Biology, Seventh Edition
Solomon • Berg • Martin
Chapter 44
Gas Exchange
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 44 Gas Exchange
• Respiration
• The exchange of gases between
an organism and its environment
• Organismic respiration
–Takes place in animals
–O2 taken up and CO2 excreted
• Aerobic cellular respiration
–Takes place in mitochondria
–O2 is necessary for citric acid cycle
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Biology, Seventh Edition
CHAPTER 44 Gas Exchange
• Simple diffusion
• Passive movement of particles
from a region of higher
concentration to a region of lower
• Provides gas exchange for small,
aquatic organisms such as
sponges, hydras, and flatworms
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Biology, Seventh Edition
CHAPTER 44 Gas Exchange
• Comparison of gas exchange in
air and water
• Air
–Contains a higher concentration of
molecular oxygen than water
–Oxygen diffuses more rapidly
through air than water
–Less energy needed to move air
over gas exchange surface
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Biology, Seventh Edition
CHAPTER 44 Gas Exchange
• Adaptations for gas exchange
• Body surface
–Small aquatic animals exchange
gases by diffusion, requiring no
specialized respiratory structures
–Some invertebrates, including most
annelids, and many amphibians
exchanges gases across the body
surface
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Biology, Seventh Edition
CHAPTER 44 Gas Exchange
Gas exchange across body surface
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Biology, Seventh Edition
CHAPTER 44 Gas Exchange
• Adaptations for gas exchange,
cont’d
• Trachae
–In insects and some other
anthropods, air enters trachae
through openings called spiracles
–Trachae branch and extend to all
regions of the body
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Biology, Seventh Edition
CHAPTER 44 Gas Exchange
Gas exchange across tracheal tubes
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Biology, Seventh Edition
CHAPTER 44 Gas Exchange
• Adaptations for gas exchange,
cont.
• Gills
–Moist, thin projections of the body
surface found mainly in aquatic
animals
–Countercurrent exchange system
maximizes O2 into the blood and
CO2 out of the blood
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Biology, Seventh Edition
CHAPTER 44 Gas Exchange
Gas exchange across gills
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Biology, Seventh Edition
CHAPTER 44 Gas Exchange
• Adaptations for gas exchange,
cont.
• Lungs
–Terrestrial vertebrates have lungs
and some means of ventilating
them
–Lungs are respiratory structures
that develop as ingrowths of body
surface or from wall of a body cavity
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Biology, Seventh Edition
CHAPTER 44 Gas Exchange
Gas exchange across lungs
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Biology, Seventh Edition
CHAPTER 44 Gas Exchange
Comparison
of vertebrate
lungs
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Biology, Seventh Edition
CHAPTER 44 Gas Exchange
How bird lungs function
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Biology, Seventh Edition
CHAPTER 44 Gas Exchange
• Mammalian respiratory system
• Includes the lungs and airways
• Lung occupies pleural cavity and is
covered with a pleural membrane
• Breath of air passes in sequence
–Nostrils, nasal cavities, pharynx,
larynx, trachea, bronchi, bronchioles,
and alveoli
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Biology, Seventh Edition
CHAPTER 44 Gas Exchange
The human respiratory system
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Biology, Seventh Edition
CHAPTER 44 Gas Exchange
Structure of alveoli
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Biology, Seventh Edition
CHAPTER 44 Gas Exchange
• Mechanics of breathing
• Diaphragm contracts and chest
cavity expands
• Respiratory centers in the medulla
and pons regulate respiration
–Stimulated by chemoreceptors
–An increase in hydrogen ions and low
oxygen concentration
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Biology, Seventh Edition
CHAPTER 44 Gas Exchange
Mechanics of breathing
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Biology, Seventh Edition
CHAPTER 44 Gas Exchange
• Role of hemoglobin in oxygen
transport
• Respiratory pigment in vertebrate
blood
• Almost 99% of the O2 in human
blood is transported as
oxyhemoglobin (HbO2 )
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Biology, Seventh Edition
CHAPTER 44 Gas Exchange
Gas exchange in the lungs and tissues
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Biology, Seventh Edition
CHAPTER 44 Gas Exchange
• Oxygen-carrying capacity
• Maximum amount of O2 that can be
transported by hemoglobin
• Oxygen content
• Actual amount of O2 bound to
hemoglobin
• Percent oxygen saturation
• Ratio of O2 content to O2 carrying
capacity
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Biology, Seventh Edition
CHAPTER 44 Gas Exchange
• Oxygen-hemoglobin dissociation
curve
• Shows that as O2 concentration
increases, there is progressive
increase in hemoglobin that
combines with O2
• Bohr effect
• Oxyhemoglobin dissociates more
readily as CO2 increases
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Biology, Seventh Edition
CHAPTER 44 Gas Exchange
Oxygen-hemoglobin dissociation curves
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Biology, Seventh Edition
CHAPTER 44 Gas Exchange
Carbon
dioxide
transport
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Biology, Seventh Edition
CHAPTER 44 Gas Exchange
• Hyperventilation
• Reduces the concentration of CO2
in the alveolar air and the blood
• Decompression in divers
• Rapid decrease in barometric
pressure can cause decompression
sickness
• Diving mammals have high
concentrations of myoglobin
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Biology, Seventh Edition
CHAPTER 44 Gas Exchange
Deep diver
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Biology, Seventh Edition
CHAPTER 44 Gas Exchange
• Affects of pollution on the
respiratory system
• Ciliated mucous lining traps inhaled
particles
• Inhaling polluted air results in
bronchial constriction
–Increased mucous secretion
–Damage to ciliated cells
–Coughing
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