Transcript Document

BIOLOGY
CONCEPTS & CONNECTIONS
Fourth Edition
Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor
CHAPTER 22
Respiration: The Exchange of
Gases
Modules 22.1 – 22.4
From PowerPoint® Lectures for Biology: Concepts & Connections
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
MECHANISMS OF GAS EXCHANGE
• Gas exchange / respiration - interchange of O2
and CO2 between organism and environment
• Gas exchange essential because energy
metabolism requires O2 and produces CO2
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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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• Some animals use entire skin as gas-exchange
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: extensions of body that absorb O2
dissolved in water
• In fish, gill filaments have numerous platelike
lamellae
– Lamellae: packed with blood vessels
– Are 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 opposite
direction to water flow
– Countercurrent
maintains diffusion
gradient that
maximizes
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 - easier to move than water
– But water loss from respiratory surfaces can be
problem
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• Insects: network of tracheal tubes carries out
gas exchange
– O2 diffuses from 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 nasal cavity
– Passes through pharynx -> larynx -> trachea
– Trachea -> two bronchi
– Each bronchus -> numerous bronchioles
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• Gas exchange in
the body
Figure 22.10A
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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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• Brionchioles end in clusters of
tiny sacs - alveoli
– Alveoli: respiratory surface of
lungs
– Oxygen diffuses
through thin
walls of
alveoli into
blood
Figure 22.6C
Oxygen-rich
blood
Oxygen-poor
blood
Bronchiole
Alveoli
Blood capillaries
Figure 22.6B
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22.8 Breathing ventilates the lungs
• Breathing: 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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• Bird: air sacs
– keep air flowing through lungs but 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: pons and medulla of
the brain
– Automatic controls based on need
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• When 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
• Hemoglobin: protein in red blood cells
– Carrie most of the oxygen in 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 pH of blood and
carries some CO2
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• Most CO2 in the blood
+ water  carbonic
acid (H2CO3)
– Carbonic acid breaks
down to form H+ ions
and bicarbonate ions
TISSUE CELL
CO2 produced
INTERSTITIAL CO
2
FLUID
BLOOD
PLASMA
WITHIN
CAPILLARY
CO2
Capillary
wall
CO2
H2O
– Help buffer blood
RED
BLOOD
CELL
H2CO3
Carbonic acid
HCO3–
+
Bicarbonate
HCO3–
Figure 22.11A
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H+
Hemoglobin
picks up
CO2 and H+
• Most CO2 transported
to lungs as bicarbonate
ions
ALVEOLAR SPACE IN LUNG
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
• Human fetus
depends on
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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• Network of capillaries exchanges O2 and CO2
with maternal blood that carries gases to and
from 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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