Transcript Chapter 22: Respiration

BIOLOGY
CONCEPTS & CONNECTIONS
Fourth Edition
Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor
CHAPTER 22
Respiration: The Exchange of
Gases
From PowerPoint® Lectures for Biology: Concepts & Connections
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Surviving in Thin Air
• The air at the height of the world’s highest
peak, Mt. Everest, is very low in oxygen
– Even expert mountain climbers do not always
survive the journey
– Thin air can weaken
muscles, damage
the digestive system,
cloud the mind, and
sometimes fill the
lungs with blood
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• Geese have adaptations that allow them to fly
over the Himalayas
– Their efficient lungs draw more oxygen from the
atmosphere
– Their hemoglobin has a high affinity for oxygen
– They have a large
number of capillaries
to deliver this oxygenrich blood to tissues
and muscles
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MECHANISMS OF GAS EXCHANGE
• Gas exchange is the interchange of O2 and CO2
between an organism and its environment
– It is also called respiration
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22.1 Overview: Gas exchange involves breathing,
the transport of gases, and the servicing of
tissue cells
• Gas exchange is essential because energy
metabolism requires O2 and produces CO2
• There are three phases of gas exchange
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O2
Lung
CO2
1 Breathing
Circulatory
system
2 Transport
of gases by
the circulatory
system
Mitochondria
3 Servicing of
O2
cells within
the body
tissues
CO2
Capillary
Cell
Figure 22.1
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22.2 Animals exchange O2 and CO2 through moist
body surfaces
• O2 enters an animal and CO2 leaves by diffusion
through a respiratory surface
– Respiratory surfaces are made up of living cells
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• Some animals use their entire skin as a gasexchange organ
– Example: earthworms
Cut
Cross section
of respiratory
surface (the
skin covering
the body)
CO2
O2
Capillaries
Figure 22.2A
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• In most animals, specialized body parts carry
out gas exchange
– Gills in fish
Body surface
Respiratory
surface
(gill)
CO2
Capillaries
O2
Figure 22.2B
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– Lungs in land
vertebrates
– Tracheae in
insects
Body surface
Body surface
Respiratory
surface
(tracheae)
O2
Body cells
(no capillaries)
Respiratory
surface
(within lung)
CO2
O2
Capillary
CO2
Figure 22.2C, D
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22.3 Gills are adapted for gas exchange in aquatic
environments
• Gills are extensions of the body that absorb O2
dissolved in water
• In fish, gill filaments bear numerous platelike
lamellae
– Lamellae are packed with blood vessels
– They are the respiratory surfaces
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• The structure
of fish gills
Gill arch
Direction
of water
flow
Gill arch
Blood
vessels
Oxygen-poor
blood
Gill
filaments
Oxygen-rich
blood
Lamella
Water
flow
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Figure 22.3
22.4 Countercurrent flow in the gills enhances O2
transfer
• Blood flows through the lamellae in a direction
opposite to water flow
– This countercurrent
maintains a diffusion
gradient that
maximizes the
uptake of O2
Water flow
over
lamellae
Blood flow
through
lamellae
Figure 22.4
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22.5 The tracheal system of insects provides direct
exchange between the air and body cells
• Land animals exchange gases by breathing air
– Air contains more O2 and is easier to move than
water
– But water loss from the respiratory surfaces can
be a problem
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• In insects, a network of tracheal tubes carries
out gas exchange
– O2 diffuses from the finely branched tubes
directly into cells
Figure 22.5B
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Air sacs
Tracheae
Opening
for air
Body
cell
Tracheole
Air
sac
Trachea
Air
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Body wall
Figure 22.5A, C
22.6 Terrestrial vertebrates have lungs
• In humans and other mammals, air enters
through the nasal cavity
– It passes through the pharynx and larynx into
the trachea
– The trachea forks to form two bronchi
– Each bronchus branches into numerous
bronchioles
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• The human respiratory system
Nasal
cavity
Pharynx
(Esophagus)
Left lung
Larynx
Trachea
Right
lung
Bronchus
Bronchiole
Diaphragm
(Heart)
Figure 22.6A
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• The bronchioles end in clusters
of tiny sacs called alveoli
– Alveoli form the respiratory
surface of the lungs
– Oxygen diffuses
through the thin
walls of the
alveoli into
the blood
Figure 22.6C
Oxygen-rich
blood
Oxygen-poor
blood
Bronchiole
Alveoli
Blood capillaries
Figure 22.6B
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22.7 Connection: Smoking is one of the deadliest
assaults on our respiratory system
• Mucus and cilia in the respiratory passages
protect the lungs
– Pollutants, including tobacco smoke, can destroy
these protections
• Smoking kills about 430,000 Americans each
year
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• Smoking causes lung cancer and contributes to
heart disease
• Smoking also causes emphysema
– Cigarette smoke
makes alveoli
brittle, causing
them to rupture
– This reduces the
lungs’ capacity
for gas exchange
Figure 22.7A, B
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22.8 Breathing ventilates the lungs
• Breathing is the alternation of inhalation and
exhalation
Rib cage
expands as
rib muscles
contract
Air
inhaled
Rib cage
gets smaller
as rib muscles
relax
Air
exhaled
Lung
Diaphragm
INHALATION
Diaphragm contracts
(moves down)
EXHALATION
Diaphragm relaxes
(moves up)
Figure 22.8A
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• Vital capacity is the maximum volume of air we
can inhale and exhale
– But our lungs hold more than this amount
– The alveoli do not completely collapse
– A residual volume of “dead” air remains in the
lungs after exhalation
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• Other organisms, such as birds, have air sacs
– These structures act as bellows that keep air
flowing through the lungs
– However, they do not function directly in gas
exchange
Air
Air
Anterior
air sacs
Trachea
Posterior
air sacs
Lungs
Lungs
Air
tubes
in lung
INHALATION:
Air sacs fill
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EXHALATION:
Air sacs empty; lungs fill
1 mn
Figure 22.8B
22.9 Breathing is automatically controlled
• Breathing control centers are located in the
pons and medulla of the brain
– These automatic controls keep breathing in tune
with body needs
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• During exercise, the CO2 level in the blood rises,
lowering the blood pH
– This triggers
a cascade of
events
Brain
Cerebrospinal fluid
BREATHING CONTROL
CENTERS—stimulated by:
Pons
Medulla
CO2 increase / pH decrease
in blood
Nerve signal
indicating low
O2 level
Nerve signals
trigger
contraction
of muscles
O2 sensor
in artery
Diaphragm
Figure 22.9
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Rib muscles
TRANSPORT OF GASES IN THE BODY
22.10 Blood transports the respiratory gases, with
hemoglobin carrying the oxygen
• The heart pumps oxygen-poor blood to the
lungs
– In the lungs it picks up O2 and drops off CO2
– In the tissues, cells pick up CO2 and drop off O2
– Gases diffuse down pressure gradients in the
lungs and the tissues
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• Gas exchange in
the body
Figure 22.10A
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• Hemoglobin is a protein in red blood cells
– It carries most of the oxygen in the blood
Heme
group
Iron
atom
O2 loaded
in lungs
O2 unloaded
in tissues
O2
O2
Polypeptide chain
Figure 22.10B
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22.11 Hemoglobin helps transport CO2 and buffer
the blood
• Hemoglobin helps buffer the pH of blood and
carries some CO2
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• Most CO2 in the blood
combines with water to
form carbonic acid
– The carbonic acid
breaks down to form
H+ ions and
bicarbonate ions
– These help buffer the
blood
TISSUE CELL
CO2 produced
INTERSTITIAL CO
2
FLUID
BLOOD
PLASMA
WITHIN
CAPILLARY
CO2
CO2
H2O
RED
BLOOD
CELL
H2CO3
Carbonic acid
HCO3–
+
Bicarbonate
HCO3–
Figure 22.11A
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Capillary
wall
H+
Hemoglobin
picks up
CO2 and H+
ALVEOLAR SPACE IN LUNG
• Most CO2 is
transported to the
lungs in the form of
bicarbonate ions
CO2
CO2
CO2
CO2
H2O
Hemoglobin
releases
CO2 and H+
H2CO3
HCO3–
HCO3–
Figure 22.11B
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+
H+
22.12 Connection: The human fetus exchanges
gases with the mother’s bloodstream
• A human fetus
depends on the
placenta for gas
exchange
Placenta, containing
maternal blood vessels
and fetal capillaries
Umbilical cord,
containing fetal
blood vessels
Amniotic
fluid
Uterus
Figure 22.12
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• A network of capillaries exchanges O2 and CO2
with maternal blood that carries gases to and
from the mother’s lungs
• At birth, increasing CO2 in the fetal blood
stimulates the fetus’s breathing control centers
to initiate breathing
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