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Mechanics of Breathing (Pulmonary Ventilation)

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Presentation on theme: "Mechanics of Breathing (Pulmonary Ventilation)"— Presentation transcript:

1 Mechanics of Breathing (Pulmonary Ventilation)
Completely mechanical process Depends on volume changes in the thoracic cavity Volume changes lead to pressure changes, which lead to the flow of gases to equalize pressure Slide 13.21a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

2 Mechanics of Breathing (Pulmonary Ventilation)
Two phases Inspiration – flow of air into lung Expiration – air leaving lung Slide 13.21b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

3 Inspiration Diaphragm and intercostal muscles contract
The size of the thoracic cavity increases External air is pulled into the lungs due to an increase in intrapulmonary volume Slide 13.22a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

4 Inspiration Figure 13.7a Slide 13.22b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

5 Exhalation Largely a passive process which depends on natural lung elasticity As muscles relax, air is pushed out of the lungs Forced expiration can occur mostly by contracting internal intercostal muscles to depress the rib cage Slide 13.23a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

6 Exhalation Figure 13.7b Slide 13.23b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings


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