1. Respiratory Physiology I
13b

2. Gas Exchange Gas crosses the respiratory membrane by diffusion
Oxygen enters the blood
Carbon dioxide enters the alveoli
Macrophages add protection
Surfactant coats gas-exposed alveolar surfaces
Slide 13.19
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3. A&P Revealed
Diffusion Across Respiratory Membrane

4. Events of Respiration
Pulmonary ventilation – moving air in and out of the lungs
External respiration – gas exchange between pulmonary blood and alveoli
Respiratory gas transport – transport of oxygen and carbon dioxide via the bloodstream
Internal respiration – gas exchange between blood and tissue cells in systemic capillaries
Slide 13.20a
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5. Quick Quiz Where in the body does Pulmonary Ventilation occur?
Why is the gas exchange at the alveoli called “external” while the gas exchange at the body tissues is called “internal”?

6. 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
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7. Mechanics of Breathing (Pulmonary Ventilation)
Two phases
Inspiration – flow of air into lung
Expiration – air leaving lung
Slide 13.21b
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8. Inspiration Breathing IN Diaphragm and intercostal muscles contract
Thoracic cavity size increases
External air is pulled into the lungs due to an increase in intrapulmonary volume
Slide 13.22a
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9. Inspiration Slide 13.22b Figure 13.7a
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10. Expiration Breathing OUT
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
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11. Expiration Slide 13.23b Figure 13.7b
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12. A&P Revealed
Thoracic Cavity Dimensional Changes

13. Quick Quiz Describe the process of Inspiration
Describe the process of expiration

14. Nonrespiratory Air Movements
Can be caused by reflexes or voluntary actions
Examples
Cough and sneeze – clears lungs of debris
Laughing
Crying
Yawn
Hiccup
Slide 13.25
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15. Respiratory Volumes and Capacities
Many factors that affect respiratory capacity
A person’s size
Sex
Age
Physical condition
Slide 13.26
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16. Respiratory Volumes and Capacities
Tidal Volume (TV)
The amount of air moved with each normal breath
Typically about 500ml of air in adults
Slide 13.26
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17. Respiratory Volumes and Capacities
Inspiratory reserve volume (IRV)
Amount of air that can be taken in forcibly over the tidal volume
Usually between 2100 and 3200 ml
Expiratory reserve volume (ERV)
Amount of air that can be forcibly exhaled
Approximately 1200 ml
Slide 13.27a
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18. Respiratory Volumes and Capacities
Residual volume
Air remaining in lung after expiration
About 1200 ml
Slide 13.27b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

19. Respiratory Volumes and Capacities
Vital capacity
The total amount of exchangeable air
Vital capacity = TV + IRV + ERV
Dead Space Volume
Air that remains in conducting zone and never reaches alveoli
About 150 ml
Slide 13.28
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20. Respiratory Volumes and Capacities
Functional volume
Air that actually reaches the respiratory zone
Usually about 350 ml
Respiratory capacities are measured with a spirometer
Slide 13.29
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21. Respiratory Capacities
Figure 13.9
Slide 13.30
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22. Respiratory Sounds Sounds are monitored with a stethoscope
Bronchial sounds
produced by air rushing through trachea and bronchi
Vesicular breathing sounds
soft sounds of air filling alveoli
Slide 13.31
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23. Quick Quiz Name 2 factors that can affect respiratory capacity
What is Tidal Volume?
What is Vital Capacity?