1. The Respiratory System: Pulmonary Ventilation
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2. Chapter Outline Overview of Respiratory Function
Anatomy of the Respiratory System
Forces for Pulmonary Ventilation
Factors Affecting Pulmonary Ventilation
Clinical Significance of Respiratory Volumes and Air Flows
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3. I. Overview of Respiratory Function
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4. Overview of Respiration
Internal respiration
Oxidative phosphorylation
External respiration
Exchange of oxygen and carbon dioxide between atmosphere and body tissues
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5. External Respiration Pulmonary ventilation
Exchange between lungs and blood
Transportation in blood
Exchange between blood and body tissues
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6. External Respiration: Ventilation and Exchange Between Lungs and Blood
Figure 17.1
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7. External Respiration: Transport in Blood
Figure 17.1
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8. External Respiration: Exchange Between Blood and Tissue
Figure 17.1
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9. Internal Respiration Figure 17.1
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10. II. Anatomy of the Respiratory System
Upper Airways
Respiratory Tract
Structures of the Thoracic Cavity
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11. Air passages of the head and neck
Upper Airways
Air passages of the head and neck
Nasal cavity
Oral cavity
Pharynx
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12. Upper Airways
Figure 17.2
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13. Airways from pharynx to lungs
Respiratory Tract
Airways from pharynx to lungs
Larynx
Conducting zone
Respiratory zone
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14. Respiratory Tract Figure 17.2
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15. Structures of the Conducting Zone
Trachea
Bronchi
Secondary bronchi
Right side - 3 (to 3 lobes of right lung)
Left side - 2 (to 2 lobes of left lung)
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16. Structures of the Conducting Zone
Tertiary,...Bronchi
20-23 orders of branching
Bronchioles
Less than 1 mm diameter
Terminal bronchioles
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17. Functions of the Conducting Zone
Air passageway
150 mL volume = dead space volume
Increase air temperature to body temperature
Humidify air
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18. Epithelium of the Conducting Zone
Goblet cells – secret mucus
Ciliated cells – cilia move particles toward mouth
Mucus escalator
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19. Anatomical Features of the Conducting Zone
Figure 17.3
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20. Photomicrograph of Tracheal Epithelium
Figure 17.4a
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21. Structures of the Respiratory Zone
Respiratory bronchioles
Alveolar ducts
Alveoli
Alveolar sacs
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22. Function of the Respiratory Zone
Exchange of gases between air and blood by diffusion
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23. Epithelium of the Respiratory Zone
Respiratory membrane
Epithelial cells of alveoli
Endothelial cells of capillary
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24. Anatomical Features of the Respiratory Zone
Figure 17.3
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25. Photomicrograph of Respiratory Bronchioles and Alveoli
Figure 17.4b
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26. Respiratory Zone Figure 17.5a, b
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27. Anatomy of Alveoli Figure 17.5c
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28. Alveoli Alveoli = site of gas exchange
300 million alveoli/lung (tennis court size)
Rich blood supply- capillaries form sheet over alveoli
Alveolar pores
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29. Alveoli Type I alveolar cells – make up wall of alveoli
Single layer epithelial cells
Type II alveolar cells – secrete surfactant
Alveolar macrophages
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30. The Respiratory Membrane
Figure 17.5d
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31. Respiratory Membrane Barrier for diffusion 0.2 microns thick
Type 1 cells + basement membrane
Capillary endothelial cells + basement membrane
0.2 microns thick
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32. Scanning Electron Micrograph of Bronchiole and Alveoli
Figure 17.5e
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33. Resin Cast of Blood Vessels to the Lungs
Figure 17.6a
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34. Scanning Electron Micrograph of Capillaries Around Alveoli
Figure 17.6b
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35. Structures of the Thoracic Cavity
Chest wall – air tight, protects lungs
Rib cage
Sternum
Thoracic vertebrae
Muscles - internal/external intercostals, diaphragm
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36. Structures of the Thoracic Cavity
Pleura – membrane lining of lungs and chest wall
Pleural sac around each lung
Intrapleural space filled with intrapleural fluid
Volume = 15 mL
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37. Chest Wall and Pleural Sac
Figure 17.7
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38. Role of Pressure in Pulmonary Ventilation
Air moves in and out of lungs by bulk flow
Pressure gradient drives flow
Air moves from high to low pressure
Inspiration: pressure in lungs less than atmosphere
Expiration: pressure in lungs greater than atmosphere
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39. III. Forces for Pulmonary Ventilation
Pulmonary Pressures
Mechanics of Breathing
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40. Pulmonary Pressures Atmospheric pressure = Patm
Intra-alveolar pressure = Palv
Pressure of air in alveoli
Intrapleural pressure = Pip
Pressure inside pleural sac
Transpulmonary pressure = Palv – Pip
Distending pressure across the lung wall
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41. Atmospheric Pressure 760 mm Hg at sea level
Decreases as altitude increases
Increases under water
Other lung pressures given relative to atmospheric (set Patm = 0 mm Hg)
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42. Intra-alveolar Pressure
Pressure of air in alveoli
Given relative to atmospheric pressure
Varies with phase of respiration
During inspiration = negative (less than atmospheric)
During expiration = positive (more than atmospheric)
Difference between Palv and Patm drives ventilation
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43. Intrapleural Pressure
Pressure inside pleural sac
Always negative under normal conditions
Always less than Palv
Varies with phase of respiration
At rest, -4 mm Hg
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44. Intrapleural Pressure
Negative pressure due to elasticity in lungs and chest wall
Lungs recoil inward
Chest wall recoils outward
Opposing pulls on intrapleural space
Surface tension of intrapleural fluid hold wall and lungs together
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45. Transpulmonary Pressure
Transpulmonary pressure = Palv – Pip
Distending pressure across the lung wall
Increase in transpulmonary pressure:
Increase distending pressure across lungs
Lungs (alveoli) expand, increasing volume
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46. Pulmonary Pressures at Rest
FRC = Functional Residual Capacity = volume of air in lungs between breaths (defined as rest); Palv = Patm
Figure 17.8
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47. Pneumothorax
Figure 17.9
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48. Mechanics of Breathing
Movement of air in and out of lungs due to pressure gradients
Mechanics of breathing describes mechanisms for creating pressure gradients
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49. Forces for Air Flow Patm – Palv Flow = R
Force for flow = pressure gradient
Atmospheric pressure constant (during breathing cycle)
Therefore, changes in alveolar pressure creates/changes gradients
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50. Forces for Air Flow
Boyle’s Law: pressure is inversely related to volume
Thus – can change alveolar pressure by changing its volume
R = resistance to air flow
Resistance related to radius of airways and mucus
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51. Determinants of Intra-Alveolar Pressure
Factors determining intra-alveolar pressure
Quantity of air in alveoli
Volume of alveoli
Lungs expand – alveolar volume increases
Palv decreases
Pressure gradient drives air into lungs
Lungs recoil – alveolar volume decreases
Palv increases
Pressure gradient drives air out of lungs
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52. Changes in Intra-Alveolar Pressure During Respiration
Figure 17.10
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53. Muscles of Respiration
Inspiratory muscles increase volume of thoracic cavity
Diaphragm
External intercostals
Expiratory muscles decrease volume of thoracic cavity
Internal intercostals
Abdominal muscles
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54. Muscles of Respiration
Expiration is generally passive (no muscles required)
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55. Respiratory Muscles Figure 17.11a
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56. Inspiration and Expiration
Figure 17.11b
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57. Neural Control of Inspiration
Figure 17.12
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58. Volume and Pressure Changes: Inspiration and Expiration
Figure 17.13a, b
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59. Expiration Expiration normally a passive process
When inspiratory muscles stop contracting, recoil of lungs and chest wall to original positions decreases volume of thoracic cavity
Active expiration requires expiratory muscles
Contraction of expiratory muscles creates greater and faster decrease in volume of thoracic cavity
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60. IV. Factors Affecting Pulmonary Ventilation
Lung Compliance
Airway Resistance
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61. Lung Compliance Ease with which lungs can be stretched V
(Palv – Pip)
Larger lung compliance
Easier to inspire
Smaller change in transpulmonary pressure needed to bring in a given volume of air
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62. Factors Affecting Lung Compliance
Elasticity
More elastic  less compliant
Surface tension of lungs
Greater tension  less compliant
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63. Surface Tension in Lungs
Thin layer fluid lines alveoli
Surface tension due to attractions between water molecules
Surface tension = force for alveoli to collapse or resist expansion
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64. To Overcome Surface Tension
Surfactant secreted from type II cells
Surfactant = detergent that decreases surface tension
Surfactant increases lung compliance
Makes inspiration easier
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65. Factors Affecting Lung Volume
Figure 17.14
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66. Airway Resistance
As airways get smaller in diameter they increase in number, keeping overall resistance low
Pressure gradient needed for air flow thus low
~1 mm Hg
An increase in resistance makes it harder to breathe
Pressure gradient needed for air flow > 1 mm Hg
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67. Effects of Resistance on Required Pressure Gradient
Figure 17.15
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68. Factors Affecting Airway Resistance
Passive Forces
Changes in transpulmonary pressure during respiratory cycle
Inspiration: transpulmonary pressure increases causing airways to expand
Tractive forces
Inspiration: as tissue moves away from airways, they pull the airways open
Contractile Activity of Smooth Muscle
Mucus Secretion
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69. Role of Bronchiolar Smooth Muscle in Airway Resistance
Bronchoconstriction – smooth muscle contracts causing radius to decrease
Bronchodilation – smooth muscle relaxes causing radius to increase
Contractile state of bronchiolar smooth muscle under extrinsic and intrinsic controls
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70. Extrinsic Control of Bronchiole Radius
Autonomic nervous system
Sympathetic
Relaxation of smooth muscle
Bronchodilation
Parasympathetic
Contraction of smooth muscle
Bronchoconstriction
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71. Extrinsic Control of Bronchiole Radius
Hormonal Control
Epinephrine
Relaxation of smooth muscle
Bronchodilation
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72. Intrinsic Control of Bronchiole Radius
Histamine – bronchoconstriction
Released during asthma and allergies
Also increases mucus secretion
Carbon dioxide – bronchodilation
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73. Pathological States that Increase Airway Resistance
Asthma – caused by spastic contractions of bronchiolar smooth muscle
Chronic obstructive pulmonary diseases – COPD
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74. V. Clinical Significance of Respiratory Volumes and Air Flows
Lung Volumes and Capacities
Pulmonary Function Tests
Alveolar Ventilation
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75. Spirometry Method of measuring lung volumes
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76. Spirometry
Figure 17.16
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77. Lung Volumes and Capacities
Figure 17.17
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78. Obstructive Pulmonary Diseases
Associated with increased airway resistance
Residual volume increases (harder to expire)
Functional residual capacity increases
Total lung capacity increases
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79. Restrictive Pulmonary Diseases
More difficult for lungs to expand
Total lung capacity decreases
Vital capacity decreases
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80. Pulmonary Function Tests: Forced Vital Capacity (FVC)
Maximum volume inhale followed by exhale as fast as possible
Low FVC indicates restrictive pulmonary disease
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81. Pulmonary Function Tests: Forced Expiratory Volume (FEV)
Percentage of FVC that can be exhaled within certain time frame
FEV1 = percent of FVC that can be exhaled within 1 second
Normal FEV1 = 80%
(If FVC = 4000 ml, should expire 3200 ml in 1 sec)
FEV1 < 80% indicates obstructive pulmonary disease
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82. Minute Ventilation
Total volume of air entering and leaving respiratory system each minute
Minute ventilation = VT x RR
Normal respiration rate = 12 breaths/min
Normal VT = 500 mL
Normal minute ventilation =
500 mL x 12 breaths/min = 6000 mL/min
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83. Anatomical Dead Space
Air in conducting zone does not participate in gas exchange
Thus, conducting zone = anatomical dead space
Dead space approximately 150 mL
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84. Anatomical Dead Space Figure 17.18
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85. Alveolar Ventilation
Volume of air reaching gas exchange areas per minute
Alveolar Ventilation = (VT x RR) – (DSV x RR)
Normal Alveolar Ventilation =
(500 mL/br x 12 br/min) – (150 mL/br X 12 br/min) =
4200 mL/min
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86. Increasing Alveolar Ventilation
Can increase alveolar ventilation by increase VT or RR.
Increasing VT is more effective.
Table 17.1
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87. Summary of Minute Ventilation
Figure 17.19
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