Chapter 48: Gas Exchange in Animals
CHAPTER 48
Gas Exchange in Animals
Chapter 48: Gas Exchange in Animals
Chapter 48: Gas Exchange in
Animals
Respiratory Gas Exchange
Respiratory Adaptations for Gas Exchange
Mammalian Lungs and Gas Exchange
Blood Transport of Respiratory Gases
Regulating Breathing to Supply O2
Chapter 48: Gas Exchange in Animals
Respiratory Gas Exchange
• Most cells require a constant supply of O2
and continuous removal of CO2.
• These respiratory gases exchange between
the body fluids of an animal and its
environment by diffusion.
3
Chapter 48: Gas Exchange in Animals
Respiratory Gas Exchange
• In aquatic animals, gas exchange is limited
by low diffusion rate and low O2 level in
water.
• As water temperature rises, aquatic animals
face a double bind in that O2 in water
decreases, but
• Their metabolism and work required to
move water over gas exchange surfaces
increases.
Review Figure 48.2
Chapter 48: Gas Exchange in Animals
figure 48-02.jpg
Figure 48.2
Figure 48.2
Chapter 48: Gas Exchange in Animals
Respiratory Adaptations for
Gas Exchange
• The evolution of large animals with high
metabolic rates required adaptations to
maximize respiratory gas diffusion rates:
• Increasing surface areas
• maximizing partial pressure gradients
• decreasing their thickness
• ventilating the outer surface with gases
• perfusing the inner surface with blood.
Review Figure 48.4
6
Chapter 48: Gas Exchange in Animals
figure 48-04.jpg
Figure 48.4
Figure 48.4
Chapter 48: Gas Exchange in Animals
Respiratory Adaptations for
Gas Exchange
• Insects distribute air throughout their bodies
in a system of tracheae, tracheoles, and air
capillaries.
Review Figure 48.5
8
Chapter 48: Gas Exchange in Animals
figure 48-05.jpg
Figure
48.5
Figure 48.5
Chapter 48: Gas Exchange in Animals
Respiratory Adaptations for
Gas Exchange
• Fish have maximized gas exchange rates by
having large gas exchange surface areas
ventilated continuously and unidirectionally
with fresh water.
• Countercurrent blood flow helps increase
gas exchange efficiency.
Review Figures 48.6, 48.7
10
Chapter 48: Gas Exchange in Animals
figure 48-06.jpg
Figure
48.6
Figure 48.6
Chapter 48: Gas Exchange in Animals
figure 48-07.jpg
Figure
48.7
Figure 48.7
Chapter 48: Gas Exchange in Animals
Respiratory Adaptations for
Gas Exchange
• The gas exchange system of birds includes
air sacs that communicate with the lungs
but are not used for gas exchange.
• Air flows unidirectionally through bird lungs
in parabronchi.
• Gases are exchanged in air capillaries
running between parabronchi.
Review Figures 48.8, 48.9
13
Chapter 48: Gas Exchange in Animals
figure 48-08.jpg
Figure
48.8
Figure 48.8
Chapter 48: Gas Exchange in Animals
figure 48-09.jpg
Figure
48.9
Figure 48.9
Chapter 48: Gas Exchange in Animals
Respiratory Adaptations for
Gas Exchange
• Each breath of air remains in the bird
respiratory system for two breathing cycles.
• The air sacs work as bellows to supply the
air capillaries with a continuous,
unidirectional flow of fresh air.
Review Figure 48.10
16
Chapter 48: Gas Exchange in Animals
Figure
48.10 –
Part 1
Figure 48.10 – Part 1
figure 48-10a.jpg
Chapter 48: Gas Exchange in Animals
Figure 48.10
– Part 2
Figure 48.10 – Part 2
figure 48-10b.jpg
Chapter 48: Gas Exchange in Animals
Respiratory Adaptations for
Gas Exchange
• Breathing in vertebrates other than birds is
tidal, thus less efficient than gas exchange
in fishes or birds.
• Even though the volume of air exchanged
with each breath can vary considerably,
inhaled air is always mixed with stale air.
Review Figure 48.11
19
Chapter 48: Gas Exchange in Animals
figure 48-11.jpg
Figure
48.11
Figure 48.11
Chapter 48: Gas Exchange in Animals
Mammalian Lungs and Gas
Exchange
• In mammalian lungs, the gas exchange
surface area provided by the millions of
alveoli is enormous, and
• The diffusion path length between the air
and perfusing blood is very short.
Review Figure 48.12
21
Chapter 48: Gas Exchange in Animals
Figure
48.12 –
Part 1
Figure 48.12 – Part 1
figure 48-12a.jpg
Chapter 48: Gas Exchange in Animals
Figure 48.12
– Part 2
Figure 48.12 – Part 2
figure 48-12b.jpg
Chapter 48: Gas Exchange in Animals
Mammalian Lungs and Gas
Exchange
• Surface tension in the alveoli would make
their inflation difficult if the lungs did not
produce surfactant.
24
Chapter 48: Gas Exchange in Animals
Mammalian Lungs and Gas
Exchange
• Inhalation occurs when contractions of the
diaphragm and intercostal muscles create
negative pressure in the thoracic cavity.
• Relaxation of the diaphragm and some
intercostal muscles and contraction of other
intercostal muscles increases pressure in the
thoracic cavity causing exhalation.
Review Figure 48.13
25
Chapter 48: Gas Exchange in Animals
figure 48-13.jpg
Figure
48.13
Figure 48.13
Chapter 48: Gas Exchange in Animals
Blood Transport of Respiratory Gases
• Oxygen is reversibly bound to hemoglobin in red
blood cells.
• Each hemoglobin molecule can carry four O2
molecules maximum.
• Because of positive cooperativity, affinity of
hemoglobin for O2 depends on the <PO2 to which
the hemoglobin is exposed.
• Therefore, hemoglobin gives up O2 in metabolically
active tissues and picks it up as it flows through
respiratory exchange structures.
Review Figure 48.14
27
Chapter 48: Gas Exchange in Animals
figure 48-14.jpg
Figure
48.14
Figure 48.14
Chapter 48: Gas Exchange in Animals
Blood Transport of
Respiratory Gases
• Myoglobin has a very high affinity for
oxygen and serves as an oxygen reserve in
muscle.
29
Chapter 48: Gas Exchange in Animals
Blood Transport of
Respiratory Gases
• Fetal hemoglobin has a higher affinity for O2
than does maternal hemoglobin, allowing
fetal blood to pick up O2 from maternal
blood in the placenta.
Review Figure 48.15
30
Chapter 48: Gas Exchange in Animals
figure 48-15.jpg
Figure
48.15
Figure 48.15
Chapter 48: Gas Exchange in Animals
Blood Transport of
Respiratory Gases
• The affinity of hemoglobin for oxygen is
decreased by the presence of hydrogen ions
or 2,3 diphosphoglyceric acid.
Review Figure 48.16
32
Chapter 48: Gas Exchange in Animals
figure 48-16.jpg
Figure
48.16
Figure 48.16
Chapter 48: Gas Exchange in Animals
Blood Transport of
Respiratory Gases
• Carbon dioxide is carried in the blood
principally as bicarbonate ions.
Review Figure 48.17
34
Chapter 48: Gas Exchange in Animals
Figure
48.17 –
Part 1
Figure 48.17 – Part 1
figure 48-17a.jpg
Chapter 48: Gas Exchange in Animals
Figure
48.17 –
Part 2
Figure 48.17 – Part 2
figure 48-17b.jpg
Chapter 48: Gas Exchange in Animals
Regulating Breathing to
Supply O2
• Breathing rhythm is an autonomic function
generated by neurons in the medulla of the
brain stem and modulated by higher brain
centers.
Review Figure 48.18
37
Chapter 48: Gas Exchange in Animals
figure 48-18.jpg
Figure
48.18
Figure 48.18
Chapter 48: Gas Exchange in Animals
Regulating Breathing to
Supply O2
• The most important feedback stimulus for
breathing is level of CO2 in the blood.
Review Figure 48.19
39
Chapter 48: Gas Exchange in Animals
figure 48-19.jpg
Figure
48.19
Figure 48.19
Chapter 48: Gas Exchange in Animals
Regulating Breathing to
Supply O2
• Breathing rhythm is sensitive to feedback
from chemoreceptors on the ventral surface
of the brain stem and in the carotid and
aortic bodies on the large vessels leaving
the heart.
Review Figure 48.20
41
Chapter 48: Gas Exchange in Animals
figure 48-20.jpg
Figure
48.20
Figure 48.20