Biology in Focus - Chapter 34 - Circulation and Gas Exchange

1. CAMPBELL BIOLOGY IN FOCUS
© 2014 Pearson Education, Inc.
Urry • Cain • Wasserman • Minorsky • Jackson • Reece
Lecture Presentations by
Kathleen Fitzpatrick and Nicole Tunbridge
34
Circulation and
Gas Exchange

2. © 2014 Pearson Education, Inc.
Overview: Trading Places
 The resources that animal cells require, such as
nutrients and O2, enter the cytoplasm by crossing
the plasma membrane
 In unicellular organisms, these exchanges occur
directly with the environment
 Most multicellular organisms rely on specialized
systems that carry out exchange with the environment
and transport materials through the body

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 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

4. © 2014 Pearson Education, Inc.
Figure 34.1

5. © 2014 Pearson Education, Inc.
Concept 34.1: Circulatory systems link exchange
surfaces with cells throughout the body
 Small, nonpolar molecules such as O2 and CO2
move between cells and their immediate
surroundings by diffusion
 Diffusion time is proportional to the square of the
distance travelled
 Diffusion is only efficient over small distances

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 In small 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

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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 flat
body shape to optimize diffusional exchange with
the environment

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Figure 34.2
Gastrovascular
cavity
Mouth
1 mm

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Open and Closed Circulatory Systems
 A circulatory system has a circulatory fluid, a set
of interconnecting vessels, and a muscular pump,
the heart
 Several basic types of circulatory systems have
arisen during evolution, each representing
adaptations to constraints of anatomy and
environment

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 All circulatory systems are either open or closed
 In insects, other arthropods, and some molluscs,
circulatory fluid bathes the organs directly in an
open circulatory system
 In an open circulatory system, there is no distinction
between circulatory fluid and interstitial fluid, and
this general body fluid is called hemolymph

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Figure 34.3
Branch vessels
in each organ
Tubular heart
Pores
Hemolymph in sinuses
(a) An open circulatory system
Heart
(b) A closed circulatory system
Heart
Blood
Dorsal vessel
(main heart)
Auxiliary
hearts
Ventral vessels
Interstitial
fluid

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Figure 34.3a
Tubular heart
Pores
Hemolymph in sinuses
(a) An open circulatory system
Heart

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 In closed circulatory systems the circulatory fluid
called blood is confined to vessels and is distinct
from interstitial fluid
 These systems are found in annelids, most
cephalopods, and all vertebrates
 One or more hearts pump blood through the vessels
 Chemical exchange occurs between blood and
interstitial fluid and between interstitial fluid and
body cells

14. © 2014 Pearson Education, Inc.
Figure 34.3b
Branch vessels
in each organ
(b) A closed circulatory system
Heart
Blood
Dorsal vessel
(main heart)
Auxiliary
hearts
Ventral vessels
Interstitial
fluid

15. © 2014 Pearson Education, Inc.
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 34.4
Lung
and skin
capillaries
Body capillaries
Vein
Gill capillaries
(a) Single circulation: fish
Heart:
(b) Double circulation:
amphibian
Key
Systemic
capillaries
Pulmocutaneous
circuit
Artery
Ventricle (V)
Atrium (A)
Oxygen-rich blood
Oxygen-poor blood
Right Left
A A
V
Systemic circuit
Lung
capillaries
(c) Double circulation:
mammal
Systemic
capillaries
Pulmonary
circuit
Right Left
A A
V
Systemic circuit
V

20. © 2014 Pearson Education, Inc.
Figure 34.4a
Body capillaries
Vein
Gill capillaries
(a) Single circulation: fish
Heart:
Key
Artery
Ventricle (V)
Atrium (A)
Oxygen-rich blood
Oxygen-poor blood

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Double Circulation
 Amphibians, reptiles, and mammals have double
circulation
 Oxygen-poor and oxygen-rich blood is pumped
separately from the right and left sides of the heart
 Having both pumps within a heart simplifies
coordination of the pumping cycle

22. © 2014 Pearson Education, Inc.
Figure 34.4b
Lung
and skin
capillaries
(b) Double circulation:
amphibian
Key
Systemic
capillaries
Pulmocutaneous
circuit
Oxygen-rich blood
Oxygen-poor blood
Right Left
A A
V
Systemic circuit

23. © 2014 Pearson Education, Inc.
Figure 34.4c
Key
Oxygen-rich blood
Oxygen-poor blood
Lung
capillaries
(c) Double circulation:
mammal
Systemic
capillaries
Pulmonary
circuit
Right Left
A A
V
Systemic circuit
V

24. © 2014 Pearson Education, Inc.
 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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Evolutionary Variation in Double Circulation
 Some vertebrates with double circulation are
intermittent breathers
 These animals have adaptations that enable the
circulatory system temporarily to bypass the lungs

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 Frogs and other amphibians have a three-
chambered 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

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 Turtles, snakes, and lizards have a three-chambered
heart: two atria and one ventricle
 Their circulatory system allows control of relative
amounts of blood flowing to the lungs and body
 In alligators, caimans, and other crocodilians a
septum divides the ventricle
 A connection to atrial valves can temporarily shunt
blood away from the lungs, as needed

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 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
 There is no mechanism to vary relative blood flow to
the lungs and body
 Mammals and birds are endotherms and require
more O2 than ectotherms

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Concept 34.2: 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 via the pulmonary arteries
 The blood loads O2 and unloads CO2 in the capillary
beds of the lungs
 Oxygen-rich blood from the lungs enters the heart at
the left atrium via the pulmonary veins and is
pumped through the aorta to the body tissues by the
left ventricle

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 The aorta provides blood to the heart through the
coronary arteries
 Diffusion of O2 and CO2 takes place in the capillary
beds throughout the body
 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

32. © 2014 Pearson Education, Inc.
Figure 34.5
Capillaries of
abdominal organs
and hind limbs
Aorta
Capillaries
of right lung
Superior
vena cava
Pulmonary
artery
Pulmonary
vein
Right atrium
Right ventricle
Inferior vena cava
Capillaries
of left lung
Pulmonary artery
Pulmonary
vein
Left atrium
Left ventricle
Capillaries of
head and
forelimbs
Aorta9
7
6
4
2
11
3
5
8
10
1
3

33. © 2014 Pearson Education, Inc.
The Mammalian Heart: A Closer Look
 A closer look at the mammalian heart provides a
better understanding of double circulation
 When the heart contracts, it pumps blood; when it
relaxes, its chambers fill with blood
 One complete sequence of pumping and filling is
called the cardiac cycle

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 Atria have relatively thin walls and serve as
collection chambers for blood returning to the heart
 The ventricles are more muscular and contract much
more forcefully than the atria
 The volume of blood each ventricle pumps per
minute is called the cardiac output

35. © 2014 Pearson Education, Inc.
Figure 34.6
Aorta
Atrioventricular
(AV) valve
Semilunar
valve
Pulmonary artery
Right
atrium
Right
ventricle
Pulmonary
artery
Left
atrium
Left
ventricle
Atrioventricular
(AV) valve
Semilunar
valve

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Figure 34.7-1
Atrial and
ventricular
diastole
0.4
sec
1

37. © 2014 Pearson Education, Inc.
Figure 34.7-2
Atrial and
ventricular
diastole
Atrial systole and
ventricular diastole
0.4
sec
0.1
sec
1
2

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Figure 34.7-3
Atrial and
ventricular
diastole
Atrial systole and
ventricular diastole
Ventricular systole
and atrial diastole
0.4
sec
0.3 sec
0.1
sec
1
2
3

39. © 2014 Pearson Education, Inc.
 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
 Cardiac output 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

42. © 2014 Pearson Education, Inc.
Maintaining the Heart’s Rhythmic Beat
 Some cardiac muscle cells are autorhythmic,
meaning they contract without any signal from the
nervous system
 The sinoatrial (SA) node, or pacemaker, sets the
rate and timing at which all other cardiac muscle
cells contract
 The SA node produces electrical impulses that
spread rapidly through the heart and can be
recorded as an electrocardiogram (ECG or EKG)

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Figure 34.8-1
Signals (yellow)
from SA node
spread
through atria.
SA node
(pacemaker)
1
ECG

44. © 2014 Pearson Education, Inc.
Figure 34.8-2
Signals (yellow)
from SA node
spread
through atria.
SA node
(pacemaker)
1 Signals are
delayed
at AV node.
AV
node
ECG
2

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Figure 34.8-3
Signals (yellow)
from SA node
spread
through atria.
SA node
(pacemaker)
1 Signals are
delayed
at AV node.
Bundle
branches
pass signals
to heart apex.
AV
node
Bundle
branches Heart
apex
ECG
2 3

46. © 2014 Pearson Education, Inc.
Figure 34.8-4
Signals (yellow)
from SA node
spread
through atria.
SA node
(pacemaker)
1 Signals are
delayed
at AV node.
Bundle
branches
pass signals
to heart apex.
Signals
spread
throughout
ventricles.
AV
node
Bundle
branches Heart
apex
Purkinje
fibers
ECG
2 3 4

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 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

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Concept 34.3: 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 apply to 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
to blood flow

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 Capillaries have thin walls, the endothelium and its
basal lamina, to facilitate the exchange of
substances
 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

52. © 2014 Pearson Education, Inc.
Figure 34.9
Connective
tissue
Smooth
muscle
Connective
tissue
Smooth
muscle
Endothelium Endothelium
Artery Vein
Artery Vein
Red blood
cells
Basal lamina
Capillary
Red blood cell
Capillary
Arteriole
Venule
Valve100 µm
15µm
LM
LM

53. © 2014 Pearson Education, Inc.
Figure 34.9a
Connective
tissue
Smooth
muscle
Connective
tissue
Smooth
muscle
Endothelium
Endothelium
Artery Vein
Basal lamina
Capillary
Arteriole
Venule
Valve

54. © 2014 Pearson Education, Inc.
Figure 34.9b
Artery Vein
Red blood
cells
100 µm
LM

55. © 2014 Pearson Education, Inc.
Figure 34.9c
Red blood cell
Capillary
15µm
LM

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Blood Flow Velocity
 Blood vessel diameter influences blood flow
 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

57. © 2014 Pearson Education, Inc.
Figure 34.10
Systolic
pressure
Diastolic
pressure
4,000
2,000
120
20
40
80
40
0
0
0
Pressure
(mmHg)
Velocity
(cm/sec)
Area(cm2
)
Aorta
Arteries
Venae
cavae
Veins
Capillaries
Venules
Arterioles

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Blood Pressure
 Blood flows from areas of higher pressure to areas
of lower pressure
 Blood pressure exerts a force in all directions

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Changes in Blood Pressure During the Cardiac
Cycle
 Systole is the contraction phase of the cardiac cycle
 Pressure at the time of ventricle contraction is called
systolic pressure
 Diastole is the the relaxation phase of the cardiac
cycle; diastolic pressure is lower than systolic

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Maintenance 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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 Fainting is caused by inadequate blood flow to the
head
 Animals with long necks require a higher systolic
pressure to pump blood against gravity
 Gravity is a consideration for blood flow in veins,
particularly in the legs
 One-way valves in veins prevent backflow of blood
 Blood returns to the heart through contraction of
smooth muscle in the walls of veins and venules and
by contraction of skeletal muscles

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Figure 34.11
Direction of blood
flow in vein
(toward heart)
Valve (open)
Valve (closed)
Skeletal muscle

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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 alter blood flow in capillary beds
 Vasoconstriction or vasodilation of the arteriole that
supplies a capillary bed
 Precapillary sphincters, rings of smooth muscle at the
capillary bed entrance, open and close to regulate
passage of blood
 Critical exchange of substances takes place across
the thin walls of the capillaries

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 Blood pressure tends to drive fluid out of the
capillaries
 The difference in solute concentration between blood
and interstitial fluid (the blood’s osmotic pressure)
opposes fluid movement from the capillaries
 Blood pressure is usually greater than osmotic
pressure
 Net loss of fluid from capillaries occurs in regions
where blood pressure is highest

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Fluid Return by the Lymphatic System
 The lymphatic system returns fluid, called lymph,
that leaks out from the capillary beds
 Lymph has a very similar composition to interstitial
fluid
 The lymphatic system drains into veins in the neck
 Valves in lymph vessels prevent the backflow of
fluid

68. © 2014 Pearson Education, Inc.
Figure 34.12
Interstitial
fluid
Lymphatic
vessel
Lymphatic
vessel
Blood
capillary
Tissue cells
Lymph node
Masses of
defensive
cells
Lymphatic
vessels
Lymph
nodes
Peyer’s patches
(small intestine)
Appendix
(cecum)
Thymus
(immune
system)
Adenoid
Tonsils
Spleen

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 Lymph vessels have valves to prevent backflow
 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
 The lymphatic system also plays a role in harmful
immune responses, such as those responsible for
asthma

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Concept 34.4: Blood components function in
exchange, transport, and defense
 With open circulation, the fluid that is pumped
comes into direct contact with all cells and has
the same composition as interstitial fluid
 The closed circulatory systems of vertebrates
contain blood, which can be much more highly
specialized

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Blood Composition and Function
 Blood is a connective tissue consisting of cells
suspended in a liquid matrix called plasma
 The cellular elements occupy about 45% of the
volume of blood
Video: Leukocyte Rolling

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Figure 34.13
Separated
blood
elements
Solvent for
carrying other
substances
Plasma 55% Cellular elements 45%
Constituent Major functions
Osmotic balance,
pH buffering,
and regulation
of membrane
permeability
Water
Ions (blood
electrolytes)
Sodium
Potassium
Calcium
Magnesium
Chloride
Bicarbonate
Osmotic balance,
pH buffering
Clotting
Defense
Fibrinogen
Plasma proteins
Albumin
Immunoglobulins
(antibodies)
Substances transported by blood
Nutrients (such as glucose, fatty
acids, vitamins)
Waste products of metabolism
Respiratory gases (O2 and CO2)
Hormones
Functions
Leukocytes (white blood cells)
Transport
of O2 and
some CO2
Cell type
Number
per µL (mm3)
of blood
Basophils
Lymphocytes
Eosinophils
Neutrophils Monocytes
Platelets
Erythrocytes (red blood cells)
250,000–400,000
5,000,000–
6,000,000
Blood
clotting
5,000–10,000 Defense
and
immunity

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Figure 34.13a
Solvent for carrying other
substances
Plasma 55%
Constituent Major functions
Osmotic balance, pH buffering,
and regulation of membrane
permeability
Water
Ions (blood electrolytes)
Sodium
Potassium
Calcium
Magnesium
Chloride
Bicarbonate
Osmotic balance, pH buffering
Clotting
Defense
Fibrinogen
Plasma proteins
Albumin
Immunoglobulins
(antibodies)
Substances transported by blood
Nutrients (such as glucose, fatty acids, vitamins)
Waste products of metabolism
Respiratory gases (O2 and CO2)
Hormones

74. © 2014 Pearson Education, Inc.
Figure 34.13b
Cellular elements 45%
Functions
Leukocytes (white blood cells)
Transport of O2 and
some CO2
Cell type
Number
per µL (mm3
) of blood
Basophils
Lymphocytes
Eosinophils
Neutrophils
Monocytes
Platelets
Erythrocytes (red blood cells)
250,000–400,000
5,000,000–6,000,000
Blood clotting
5,000–10,000 Defense and
immunity

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Plasma
 Blood plasma is about 90% water
 Among its solutes are inorganic salts in the form of
dissolved ions, sometimes called electrolytes
 Plasma proteins influence blood pH, osmotic
pressure, and viscosity
 Particular plasma proteins function in lipid transport,
immunity, and blood clotting

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Cellular Elements
 Blood contains two classes of cells
 Red blood cells (erythrocytes) transport O2
 White blood cells (leukocytes) function in defense
 Platelets, a third cellular element, are fragments of
cells that are involved in clotting

77. © 2014 Pearson Education, Inc.
Figure 34.14
Stem cells
(in bone marrow)
Basophils
Lymphocytes
Eosinophils
Neutrophils
Monocytes
Platelets
Erythrocytes
Myeloid
stem cells
Lymphoid
stem cells
B cells T cells

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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

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 Sickle-cell disease is caused by abnormal
hemoglobin that polymerizes into aggregates
 The aggregates can distort an erythrocyte into a
sickle shape

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 Through a person’s life, multipotent stem cells
replace the worn-out cellular elements of blood
 Erythrocytes circulate for about 120 days before
they are replaced
 Stem cells that produce red blood cells and platelets
are located in red marrow of bones like the ribs,
vertebrae, sternum, and pelvis

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Leukocytes
 There are five major types of white blood cells, or
leukocytes
 They function in defense by engulfing bacteria and
debris or by mounting immune responses against
foreign substances
 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, which forms the framework of a
clot
 A blood clot formed within a blood vessel is called a
thrombus and can block blood flow

84. © 2014 Pearson Education, Inc.
Figure 34.15
Platelet
Platelet
plug
Collagen
fibers
Platelets
Clotting factors from:
Damaged cells
Plasma (factors include calcium, vitamin K)
Fibrin
Thrombin
Fibrinogen
Prothrombin
Enzymatic cascade
Fibrin clot
Fibrin clot
formation
Red blood cell 5 µm
1 2 3

85. © 2014 Pearson Education, Inc.
Figure 34.15a
Platelet
Platelet
plug
Collagen
fibers
Platelets
Clotting factors from:
Damaged cells
Plasma (factors include calcium, vitamin K)
Fibrin
Thrombin
Fibrinogen
Prothrombin
Enzymatic cascade
Fibrin clot
Fibrin clot
formation
1 2 3

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Figure 34.15b
Fibrin
clot
Red blood cell 5 µm

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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 normal
membrane fluidity

88. © 2014 Pearson Education, Inc.
 Low-density lipoprotein (LDL) delivers cholesterol
to cells for membrane production
 High-density lipoprotein (HDL) scavenges excess
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

89. © 2014 Pearson Education, Inc.
Atherosclerosis, Heart Attacks, and Stroke
 One type of cardiovascular disease, atherosclerosis,
is caused by the buildup of fatty deposits within
arteries
 A fatty deposit is called a plaque; as it grows, the
artery walls become thick and stiff and the obstruction
of the artery increases

90. © 2014 Pearson Education, Inc.
Figure 34.16
Endothelium
Lumen
Plaque
Blood clot

91. © 2014 Pearson Education, Inc.
 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 may cause chest pain

92. © 2014 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 is increased by
smoking and consumption of trans fats and
decreased by exercise
 Drugs called statins reduce LDL levels and risk of
heart attacks

93. © 2014 Pearson Education, Inc.
 Inflammation plays a role in atherosclerosis and
thrombus formation
 Aspirin inhibits inflammation and reduces the risk of
heart attacks and stroke
 Hypertension (high blood pressure) contributes to
the risk of heart attack and stroke
 Hypertension can be reduced by dietary changes,
exercise, medication, or some combination of these

94. © 2014 Pearson Education, Inc.
Concept 34.5: Gas exchange occurs across
specialized respiratory surfaces
 Gas exchange is the uptake of molecular O2 from
the environment and the discharge of CO2 to the
environment

95. © 2014 Pearson Education, Inc.
Partial Pressure Gradients in Gas Exchange
 Partial pressure is the pressure exerted by a
particular gas in a mixture of gases
 For example, the atmosphere is 21% O2, by volume,
so the partial pressure of O2 (PO2
) is 0.21 × the
atmospheric pressure

96. © 2014 Pearson Education, Inc.
 Partial pressures also apply to gases dissolved in
liquid, such as water
 When water is exposed to air, an equilibrium is
reached in which the partial pressure of each gas is
the same in the water and the air
 A gas always undergoes net diffusion from a region
of higher partial pressure to a region of lower partial
pressure

97. © 2014 Pearson Education, Inc.
Respiratory Media
 O2 is plentiful in air, and breathing air is relatively
easy
 In a given volume, there is less O2 available in water
than in air
 Obtaining O2 from water requires greater energy
expenditure than air breathing
 Aquatic animals have a variety of adaptations to
improve efficiency in gas exchange

98. © 2014 Pearson Education, Inc.
Figure 34.17
Coelom
Tube foot
Gills
(b) Sea star(a) Marine worm
Parapodium (functions as gill)

99. © 2014 Pearson Education, Inc.
Figure 34.17a
(a) Marine worm

100. © 2014 Pearson Education, Inc.
Figure 34.17b
(b) Sea star

101. © 2014 Pearson Education, Inc.
Respiratory Surfaces
 Gas exchange across respiratory surfaces takes
place by diffusion
 Respiratory surfaces tend to be large and thin and
are always moist
 Respiratory surfaces vary by animal and can include
the skin, gills, tracheae, and lungs

102. © 2014 Pearson Education, Inc.
Gills in Aquatic Animals
 Gills are outfoldings of the body that create a large
surface area for gas exchange
 Ventilation is the movement of the respiratory
medium over the respiratory surface
 Ventilation maintains the necessary partial pressure
gradients of O2 and CO2 across the gills

103. © 2014 Pearson Education, Inc.
 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
 Countercurrent exchange mechanisms are
remarkably efficient

104. © 2014 Pearson Education, Inc.
Figure 34.18
Lamella
Water flow
Countercurrent exchange
O2-poor blood
Gill filaments
Operculum
Gill
arch
Water
flow
Gill arch
Blood
vessels
O2-rich blood
Blood flow
PO2
(mm Hg)
in blood
PO2
(mm Hg) in water
Net
diffusion
of O2
140 110 80 50 30
150 120 90 60 30

105. © 2014 Pearson Education, Inc.
Tracheal Systems in Insects
 The tracheal system of insects consists of a
network of air tubes that branch throughout the
body
 The tracheal system can transport O2 and CO2
without the participation of the animal’s open
circulatory system
 Larger insects must ventilate their tracheal system
to meet O2 demands

106. © 2014 Pearson Education, Inc.
Figure 34.19
Tracheoles Muscle fiberMitochondria
Tracheae
Air sacs
External opening
Air
sac Tracheole
Trachea
Air
2.5µm
Body
cell

107. © 2014 Pearson Education, Inc.
Figure 34.19a
Tracheoles Muscle fiberMitochondria
2.5µm

108. © 2014 Pearson Education, Inc.
Lungs
 Lungs are an infolding of the body surface, usually
divided into numerous pockets
 The circulatory system (open and closed) transports
gases between the lungs and the rest of the body
 The use of lungs for gas exchange varies among
vertebrates that lack gills

109. © 2014 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

110. © 2014 Pearson Education, Inc.
 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

111. © 2014 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
Animation: Gas Exchange

112. © 2014 Pearson Education, Inc.
Figure 34.20
Bronchiole
Bronchus
Right lung
Trachea
(Esophagus)
Larynx
Pharynx
(Heart)
Terminal
bronchiole
Left
lung
Nasal
cavity
Capillaries
Alveoli
Dense capillary bed
enveloping alveoli
(SEM)
Branch of
pulmonary vein
(oxygen-rich
blood)
Branch of pulmonary
artery (oxygen-poor
blood)
50 µm
Diaphragm

113. © 2014 Pearson Education, Inc.
Figure 34.20a
Bronchiole
Bronchus
Right lung
Trachea
(Esophagus)
Larynx
Pharynx
(Heart)
Left
lung
Nasal
cavity
Diaphragm

114. © 2014 Pearson Education, Inc.
Figure 34.20b
Terminal
bronchiole
Capillaries
Alveoli
Branch of
pulmonary vein
(oxygen-rich
blood)
Branch of pulmonary
artery (oxygen-poor
blood)

115. © 2014 Pearson Education, Inc.
Figure 34.20c
Dense capillary bed
enveloping alveoli (SEM)
50 µm

116. © 2014 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

117. © 2014 Pearson Education, Inc.
Figure 34.21
Deaths from
other causes
RDS deaths
Body mass of infant
<1,200 g >1,200 g
(n = 9) (n = 0) (n = 29) (n = 9)
Surfacetension(dynes/cm)
Results
10
20
30
40
0

118. © 2014 Pearson Education, Inc.
Concept 34.6: Breathing ventilates the lungs
 The process that ventilates the lungs is breathing,
the alternate inhalation and exhalation of air

119. © 2014 Pearson Education, Inc.
 An amphibian such as a frog ventilates its lungs by
positive pressure breathing, which forces air down
the trachea
 Birds have eight or nine air sacs that function as
bellows that keep air flowing through the lungs
 Air passes through the lungs of birds in one direction
only
 Passage of air through the entire system—lungs and
air sacs—requires two cycles in inhalation and
exhalation

120. © 2014 Pearson Education, Inc.
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
Animation: Gas Exchange

121. © 2014 Pearson Education, Inc.
Figure 34.22
Inhalation:
Diaphragm contracts
(moves down).
Diaphragm
Exhalation:
Diaphragm relaxes
(moves up).
Lung
Air
inhaled.
Air
exhaled.
Rib cage
expands as
rib muscles
contract.
Rib cage gets
smaller as
rib muscles
relax.
1 2

122. © 2014 Pearson Education, Inc.
 The maximum tidal volume is the vital capacity
 After exhalation, a residual volume of air remains
in the lungs
 Each inhalation mixes fresh air with oxygen-depleted
residual air
 As a result, the maximum PO2
in alveoli is considerably
less than in the atmosphere

123. © 2014 Pearson Education, Inc.
Control of Breathing in Humans
 In humans, the main breathing control center
consists of neural circuits in the medulla oblongata,
near the base of the brain
 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

124. © 2014 Pearson Education, Inc.
Figure 34.23-1
Homeostasis:
Blood pH of about 7.4
Stimulus:
Rising level of CO2
in tissues lowers
blood pH.

125. © 2014 Pearson Education, Inc.
Figure 34.23-2
Carotid
arteries
Homeostasis:
Blood pH of about 7.4
Stimulus:
Rising level of CO2
in tissues lowers
blood pH.
Sensor/control
center:
Aorta
Cerebro-
spinal
fluid
Medulla
oblongata

126. © 2014 Pearson Education, Inc.
Figure 34.23-3
Carotid
arteries
Response:
Signals from
medulla to rib
muscles and
diaphragm
increase rate
and depth of
ventilation.
Homeostasis:
Blood pH of about 7.4
Stimulus:
Rising level of CO2
in tissues lowers
blood pH.
Sensor/control
center:
Aorta
Cerebro-
spinal
fluid
Medulla
oblongata

127. © 2014 Pearson Education, Inc.
Figure 34.23-4
Carotid
arteries
Response:
Signals from
medulla to rib
muscles and
diaphragm
increase rate
and depth of
ventilation.
Homeostasis:
Blood pH of about 7.4
CO2 level
decreases. Stimulus:
Rising level of CO2
in tissues lowers
blood pH.
Sensor/control
center:
Aorta
Cerebro-
spinal
fluid
Medulla
oblongata

128. © 2014 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

129. © 2014 Pearson Education, Inc.
Concept 34.7: 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

130. © 2014 Pearson Education, Inc.
Coordination of Circulation and Gas Exchange
 Blood arriving in the lungs has a low PO2
and a high
PCO2
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
 Specialized carrier proteins play a vital role in this
process

131. © 2014 Pearson Education, Inc.
Animation: O2 Blood to Tissues
Animation: O2 Lungs to Blood
Animation: CO2 Blood to Lungs
Animation: CO2 Tissues to Blood

132. © 2014 Pearson Education, Inc.
Figure 34.24
Alveolar
epithelial
cells
Alveolar
spaces
Alveolar
capillaries
Inhaled airExhaled air
Pulmonary
veins
Systemic
arteries
Pulmonary
arteries
Systemic
veins
Systemic
capillaries
Heart
CO2 O2
Body tissue
cells
O2 CO2
120 27
O2 CO2
40 45
O2 CO2
160 0.2
O2 CO2
104 40
O2 CO2
<40 >45
O2CO2

133. © 2014 Pearson Education, Inc.
Respiratory Pigments
 Respiratory pigments circulate in blood or
hemolymph and greatly increase the amount of
oxygen that is transported
 A variety of respiratory pigments have evolved
among animals
 These mainly consist of a metal bound to a protein

134. © 2014 Pearson Education, Inc.
 The respiratory pigment of almost all vertebrates
and many invertebrates is hemoglobin
 A single hemoglobin molecule can carry four
molecules of O2, one molecule for each iron-
containing heme group
 Hemoglobin binds oxygen reversibly, loading it in
the gills or lungs and releasing it in other parts of
the body

135. © 2014 Pearson Education, Inc.
Figure 34.UN01
Hemoglobin
Heme
Iron

136. © 2014 Pearson Education, Inc.
 Hemoglobin binds O2 cooperatively
 When O2 binds one subunit, the others change shape
slightly, resulting in their increased affinity for oxygen
 When one subunit releases O2, the others release their
bound O2 more readily
 Cooperativity can be demonstrated by the dissociation
curve for hemoglobin

137. © 2014 Pearson Education, Inc.
Figure 34.25
pH 7.4
PO2
(mm Hg)
pH 7.2
Hemoglobin
retains less
O2 at lower pH
(higher CO2
concentration
Tissues
at rest
PO2
(mm Hg)
Tissues during
exercise
Lungs
O2 unloaded
to tissues
during exercise
O2 unloaded
to tissues
at rest
(b) pH and hemoglobin dissociation(a) PO2
and hemoglobin dissociation
at pH 7.4
O2saturationofhemoglobin(%)
O2saturationofhemoglobin(%)
100
80
60
40
20
0
100
80
60
40
20
0
100806040200 100806040200

138. © 2014 Pearson Education, Inc.
Figure 34.25a
Tissues
at rest
PO2
(mm Hg)
Tissues during
exercise
Lungs
O2 unloaded
to tissues
during exercise
O2 unloaded
to tissues
at rest
(a) PO2
and hemoglobin dissociation
at pH 7.4
O2saturationofhemoglobin(%)
100
80
60
40
20
0
100806040200

139. © 2014 Pearson Education, Inc.
 CO2 produced during cellular respiration lowers
blood pH and decreases the affinity of hemoglobin
for O2; this is called the Bohr shift
 Hemoglobin also assists in preventing harmful
changes in blood pH and plays a minor role in CO2
transport

140. © 2014 Pearson Education, Inc.
Figure 34.25b
pH 7.4
PO2
(mm Hg)
pH 7.2
Hemoglobin
retains less
O2 at lower pH
(higher CO2
concentration
(b) pH and hemoglobin dissociation
O2saturationofhemoglobin(%)
100
80
60
40
20
0
100806040200

141. © 2014 Pearson Education, Inc.
Carbon Dioxide Transport
 Most of the CO2 from respiring cells diffuses into the
blood and is transported in blood plasma, bound to
hemoglobin or as bicarbonate ions (HCO3
–
)

142. © 2014 Pearson Education, Inc.
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

143. © 2014 Pearson Education, Inc.
 Deep-diving air breathers can store large amounts
of O2
 Oxygen can be stored 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

144. © 2014 Pearson Education, Inc.
Figure 34.UN02a
Plasma LDL cholesterol (mg/dL)
Percentofindividuals
30
20
10
0
3002502001501000
Individuals with an inactivating mutation in one copy
of PCSK9 gene (study group)
50

145. © 2014 Pearson Education, Inc.
Figure 34.UN02b
Plasma LDL cholesterol (mg/dL)
Percentofindividuals
30
20
10
0
3002502001501000
Individuals with two functional copies of PCSK9 gene
(control group)
50

146. © 2014 Pearson Education, Inc.
Figure 34.UN03
Alveolar
epithelial
cells
Pulmonary
arteries
Systemic
veins
Pulmonary
veins
Systemic
arteries
Systemic
capillaries
Alveolar
capillaries
Alveolar
spaces
Exhaled air Inhaled air
Heart
Body tissue
CO2
CO2
O2
O2

147. © 2014 Pearson Education, Inc.
Figure 34.UN04
Fetus
PO2
(mm Hg)
O2saturationof
hemoglobin(%)
Mother
100
80
60
40
20
0
100806040200