Chapter 34: Part 2
(Sections 34.5-34.7)
http://www.youtube.com/watch?v=hc1YtXc_84A
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
• Partial pressure
• For example, the atmosphere is ___ O2, by
volume, so the PO2 is ____  the atmospheric
pressure
• Gasses ALWAYS undergo net diffusion
Figure 34.17
Coelom
Gills
Parapodium (functions as gill)
(a) Marine worm
Tube foot
(b) Sea star
Importance of Gills
4
Figure 34.18
O2-poor blood
Gill
arch
Lamella
O2-rich blood
Blood
vessels
Gill arch
Water
Operculum
flow
Water flow
Blood flow
Countercurrent exchange
PO2 (mm Hg) in water
Gill filaments
Net
diffusion
of O2
150 120 90 60
30
140 110 80 50
30
PO2 (mm Hg)
in blood
Concurrent vs. Countercurrent Exchange
Tracheoles Mitochondria
Muscle fiber
2.5 m
Figure 34.19
Tracheae
Air sacs
Body
cell
Tracheole
Air
sac
Trachea
External opening
Air
Respiration in Air-Breathing Animals
• Gills replaced in terrestrial animals because:
1.
2.
• Two main terrestrial respiratory organs:
Amphibian Lungs
9
Bird Lungs
http://bcs.whfreeman.com/the
lifewire/content/chp48/48020
01.html
10
Figure 34.20
http://vimeo.com/25969150
Branch of
pulmonary vein
(oxygen-rich
blood)
Branch of pulmonary
artery (oxygen-poor
blood)
Terminal
bronchiole
Nasal
cavity
Pharynx
Left
lung
Larynx
(Esophagus)
Alveoli
Trachea
Right lung
Capillaries
50 m
Bronchus
Bronchiole
Diaphragm
(Heart)
Dense capillary bed
enveloping alveoli
(SEM)
Alveoli: Up Close
http://highered.mcgrawhill.com/sites/0072507470/student_view0/chapter23/animation__gas_excha
nge_during_respiration.html
Concept 34.6: Breathing ventilates the lungs
• Breathing is defined as:
• Breathing Measurements
– Tidal Volume –
– Vital Capacity –
– Residual Volume– Hypoventilating –
– Hyperventilating -
Figure 34.22
Rib cage
expands as
rib muscles
contract.
Air
inhaled.
Rib cage gets
smaller as
rib muscles
relax.
Air
exhaled.
Lung
Diaphragm
1 Inhalation:
Diaphragm contracts
(moves down).
2 Exhalation:
Diaphragm relaxes
(moves up).
http://highered.mcgrawhill.com/sites/0072507470/student_view0/chapter23/animation__alveolar_pressure_
changes_during_inspiration_and_expiration.html
How is breathing regulated in our bodies?
•In our brains we have a Respiratory Control Center (medulla)
•Controls our diaphragm/external intercostals
•HOW?
•NO SIGNAL=
•Breathing is USUALLY automatic
•Need to maintain a “normal” range of O2 and CO2 levels
•Body needs to be aware of PCO2 levels and PO2 levels
•What happens when you hold your breath or try to hold
your breath for an extended period of time?
Figure 34.23-4
Homeostasis:
Blood pH of about 7.4
CO2 level
decreases.
Response:
Signals from
medulla to rib
muscles and
diaphragm
increase rate
and depth of
ventilation.
Stimulus:
Rising level of CO2
in tissues lowers
blood pH.
Carotid
arteries
Sensor/control
center:
Cerebrospinal
fluid
Medulla
oblongata
Aorta
17
Concept 34.7: Adaptations for gas exchange
include pigments that bind and transport gases
• 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
http://highered.mcgrawhill.com/sites/0072507470/student_view0/chapter23/animation__changes_in_the
_partial_pressures_of_oxygen_and_carbon_dioxide.html
Figure 34.24
120 27
Inhaled air
Exhaled air
160 0.2
O2 CO2
O2 CO2
Alveolar
epithelial
cells
CO2
O2
Alveolar
spaces
Alveolar
capillaries
Pulmonary
veins
Pulmonary
arteries
40 45
104 40
O2 CO2
O2 CO2
Systemic
veins
Systemic
arteries
Systemic
capillaries
Heart
CO2
O2
<40 >45
O2 CO2
Body tissue
cells
Gas Exchange in Lungs
20
100
O2 unloaded
to tissues
at rest
80
O2 unloaded
to tissues
during exercise
60
40
20
0
0
20
Tissues during
exercise
40
60
Tissues
at rest
PO2 (mm Hg)
100
80
Lungs
(a) PO2 and hemoglobin dissociation
at pH 7.4
O2 saturation of hemoglobin (%)
O2 saturation of hemoglobin (%)
Figure 34.25
100
pH 7.4
80
pH 7.2
Hemoglobin
retains less
O2 at lower pH
(higher CO2
concentration
60
40
20
0
0
20
40
60
80
PO2 (mm Hg)
(b) pH and hemoglobin dissociation
100
Carbon Dioxide Transport
• About 8% of CO2 in blood is:
• About 20% of CO2 in blood is:
• Remaining 72% of CO2: