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Gas Exchange: Respiration. Respiratory medium (air of water). O 2. CO 2. Respiratory surface. Organismal level. Circulatory system. Cellular level. Energy-rich molecules from food. ATP. Cellular respiration. Figure 42.19. Gas exchange occurs across specialized respiratory surfaces - PowerPoint PPT Presentation
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Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Gas Exchange: Respiration
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Gas exchange occurs across specialized respiratory surfaces
• Gas exchange
– Supplies oxygen for cellular respiration and disposes of carbon dioxide
Figure 42.19
Organismal level
Cellular level
Circulatory system
Cellular respiration ATPEnergy-richmoleculesfrom food
Respiratorysurface
Respiratorymedium(air of water)
O2 CO2
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Animals require large, moist respiratory surfaces for the adequate diffusion of respiratory gases
– Between their cells and the respiratory medium, either air or water
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• In mammals, air inhaled through the nostrils
– Passes through the pharynx into the trachea, bronchi, bronchioles, and dead-end alveoli, where gas exchange occurs
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Gas exchange: occurs in alveoli of lungs, diffusion of oxygen and carbon dioxide through capillaries
• Ventilation: bringing in fresh air into the alveoli (breathing)
• Cellular respiration: produces ATP for the cell, uses oxygen and produces carbon dioxide.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Mammalian Respiratory Systems: A Closer Look
• A system of branching ducts
– Conveys air to the lungsBranch from the pulmonary vein (oxygen-rich blood) Terminal bronchiole
Branch from thepulmonaryartery(oxygen-poor blood)
Alveoli
Colorized SEMSEM
50 µ
m
50 µ
m
Heart
Left lung
Nasalcavity
Pharynx
Larynx
Diaphragm
Bronchiole
Bronchus
Right lung
TracheaEsophagus
Figure 42.23
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Alveoli
• Very small but huge in numbers (large surface area for gas exchange)
• Made up of a single layer of thin cells
• Covered by a dense network of blood capillaries
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
How a Mammal Breathes
• Mammals ventilate their lungs by breathing
– By negative pressure breathing, which pulls air into the lungs
Air inhaled Air exhaled
INHALATIONDiaphragm contracts
(moves down)
EXHALATIONDiaphragm relaxes
(moves up)
Diaphragm
Lung
Rib cage expands asrib muscles contract
Rib cage gets smaller asrib muscles relax
Figure 42.24
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Inhalation:
• External intercostal muscles contract (moves rib cage up and out)
• Diaphragm contracts
• Increase in volume, drop in pressure (below atmospheric pressure)
• Air flows into lungs until pressure inside lungs rises to atmospheric pressure.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Exhalation
• Internal intercostal muscles contract (moves rib cage down and in)
• Abdominal muscles contract, pushing up diaphragm
• Decrease in volume, pressure rises above atmospheric pressure
• Air flows out of lungs until the pressure in lungs falls back to atmospheric pressure.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Why do we need a ventilation system???• Maintain the concentration gradients of gases
(oxygen/carbon dioxide) in the alveoli.
– Carbon dioxide needs to be low in alveoli so it moves into the alveoli from capillaries.
– Oxygen needs to be high in alveoli so it can move into capillaries.
– Ventilation makes this possible by getting rid of carbon dioxide and bringing in oxygen
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The Role of Partial Pressure Gradients
• Gases diffuse down pressure gradients
– In the lungs and other organs
• Diffusion of a gas
– Depends on differences in a quantity called partial pressure
• A gas always diffuses from a region of higher partial pressure
– To a region of lower partial pressure
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• In the lungs and in the tissues
– O2 and CO2 diffuse from where their partial pressures are higher to where they are lower
– RESPIRATION
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Inhaled air Exhaled air
160 0.2O2 CO2
O2 CO2
O2 CO2
O2 CO2 O2 CO2
O2 CO2 O2 CO2
O2 CO2
40 45
40 45
100 40
104 40
104 40
120 27
CO2O2
Alveolarepithelialcells
Pulmonaryarteries
Blood enteringalveolar
capillaries
Blood leavingtissue
capillaries
Blood enteringtissue
capillaries
Blood leaving
alveolar capillaries
CO2O2
Tissue capillaries
Heart
Alveolar capillaries
of lung
<40 >45
Tissue cells
Pulmonaryveins
Systemic arteriesSystemic
veinsO2CO2
O2
CO2
Alveolar spaces
12
43
Figure 42.27
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Respiratory Pigments
• Respiratory pigments
– Are proteins that transport oxygen
• Greatly increase the amount of oxygen that blood can carry
• The respiratory pigment of almost all vertebrates
– Is the protein hemoglobin, contained in the erythrocytes
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Like all respiratory pigments
– Hemoglobin must reversibly bind O2, loading O2 in the lungs and unloading it in other parts of the body
Heme group Iron atom
O2 loadedin lungs
O2 unloadedIn tissues
Polypeptide chain
O2
O2
Figure 42.28