1 Signals (yellow)
from SA node
spread through
atria.
2 Signals are
delayed at AV
node.
3 Bundle branches
pass signals to
heart apex.
4 Signals
spread
throughout
ventricles.
!  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
SA node
(pacemaker)
AV
node
SA node
(pacemaker)
ECG
Bundle
branches
SA node
(pacemaker)
Heart
apex
ECG
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AV
node
Bundle
branches
Heart
apex
Purkinje
fibers
ECG
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AV
node
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Concept 42.3: Patterns of blood pressure and
flow reflect the structure and arrangement of
blood vessels
!  The pacemaker is regulated by two portions of
the nervous system: the sympathetic and
parasympathetic divisions
!  The sympathetic division speeds up the pacemaker
Blood Vessel Structure and Function
!  A vessel s cavity is called the central lumen
!  The physical principles that govern movement of
water in plumbing systems apply to the functioning
of blood vessels
!  The parasympathetic division slows down the
pacemaker
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Artery
!  Arteries and veins have an endothelium, smooth
muscle, and connective tissue
!  The endothelium is smooth and minimizes
resistance
!  Arteries have thicker walls than veins to
accommodate the high pressure of blood pumped
from the heart
!  Capillaries are only slightly wider than a red
blood cell
!  The pacemaker is also regulated by hormones
and temperature
Figure 42.9
!  Capillaries have thin walls, the endothelium plus
its basal lamina, to facilitate the exchange of
materials
!  The epithelial layer that lines blood vessels is
called the endothelium
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Figure 42.9a
Vein
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!  In the thinner-walled veins, blood flows back to the
heart mainly as a result of muscle action
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Figure 42.9b
Figure 42.9c
Valve
Endothelium
Smooth
muscle
Connective
Capillary
tissue
Endothelium
Smooth
muscle
Connective
tissue
Artery
Endothelium
Smooth
muscle
Connective
tissue
Smooth
muscle
Connective
Capillary
tissue
Artery
Vein
Red blood cell
Vein
LM
Vein
Artery
Capillary
Red blood cells 100 µm
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Venae
cavae
Veins
Venules
Arterioles
Aorta
Diastolic
pressure
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!  Blood pressure is the pressure that blood exerts
in all directions, including against the walls of
blood vessels
Systolic
pressure
!  The recoil of elastic arterial walls plays a role in
maintaining blood pressure
Diastolic
pressure
Venae
cavae
120
100
80
60
40
20
0
!  Blood flows from areas of higher pressure to areas
of lower pressure
Veins
50
40
30
20
10
0
Blood Pressure
Venules
Area (cm2)
Velocity
(cm/sec)
Systolic
pressure
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Changes in Blood Pressure During the
Cardiac Cycle
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!  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
!  Nitric oxide is a major inducer of vasodilation
!  Blood pressure is generally measured for an artery
in the arm at the same height as the heart
!  The peptide endothelin is a strong inducer of
vasoconstriction
!  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
!  Blood pressure for a healthy 20-year-old human at
rest is about 120 mm Hg at systole and 70 mm Hg
at diastole
!  Vasoconstriction and vasodilation are often
coupled to changes in cardiac output that affect
blood pressure
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Blood Pressure and Gravity
!  Homeostatic mechanisms regulate arterial blood
pressure by altering the diameter of arterioles
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!  The resistance to blood flow in the narrow
diameters of tiny capillaries and arterioles
dissipates much of the pressure
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Regulation of Blood Pressure
!  Systolic pressure is the pressure in the arteries
during ventricular systole; it is the highest pressure
in the arteries
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120
100
80
60
40
20
0
Capillaries
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50
40
30
20
10
0
Arteries
!  Blood flow in capillaries is necessarily slow for
exchange of materials
Velocity
(cm/sec)
!  Velocity of blood flow is slowest in the capillary
beds, as a result of the high resistance and large
total cross-sectional area
5,000
4,000
3,000
2,000
1,000
0
Pressure
(mm Hg)
Area (cm2)
!  Physical laws governing movement of fluids
through pipes affect blood flow and blood pressure
5,000
4,000
3,000
2,000
1,000
0
Capillaries
Figure 42.10a
Arteries
Figure 42.10
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Arterioles
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Blood Flow Velocity
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Aorta
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Pressure
(mm Hg)
Capillary
Venule
Arteriole
15 µm
Red blood cell
Venule
LM
Arteriole
15 µm
Endothelium
Valve
Basal lamina
LM
LM
Basal lamina
Red blood cells 100 µm
!  Gravity has a significant effect on blood pressure
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Figure 42.11
Figure 42.12
Capillary Function
Pressure in cuff
greater than
120 mm Hg
Cuff
inflated
with air
1
Artery
closed
Pressure in cuff
drops below
120 mm Hg
120
Pressure in
cuff below
70 mm Hg
120
70
2
Sounds
audible in
stethoscope
3
Direction of blood flow
in vein (toward heart)
!  Fainting is caused by inadequate blood flow to
the head
Valve (open)
!  Blood flows through only 5–10% of the body s
capillaries at any given time
!  Animals with long necks require a very high
systolic pressure to pump blood a great distance
against gravity
Skeletal muscle
!  Capillaries in major organs are usually filled
to capacity
!  Blood supply varies in many other sites
!  Blood is moved through veins by smooth muscle
contraction, skeletal muscle contraction, and
expansion of the vena cava with inhalation
Sounds
stop
Valve (closed)
!  One-way valves in veins prevent backflow of blood
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Figure 42.13
Precapillary sphincters
Figure 42.14
!  The exchange of substances between the blood
and interstitial fluid takes place across the thin
endothelial walls of the capillaries
Capillaries
Venule
Arteriole
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Thoroughfare
channel
!  Two mechanisms regulate distribution of blood in
capillary beds
!  Constriction or dilation of arterioles that supply
capillary beds
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INTERSTITIAL
FLUID
!  Precapillary sphincters that control flow of blood
between arterioles and venules
!  Blood flow is regulated by nerve impulses,
hormones, and other chemicals
Osmotic
pressure
!  Most blood proteins and all blood cells are too
large to pass through the endothelium
Arteriole
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Body cell
Blood
pressure
!  The difference between blood pressure and
osmotic pressure drives fluids out of capillaries
at the arteriole end and into capillaries at the
venule end
(a) Sphincters relaxed
Net fluid movement out
Arterial end
of capillary
Direction of blood flow
Venous end
of capillary
Venule
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(b) Sphincters contracted
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Figure 42.15
Concept 42.4: Blood components function in
exchange, transport, and defense
Fluid Return by the Lymphatic System
!  The lymphatic system returns fluid that leaks
out from the capillary beds
!  Edema is swelling caused by disruptions in the
flow of lymph
!  Fluid lost by capillaries is called lymph
!  Lymph nodes are organs that filter lymph and
play an important role in the body s defense
!  The lymphatic system drains into veins in the neck
!  The closed circulatory systems of vertebrates
contain a more highly specialized fluid called blood
!  When the body is fighting an infection, lymph
nodes become swollen and tender
!  Valves in lymph vessels prevent the backflow
of fluid
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Figure 42.16
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Figure 42.16a
Figure 42.16b
Blood Composition and Function
Plasma 55%
Constituent
Plasma 55%
Constituent
!  Blood in vertebrates is a connective tissue
consisting of several kinds of cells suspended
in a liquid matrix called plasma
!  The cellular elements occupy about 45% of the
volume of blood
Major functions
Water
Solvent
Ions (blood
electrolytes)
Sodium
Potassium
Calcium
Magnesium
Chloride
Bicarbonate
Osmotic balance,
pH buffering,
and regulation
of membrane
permeability
Plasma proteins
Albumin
Cellular elements 45%
Lipid transport
Fibrinogen
Clotting
5,000–10,000
Leukocytes
(white blood cells)
Osmotic balance,
pH buffering
Apolipoproteins
Number per
µL (mm3) of blood
Cell type
Separated
blood
elements
Functions
Defense and
immunity
Eosinophils
Neutrophils
Platelets
Monocytes
250,000–400,000
Blood clotting
Substances transported by blood
Nutrients (such as glucose,
fatty acids, vitamins)
Waste products of metabolism
Respiratory gases (O2 and CO2)
Hormones
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Water
Solvent
Ions (blood
electrolytes)
Osmotic balance,
pH buffering,
and regulation
of membrane
permeability
Sodium, Potassium
Calcium, Magnesium
Chloride, Bicarbonate
Erythrocytes
(red blood cells)
5,000,000–6,000,000 Transport of O2
and some CO2
Plasma proteins
Albumin
Immunoglobulins
(antibodies)
Apolipoproteins
Fibrinogen
Leukocytes
(white blood cells)
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5,000–10,000
Functions
Defense and
immunity
Lymphocytes
Basophils
Osmotic balance, pH buffering
Defense
Eosinophils
Lipid transport
Clotting
Nutrients (such as glucose, fatty acids, vitamins)
Waste products of metabolism
Respiratory gases (O2 and CO2)
Hormones
Number per
µL (mm3) of blood
Cell type
Neutrophils
Platelets
Substances transported by blood
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Cellular elements 45%
Major functions
Lymphocytes
Basophils
Immunoglobulins Defense
(antibodies)
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!  With open circulation, the fluid is continuous with
the fluid surrounding all body cells
Lymph nodes
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Erythrocytes
(red blood cells)
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Monocytes
250,000–400,000
5,000,000–6,000,000
Blood clotting
Transport of O2
and some CO2 80
Video: Leukocyte Adhesion and Rolling
Plasma
Cellular Elements
!  Plasma contains inorganic salts as dissolved
ions, sometimes called electrolytes
!  Suspended in blood plasma are two types of cells
!  Red blood cells (erythrocytes) transport O2
!  Plasma proteins influence blood pH and help
maintain osmotic balance between blood and
interstitial fluid
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!  Plasma is similar in composition to interstitial
fluid, but plasma has a much higher protein
concentration
!  Red blood cells, or erythrocytes, are the most
numerous blood cells
!  White blood cells (leukocytes) function in defense
!  They contain hemoglobin, the iron-containing
protein that transports O2
!  Platelets are fragments of cells that are involved
in clotting
!  Particular plasma proteins function in lipid
transport, immunity, and blood clotting
Erythrocytes
!  Each molecule of hemoglobin binds up to four
molecules of O2
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!  In mammals, mature erythrocytes lack nuclei
and mitochondria
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Stem Cells and the Replacement of Cellular
Elements
!  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
Leukocytes
Platelets
!  There are five major types of white blood cells, or
leukocytes: monocytes, neutrophils, basophils,
eosinophils, and lymphocytes
!  Platelets are fragments of cells and function in
blood clotting
!  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
!  They function in defense either by phagocytizing
bacteria and debris or by mounting immune
responses against foreign substances
!  The hormone erythropoietin (EPO) stimulates
erythrocyte production when O2 delivery is low
!  Physicians can use recombinant EPO to treat
people with conditions such as anemia
!  They are found both in and outside of the
circulatory system
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Figure 42.17
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Figure 42.18
Figure 42.18a
Blood Clotting
Stem cells
(in bone marrow)
1
2
3
!  Coagulation is the formation of a solid clot from
liquid blood
Myeloid
stem cells
Lymphoid
stem cells
1
B cells T cells
Erythrocytes
Lymphocytes
!  A blood clot formed within a blood vessel is called
a thrombus and can block blood flow
Neutrophils
2
3
Basophils
Collagen fibers
Platelet
plug
Platelet
Clotting factors from:
Platelets
Damaged cells
Plasma (factors include calcium, vitamin K)
Fibrin clot
Red blood cells caught
in threads of fibrin
5 µm
Clotting factors from:
Platelets
Damaged cells
Plasma (factors include calcium, vitamin K)
Fibrin clot
formation
Monocytes
Platelets
89
Prothrombin
Thrombin
Fibrinogen
Fibrin
90
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Fibrin clot
formation
Thrombin
Fibrinogen
Eosinophils
Fibrin clot
Enzymatic cascade
Enzymatic cascade
Prothrombin
Platelet
plug
Collagen fibers
Platelet
!  A cascade of complex reactions converts inactive
fibrinogen to fibrin, forming a clot
Fibrin
91
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92
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Figure 42.18b
Cardiovascular Disease
Atherosclerosis, Heart Attacks, and Stroke
!  Cardiovascular diseases are disorders of the heart
and the blood vessels
!  These diseases range in seriousness from minor
disturbances of vein or heart function to lifethreatening disruptions of blood flow to the heart
or brain
!  One type of cardiovascular disease,
atherosclerosis, is caused by the buildup of
fatty deposits (plaque) within arteries
!  Low-density lipoprotein (LDL) delivers
cholesterol to cells for membrane production
!  High-density lipoprotein (HDL) scavenges
excess cholesterol for return to the liver
!  Cholesterol is a key player in the development
of atherosclerosis
!  Risk for heart disease increases with a high
LDL to HDL ratio
!  Inflammation is also a factor in cardiovascular
disease
Red blood cells caught
in threads of fibrin
5 µm
93
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94
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95
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96
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Figure 42.19
Figure 42.20
Risk Factors and Treatment of
Cardiovascular Disease
!  A heart attack, or myocardial infarction, is the
damage or death of cardiac muscle tissue
resulting from blockage of one or more coronary
arteries
Endothelium
Lumen
1 A stent and a balloon
are inserted into an
obstructed artery.
Plaque
3 The balloon is removed,
leaving the stent in
place.
!  Angina pectoris is chest pain caused by partial
blockage of the coronary arteries
97
!  A high LDL/HDL ratio increases the risk of
cardiovascular disease
Stent
around
balloon
!  The proportion of LDL relative to HDL can be
decreased by exercise and by avoiding smoking
and foods with trans fats
Increased
blood
flow
98
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Plaque
2 Inflating the balloon
expands the stent,
widening the artery.
!  A stroke is the death of nervous tissue in the
brain, usually resulting from rupture or blockage
of arteries in the head
Thrombus
Artery
!  Drugs called statins reduce LDL levels and risk
of heart attacks
99
100
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Table 42.1
Concept 42.5: Gas exchange occurs across
specialized respiratory surfaces
!  Inflammation plays a role in atherosclerosis and
thrombus formation
!  Aspirin inhibits inflammation and reduces the risk
of heart attacks and stroke
Partial Pressure Gradients in Gas Exchange
!  Gas exchange supplies O2 for cellular respiration
and disposes of CO2
!  Hypertension, or high blood pressure, also
contributes to heart attack and stroke, as well as
other health problems
!  Partial pressure is the pressure exerted by a
particular gas in a mixture of gases
!  Partial pressures also apply to gases dissolved
in liquids such as water
!  Gases undergo net diffusion from a region of
higher partial pressure to a region of lower
partial pressure
!  Hypertension can be controlled by dietary
changes, exercise, and/or medication
101
102
103
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Respiratory Media
Respiratory Surfaces
Gills in Aquatic Animals
!  Animals can use air or water as the O2 source, 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
!  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
!  Ventilation moves the respiratory medium over
the respiratory surface
!  Ventilation moves the respiratory medium over
the respiratory surface
!  Aquatic animals move through water or move
water over their gills for ventilation
106
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Figure 42.21
!  Gills are outfoldings of the body that create a large
surface area for gas exchange
!  Aquatic animals move through water or move
water over their gills for ventilation
!  Respiratory surfaces vary by animal and can
include the skin, gills, tracheae, and lungs
105
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104
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107
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Figure 42.21a
108
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Figure 42.21b
Figure 42.21c
Coelom
Gills
Parapodium
(functions as gill)
(a) Marine worm
Gills
Tube foot
(c) Sea star
(c) Sea star
109
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(b) Crayfish
(a) Marine worm
(b) Crayfish
110
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111
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112
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Figure 42.22
Figure 42.22a
O2-poor blood
Gill
arch
!  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
Figure 42.22b
O2-rich blood
Blood
vessels
Blood
vessels
Gill arch
Water
flow
Gill arch
Lamella
Operculum
Water flow
!  In fish gills, more than 80% of the O2 dissolved in
the water is removed as water passes over the
respiratory surface
Water
flow
Blood flow
Lamella
Operculum
Water flow
Countercurrent exchange
PO (mm Hg) in water
150 120 90 60 30
2
150 120 90 60 30
140 110 80 50 20
Gill filaments
PO 2 (mm Hg)
in blood
113
Net diffusion
of O2
114
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Figure 42.23
115
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Tracheoles Mitochondria
Tracheal Systems in Insects
!  Lungs are an infolding of the body surface
Tracheoles Mitochondria Muscle fiber
!  The circulatory system (open or closed) transports
gases between the lungs and the rest of the body
2.5 µm
Air sacs
!  The size and complexity of lungs correlate with an
animal s metabolic rate
Body
cell
Air
sac
2.5 µm
Tracheae
!  Larger insects must ventilate their tracheal system
to meet O2 demands
116
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Lungs
!  The tracheal system of insects consists of a
network of branching tubes throughout the body
!  The respiratory and circulatory systems are
separate
140 110 80 50 20
PO 2 (mm Hg)
in blood
Figure 42.23a
Muscle fiber
!  The tracheal tubes supply O2 directly to body cells
Blood flow
Countercurrent exchange
PO 2 (mm Hg) in water
Gill filaments
Net diffusion of O2
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O2-poor blood
O2-rich blood
Gill
arch
Tracheole
Trachea
117
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External opening
Air
118
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119
120
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Figure 42.24
Mammalian Respiratory Systems: A Closer Look
!  A system of branching ducts conveys air to
the lungs
!  Air inhaled through the nostrils is filtered, warmed,
humidified, and sampled for odors
!  The pharynx directs air to the lungs and food to
the stomach
!  Swallowing moves the larynx upward and tips the
epiglottis over the glottis in the pharynx to prevent
food from entering the trachea
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!  Air passes through the pharynx, larynx, trachea,
bronchi, and bronchioles to the alveoli, where
gas exchange occurs
!  Oxygen diffuses through the moist film of the
epithelium and into capillaries
!  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
Figure 42.24a
Left lung
(Esophagus)
Alveoli
50 µm
Trachea
Right lung
Capillaries
Bronchus
Bronchiole
Diaphragm
(Heart)
Dense capillary bed
enveloping alveoli (SEM)
123
124
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Figure 42.24c
Branch of
pulmonary vein
(oxygen-rich
blood)
Terminal
bronchiole
Nasal
cavity
Pharynx
Larynx
Left lung
(Esophagus)
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Figure 42.24b
Nasal
cavity
Pharynx
Larynx
!  Carbon dioxide diffuses from the capillaries across
the epithelium and into the air space
!  This mucus escalator cleans the respiratory
system and allows particles to be swallowed into
the esophagus
122
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Branch of
pulmonary artery
(oxygen-poor
blood)
Branch of
pulmonary vein
(oxygen-rich
blood)
Terminal
bronchiole
!  Gas exchange takes place in alveoli, air sacs at
the tips of bronchioles
Trachea
Right lung
Branch of
pulmonary artery
(oxygen-poor
blood)
!  Alveoli lack cilia and are susceptible to
contamination
50 µm
!  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
Alveoli
Bronchus
Dense capillary bed
enveloping alveoli (SEM)
Bronchiole
Capillaries
Diaphragm
(Heart)
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125
126
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127
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128
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Figure 42.25
Concept 42.6: Breathing ventilates the lungs
Surface tension
(dynes/cm)
40
How an Amphibian Breathes
!  The process that ventilates the lungs is breathing,
the alternate inhalation and exhalation of air
30
How a Bird Breathes
!  An amphibian such as a frog ventilates its lungs by
positive pressure breathing, which forces air
down the trachea
20
10
RDS deaths
0
Deaths from
other causes
(n = 9) (n = 0)
<1,200 g
(n = 29) (n = 9)
≥1,200 g
!  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
!  Passage of air through the entire system of lungs
and air sacs requires two cycles of inhalation and
exhalation
!  Ventilation in birds is highly efficient
Body mass of infant
129
130
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Figure 42.26
131
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132
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Figure 42.26a
Anterior
air sacs
Posterior
air sacs
How a Mammal Breathes
Lungs
Airflow
Air tubes
(parabronchi)
in lung
Airflow
1 mm
Lungs
Posterior
air sacs
!  The tidal volume is the volume of air inhaled with
each breath
!  Lung volume increases as the rib muscles and
diaphragm contract
!  The maximum tidal volume is the vital capacity
!  After exhalation, a residual volume of air remains
in the lungs
Air tubes
(parabronchi)
in lung
Anterior
air sacs
3
!  Mammals ventilate their lungs by negative
pressure breathing, which pulls air into the lungs
1 mm
2
4
1
1 First inhalation
3 Second inhalation
2 First exhalation
4 Second exhalation
133
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134
135
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Figure 42.27
136
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Figure 42.28
Control of Breathing in Humans
NORMAL BLOOD pH
(about 7.4)
Rib cage
gets smaller
as rib muscles
relax.
Rib cage
expands as
rib muscles
contract.
Blood CO2 level falls
and pH rises.
!  In humans, breathing is usually regulated by
involuntary mechanisms
Medulla detects
decrease in pH of
cerebrospinal fluid.
!  The breathing control centers are found in the
medulla oblongata of the brain
Diaphragm
1 INHALATION: Diaphragm
contracts (moves down).
Cerebrospinal
fluid
!  The medulla regulates the rate and depth of
breathing in response to pH changes in the
cerebrospinal fluid
Lung
Signals from
medulla to rib
muscles and
diaphragm
increase rate
and depth of
ventilation.
2 EXHALATION: Diaphragm
relaxes (moves up).
137
Medulla
oblongata
!  Sensors in the aorta and carotid arteries monitor
O2 and CO2 concentrations in the blood
!  These signal the breathing control centers, which
respond as needed
!  Additional modulation of breathing takes place in
the pons, next to the medulla
Carotid
arteries
Aorta
138
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Blood pH falls
due to rising levels of
CO2 in tissues (such as
when exercising).
Sensors in major
blood vessels
detect decrease
in blood pH.
Medulla receives
signals from major
blood vessels.
139
140
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Figure 42.29
Concept 42.7: Adaptations for gas exchange
include pigments that bind and transport gases
Coordination of Circulation and Gas Exchange
27
!  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
!  The metabolic demands of many organisms
require that the blood transport large quantities
of O2 and CO2
160
!  In the alveoli, O2 diffuses into the blood and CO2
diffuses into the air
40
CO2
O2
1
Alveolar
spaces 2
Alveolar
capillaries
Blood
entering
alveolar
capillaries
45
PO 2 PCO 2
0.2
104
40
PO 2 PCO 2
5
Pulmonary
veins and
systemic 3
arteries
Pulmonary
arteries
and systemic
veins
104
40
PO 2 PCO 2
<40
>45
142
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Inhaled air
PO 2 PCO 2
Alveolar
epithelial
cells
PO 2 PCO 2
141
6 Exhaled air
PO 2 PCO 2
!  In tissue capillaries, partial pressure gradients
favor diffusion of O2 into the interstitial fluids and
CO2 into the blood
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Animation: CO2 from Blood to Lung
120
4 Body
tissue
CO2
O2
Systemic
capillaries
143
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144
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Animation: CO2 from Tissues to Blood
Animation: O2 from Blood to Tissues
145
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Animation: O2 from Lungs to Blood
BioFlix: Gas Exchange
146
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147
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148
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Figure 42.UN02
Respiratory Pigments
!  Respiratory pigments, proteins that transport
oxygen, greatly increase the amount of oxygen
that blood can carry
!  A single hemoglobin molecule can carry four
molecules of O2, one molecule for each ironcontaining heme group
!  CO2 produced during cellular respiration lowers
blood pH and decreases the affinity of hemoglobin
for O2; this is called the Bohr shift
!  Arthropods and many molluscs have hemocyanin
with copper as the oxygen-binding component
!  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
!  Hemoglobin plays a minor role in transport of CO2
and assists in buffering the blood
!  Most vertebrates and some invertebrates use
hemoglobin
Iron
Heme
Hemoglobin
!  In vertebrates, hemoglobin is contained within
erythrocytes
149
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O2 unloaded
to tissues
during
exercise
60
40
20
0
20
40
60
Tissues during Tissues
exercise
at rest
PO 2 (mm Hg)
80
100
Lungs
(a) PO 2 and hemoglobin dissociation at pH 7.4
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
100
100
80
(b) pH and hemoglobin dissociation
O2 unloaded
to tissues
during
exercise
60
40
20
0
PO 2 (mm Hg)
O2 unloaded
to tissues
at rest
0
20
40
60
Tissues during Tissues
exercise
at rest
PO2 (mm Hg)
153
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O2 saturation of hemoglobin (%)
O2 unloaded
to tissues
at rest
80
152
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Figure 42.30b
O2 saturation of hemoglobin (%)
100
151
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Figure 42.30a
O2 saturation of hemoglobin (%)
O2 saturation of hemoglobin (%)
Figure 42.30
0
150
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80
100
(a) PO 2 and hemoglobin dissociation at pH 7.4
pH 7.4
80
!  Some CO2 from respiring cells diffuses into the
blood and is transported in blood plasma, bound to
hemoglobin
pH 7.2
Hemoglobin
retains less
O2 at lower pH
(higher CO2
concentration)
60
40
!  The remainder diffuses into erythrocytes and
reacts with water to form H2CO3, which dissociates
into H+ and bicarbonate ions (HCO3−)
20
0
Lungs
Carbon Dioxide Transport
100
0
20
40
60
80
!  In the lungs the relative partial pressures of CO2
favor the net diffusion of CO2 out of the blood
100
PO2 (mm Hg)
(b) pH and hemoglobin dissociation
154
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155
156
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Figure 42.UN03
Figure 42.UN01a
Respiratory Adaptations of Diving Mammals
!  Diving mammals have evolutionary adaptations
that allow them to perform extraordinary feats
!  Deep-diving air breathers stockpile O2 and deplete
it slowly
!  For example, Weddell seals in Antarctica can
remain underwater for 20 minutes to an hour
!  Diving mammals can store oxygen in their muscles
in myoglobin proteins
!  For example, elephant seals can dive to 1,500 m
and remain underwater for 2 hours
!  Diving mammals also conserve oxygen by
!  Changing their buoyancy to glide passively
!  These animals have a high blood to body
volume ratio
!  Decreasing blood supply to muscles
Weddell seal
157
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158
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!  Deriving ATP in muscles from fermentation once
oxygen is depleted
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159
160
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Figure 42.UN04
Figure 42.UN05
Alveolar
epithelial
cells
Figure 42.UN06
Inhaled air
Exhaled air
Alveolar
spaces
CO2
O2
O2 saturation of
hemoglobin (%)
Figure 42.UN01b
Alveolar
capillaries
Pulmonary
veins
Pulmonary
arteries
Systemic
veins
Systemic
arteries
O2
80
60
Systemic
capillaries
Fetus
Mother
40
20
0
Heart
CO2
100
0 20 40 60 80 100
PO2 (mm Hg)
Body tissue
161
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162
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163
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164
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