1. Mechanics of Breathing
Chapter 17
Mechanics of Breathing

2. The respiratory system Gas laws Ventilation
About this Chapter
The respiratory system
Gas laws
Ventilation

3. Homeostatic regulation of body pH
Respiratory System
Functions
External Respiration
Exchange of gases between the atmosphere and the blood
Homeostatic regulation of body pH
Protection from inhaled pathogens and irritating substances
Vocalization

4. Principles of Bulk Flow Flow from regions of higher to lower pressure
Respiratory System
Principles of Bulk Flow
Flow from regions of higher to lower pressure
Muscular pump creates pressure gradients
Resistance to flow
Diameter of tubes

5. Transport of gases in the blood
Respiratory System
CO2 O2
Alveoli of lungs
Airways
Pulmonary circulation
Cellular respiration
ATP
Nutrients
Cells
Systemic circulation
Exchange I: atmosphere to lung (ventilation)
Transport of gases in the blood
Exchange III: blood to cells
Exchange II: lung to blood
Overview of external and cellular respiration
Figure 17-1

6. Respiratory System Components
Conducting system
Alveoli
Bones and muscle of thorax

7. Upper respiratory system Lower respiratory system
ANATOMY SUMMARY
THE LUNGS AND THORACIC CAVITY
Pharynx
Nasal cavity
Vocal cords
Upper respiratory system
Tongue
Esophagus
Larynx
Trachea
Lower respiratory system
Right lung
Left lung
Diaphragm
Left bronchus
Right bronchus
(a) The respiratory system
Figure 17-2a

8. Muscles Used for Ventilation
Sternocleido- mastoids
Scalenes
Internal intercostals
External intercostals
Diaphragm
Abdominal muscles
Muscles of inspiration
Muscles of expiration
(b) Muscles used for ventilation
Figure 17-2b

9. The Respiratory System
Air space of lung
Air-filled balloon
Pleural fluid
Pleural membrane
Fluid-filled balloon
Figure 17-3

10. Branching of Airways Figure 17-2e Larynx Trachea Cartilage ring
ANATOMY SUMMARY
THE LUNGS AND THORACIC CAVITY
Larynx
Trachea
Cartilage ring
Left primary bronchus
Secondary bronchus
Bronchiole
Alveoli
(e) Branching of airways
Figure 17-2e

11. Branching of the Airways
Figure 17-4

12. Warming air to body temperature Adding water vapor
Conditioning Air
Warming air to body temperature
Adding water vapor
Filtering out foreign material

13. Ciliated Respiratory Epithelium
Cilia move mucus to pharynx
Dust particle
Mucus layer traps inhaled particles.
inhaled particles.
Watery saline layer allows cilia to push mucus toward pharynx.
Cilia
Goblet cell secretes mucus.
Nucleus of columnar epithelial cell
Basement membrane
Ciliated epithelium of the trachea
Figure 17-5

14. Alveolar Structure – Note cell types of alveoli
Figure 17-2g

15. Pulmonary Circulation
Right ventricle  pulmonary trunk  lungs  pulmonary veins  left atrium
Note oxygenation

16. Anatomy Review
PLAY
Interactive Physiology® Animation: Respiratory System: Anatomy Review

17. Gas Laws
Table 17-1

18. Pgas = Patm  % of gas in atmosphere
Gas Laws
Pgas = Patm  % of gas in atmosphere
Table 17-2

19. Gases move from areas of high pressure to areas of low pressure
Boyle’s Law
Gases move from areas of high pressure to areas of low pressure
Figure 17-6

20. Spirometer Figure 17-7 Bell Inspiration Expiration Inspiration
Air
0.5
Volume (L)
Water
Time
Figure 17-7

21. Lung Volumes and Capacities
Figure 17-8

22. Alveolar pressure or intrapleural pressure can be measured
Air Flow
Flow  P/R
Alveolar pressure or intrapleural pressure can be measured
Single respiratory cycle consists of one inspiration followed by one expiration

23. Movement of the Diaphragm
Figure 17-9a

24. Movement of the Diaphragm
Figure 17-9b

25. Movement of the Diaphragm
Figure 17-9c

26. Dimensions of the Thoracic Cavity During Inspiration
Figure 17-10a

27. Dimensions of the Thoracic Cavity During Inspiration
Figure 17-10b

28. Pressure Changes During Quiet Breathing
Inspiration
Expiration
Inspiration
Expiration +2
Alveolar pressure (mm Hg) A4
Trachea +1 A1 A3 A5
Bronchi –1 A2 –2
Lung
Intrapleural pressure (mm Hg) B3 B1 –3 –4
Diaphragm –5 –6
Right pleural cavity
Left pleural cavity B2
750
Volume of air moved (mL)
500 C2
250 C3 C1 1 2 3 4 5 6 7 8
Time (sec)
Figure 17-11

29. Subatmospheric Pressure in the Pleural Cavity
Ribs
P = –3 mm Hg Intrapleural pressure is subatmospheric.
Intrapleural space
Pleural membranes
Diaphragm
Elastic recoil of the chest wall tries to pull the chest wall outward.
Elastic recoil of lung creates an inward pull.
(a) Normal lung at rest
Figure 17-12a

30. Subatmospheric Pressure in the Pleural Cavity
Pneumothorax results in collapsed lung that cannot function normally
P = Patm
Knife
Lung collapses to unstretched size
Air
Intrapleural space
Pleural membranes
The rib cage expands slightly.
If the sealed pleural cavity is opened to the atmosphere, air flows in.
(b) Pneumothorax
Figure 17-12b

31. Compliance and Elastance
Compliance: ability to stretch
High compliance
Stretches easily
Low compliance
Requires more force
Restrictive lung diseases
Fibrotic lung diseases
Inadequate surfactant production
Elastance: returning to its resting volume when stretching force is released

32. Law of LaPlace
Surface tension is created by the thin fluid layer between alveolar cells and the air
Figure 17-13

33. More concentrated in smaller alveoli
Surfactant
More concentrated in smaller alveoli
Mixture containing proteins and phospholipids
Newborn respiratory distress syndrome
Premature babies
Inadequate surfactant concentrations

34. Air Flow
Table 17-3

35. Pulmonary Ventilation
PLAY
Interactive Physiology® Animation: Respiratory System: Pulmonary Ventilation

36. Total pulmonary ventilation = ventilation rate  tidal volume
Total pulmonary ventilation is greater than alveolar ventilation because of dead space
Total pulmonary ventilation = ventilation rate  tidal volume

37. Dead space filled with fresh air Dead space filled with stale air
Ventilation
Dead space filled with fresh air
The first exhaled air comes out of the dead space. Only 350 mL leaves the alveoli.
150 mL 1
End of inspiration 1
2700 mL
Atmospheric
air 2
Exhale 500 mL (tidal volume)
150
350 3
At the end of expiration, the dead space is filled with “stale” air from alveoli.
Dead space is filled with fresh air. 2
150 mL
150
RESPIRATORY CYCLE IN ADULT
Only 350 mL of fresh air reaches alveoli
350 4
Inhale 500 mL of fresh air (tidal volume).
2200 mL
150
2200 mL
The first 150 mL of air into the alveoli is stale air from the dead space. 4
Dead space filled with stale air
KEY
150 mL P O2 =
150 mm Hg (fresh air) P O2 ~
100 mm Hg (stale air)
2200 mL 3
Figure 17-14

38. Ventilation
Alveolar ventilation = ventilation rate  (tidal volume – dead space volume)
Table 17-4

39. Ventilation
Table 17-5

40. Ventilation
Table 17-6

41. Ventilation
As alveolar ventilation increases, alveolar PO2 increases and PCO2 decreases
Figure 17-15

42. Ventilation
Table 17-7

43. Local control mechanisms attempt to match ventilation and perfusion
Figure 17-16a

44. Ventilation
Figure 17-16b

45. Ventilation
Figure 17-16c

46. Auscultation = diagnostic technique Obstructive lung diseases
Ventilation
Auscultation = diagnostic technique
Obstructive lung diseases
Asthma
Emphysema
Chronic bronchitis

47. Gas Laws: Dalton’s law and Boyle’s law
Summary
Respiratory system
Cellular respiration, external respiration, respiratory system, upper respiratory tract, pharynx, and larynx
Lower respiratory tract, trachea, bronchi, bronchioles, alveoli, Type I and Type II alveolar cells
Diaphragm, intercostal muscles, lung, pleural sac, and pleural fluid
Gas Laws: Dalton’s law and Boyle’s law

48. Summary
Ventilation
Tidal volume, vital capacity, residual volume, and respiratory cycle
Alveolar pressure, active expiration, intrapleural pressures, compliance, elastance, surfactant, bronchoconstriction, and bronchodilation
Total pulmonary ventilation, alveolar ventilation, hyperventilation, and hypoventilation