1. Mechanics of Breathing
Chapter 17
Mechanics of Breathing

2. About this Chapter Structure and function of the respiratory pumps
How gasses are exchanged with blood
The role of pressures and surfactants in rate of exchange
How respiration is regulated

3. Respiratory System: Overview
Lungs: exchange surface
75 m2
Thin walled
Moist
Ribs & skin protect
Diaphragm & ribs pump air
PLAY
Animation: Respiratory System: Anatomy Review

4. Respiratory System: Overview
Figure 17-2 b: Anatomy Summary

5. Functions of the Respiratory System: Overview
Exchange O2
Air to blood
Blood to cells
Exchange CO2
Cells to blood
Blood to air
Regulate blood pH
Vocalizations
Protect alveoli
Figure 17-1: Overview of external and cellular respiration

6. The Airways: Conduction of Air from Outside to Alveoli
Filter, warm & moisten air
Nose, (mouth), trachea, bronchi & bronchioles
Huge increase in cross sectional area
Figure 17-4: Branching of the airways

7. Key Gas Laws Reviewed Gas is compressible & flow  with  resistance
Air is a mix of gasses, each diffuses independently

8. Key Gas Laws Reviewed Solubility of a gas depends on:
Partial pressure of that gas (example: O2 =156 mmHg)
Temperature
Solubility in a particular solvent
Water: solvent for life
O2 into water: 0.1 m moles/L (poor)
CO2 into water: 3.0 m mole/L (good)
PLAY
Animation: Respiratory System: Pulmonary Ventilation

9. Ventilation: The Pumps
Inspiration
Expiration
Diaphragm
Low energy pump
Concavity – flattens
Thorax: ribs & muscles
Pleura: double membrane
Vacuum seal
Fluid-lubrication

10. Ventilation: The Pumps
Figure a: Surfactant reduces surface tension
PLAY
Animation: Respiratory System: Pulmonary Ventilation

11. Respiratory Damage & Diseases
Pneumothorax ("collapsed lung")
Fibrotic Lung Disease
Emphysema
Asthma
NRDS

12. Respiratory Damage & Diseases
Figure 17-11b: Surfactant reduces surface tension

13. Factors Affecting Ventilation
Airway Resistance
Diameter
Mucous blockage
Bronchoconstriction
Bronchodilation
Alveolar compliance
Surfactants
Surface tension
Alveolar elasticity
Figure 17-2e: Anatomy Summary

14. Lung Volumes: Spirometer Measurements
Tidal volume:
Inspiratory reserve
Expiratory reserve
Residual
Vital capacity

15. Lung Volumes: Spirometer Measurements
Figure 17-12: The recording spirometer

16. Lung Volumes: Spirometer Measurements
Figure 17-14: Total pulmonary and alveolar ventilation

17. Efficiency of Breathing: Normal & High Demand
Total Pulmonary Ventilation
(rate X tidal vol about 6 L/min)
Alveolar ventilation
(– dead air space – 4.5 L/min)
Little variation [O2] & [CO2]
Exercise- High Demand
 Depth of breathing
Use inspiratory reserve

18. Efficiency of Breathing: Normal & High Demand
Figure 17-14: Total pulmonary and alveolar ventilation

19. Efficiency of Breathing: Normal & High Demand
Figure 17-2 g: Anatomy Summary

20. Gas Exchange in the Alveoli
Thin cells: exchange
Surfactant cells
Elastic fibers
Recoil
Push air out
Thin basement membrane
Capillaries cover 90% of surface

21. Gas Exchange in the Alveoli
Figure 17-2 h : Anatomy Summary

22. Gas Exchange in the Alveoli
Figure 17-6: Ciliated respiratory epithelium

23. Matching Ventilation with Alveolar Blood Flow (Perfusion)
Mostly local regulation
Low [O2] in alveoli  vasoconstriction of arteriole
Reduced blood flow at rest
(lung apex )
saves energy
High blood [CO2]  bronchodilation

24. Matching Ventilation with Alveolar Blood Flow (Perfusion)
Figure 17-6: Ciliated respiratory epithelium

25. Summary Diaphragm & rib cage are pumps for inspiration
Alveolar surface exchanges O2 & CO2 with blood
The gasses in air act independently & move down a pressure gradient
Airway resistance can limit ventilation efficiency
Typically ventilation matches blood perfusion via local regulators of vasodilation & bronchodilation