1. Respiratory physiology:

2. Respiration Ventilation: Movement of air into and out of lungs
External respiration: Gas exchange between air in lungs and blood
Transport of oxygen and carbon dioxide in the blood
Internal respiration: Gas exchange between the blood and tissues

3. Respiratory System Functions
Gas exchange: Oxygen enters blood and carbon dioxide leaves
Regulation of blood pH: Altered by changing blood carbon dioxide levels
Voice production: Movement of air past vocal folds makes sound and speech
Olfaction: Smell occurs when airborne molecules drawn into nasal cavity
Protection: Against microorganisms by preventing entry and removing them

4. Respiratory System Divisions
Upper tract
Nose, pharynx and associated structures
Lower tract
Larynx, trachea, bronchi, lungs

5. Nasal Cavity and Pharynx

6. Nose and Pharynx Pharynx Nose
Common opening for digestive and respiratory systems
Three regions
Nasopharynx
Oropharynx
Laryngopharynx
Nose
External nose
Nasal cavity
Functions
Passageway for air
Cleans the air
Humidifies, warms air
Smell
Along with paranasal sinuses are resonating chambers for speech

7. Larynx Functions Maintain an open passageway for air movement
Epiglottis and vestibular folds prevent swallowed material from moving into larynx
Vocal folds are primary source of sound production

8. Vocal Folds

9. Trachea
Windpipe
Divides to form
Primary bronchi
Carina: Cough reflex

10. Tracheobronchial Tree
Conducting zone
Trachea to terminal bronchioles which is ciliated for removal of debris
Passageway for air movement
Cartilage holds tube system open and smooth muscle controls tube diameter
Respiratory zone
Respiratory bronchioles to alveoli
Site for gas exchange

11. Tracheobronchial Tree

12. Bronchioles and Alveoli

13. Alveolus and Respiratory Membrane

15. Fig. 4. Effects of methacholine on depth of airway
surface liquid. a: control tissue not exposed to methacholine.
b: 2-min methacholine exposure. Putative
sol and mucous gel are clearly visible. c: 30-min
exposure. Tissues were radiant etched for 20 s to 1
min. Scale bar 5 20 μm.
From Am. J. Physiol. 274 (Lung Cell. Mol. Physiol. 18): L388–L395, 1998.—

16. Lungs Two lungs: Principal organs of respiration Divisions
Right lung: Three lobes
Left lung: Two lobes
Divisions
Lobes, bronchopulmonary segments, lobules

17. Thoracic Walls Muscles of Respiration

18. Thoracic Volume

20. Pleura Pleural fluid produced by pleural membranes Acts as lubricant
Helps hold parietal and visceral pleural membranes together

21. Ventilation Movement of air into and out of lungs
Air moves from area of higher pressure to area of lower pressure
Pressure is inversely related to volume

22. Alveolar Pressure Changes

23. Changing Alveolar Volume
Lung recoil
Causes alveoli to collapse resulting from
Elastic recoil and surface tension
Surfactant: Reduces tendency of lungs to collapse
Pleural pressure
Negative pressure can cause alveoli to expand
Pneumothorax is an opening between pleural cavity and air that causes a loss of pleural pressure

24. Normal Breathing Cycle

25. Compliance Measure of the ease with which lungs and thorax expand
The greater the compliance, the easier it is for a change in pressure to cause expansion
A lower-than-normal compliance means the lungs and thorax are harder to expand
Conditions that decrease compliance
Pulmonary fibrosis
Pulmonary edema
Respiratory distress syndrome

26. Pulmonary Volumes Tidal volume Inspiratory reserve volume
Volume of air inspired or expired during a normal inspiration or expiration
Inspiratory reserve volume
Amount of air inspired forcefully after inspiration of normal tidal volume
Expiratory reserve volume
Amount of air forcefully expired after expiration of normal tidal volume
Residual volume
Volume of air remaining in respiratory passages and lungs after the most forceful expiration

27. Pulmonary Capacities Inspiratory capacity Functional residual capacity
Tidal volume plus inspiratory reserve volume
Functional residual capacity
Expiratory reserve volume plus the residual volume
Vital capacity
Sum of inspiratory reserve volume, tidal volume, and expiratory reserve volume
Total lung capacity
Sum of inspiratory and expiratory reserve volumes plus the tidal volume and residual volume

28. Spirometer and Lung Volumes/Capacities

29. Minute and Alveolar Ventilation
Minute ventilation: Total amount of air moved into and out of respiratory system per minute
Respiratory rate or frequency: Number of breaths taken per minute
Anatomic dead space: Part of respiratory system where gas exchange does not take place
Alveolar ventilation: How much air per minute enters the parts of the respiratory system in which gas exchange takes place

31. Physical Principles of Gas Exchange
Partial pressure
The pressure exerted by each type of gas in a mixture
Dalton’s law
Water vapor pressure
Diffusion of gases through liquids
Concentration of a gas in a liquid is determined by its partial pressure and its solubility coefficient
Henry’s law

36. Physical Principles of Gas Exchange
Diffusion of gases through the respiratory membrane
Depends on membrane’s thickness, the diffusion coefficient of gas, surface areas of membrane, partial pressure of gases in alveoli and blood
Relationship between ventilation and pulmonary capillary flow
Increased ventilation or increased pulmonary capillary blood flow increases gas exchange
Physiologic shunt is deoxygenated blood returning from lungs

37. Oxygen and Carbon Dioxide Diffusion Gradients
Moves from alveoli into blood. Blood is almost completely saturated with oxygen when it leaves the capillary
P02 in blood decreases because of mixing with deoxygenated blood
Oxygen moves from tissue capillaries into the tissues
Carbon dioxide
Moves from tissues into tissue capillaries
Moves from pulmonary capillaries into the alveoli

38. Changes in Partial Pressures

40. Hemoglobin and Oxygen Transport
Oxygen is transported by hemoglobin (98.5%) and is dissolved in plasma (1.5%)
Oxygen-hemoglobin dissociation curve shows that hemoglobin is almost completely saturated when P02 is 80 mm Hg or above. At lower partial pressures, the hemoglobin releases oxygen.
A shift of the curve to the left because of an increase in pH, a decrease in carbon dioxide, or a decrease in temperature results in an increase in the ability of hemoglobin to hold oxygen

41. Hemoglobin and Oxygen Transport
A shift of the curve to the right because of a decrease in pH, an increase in carbon dioxide, or an increase in temperature results in a decrease in the ability of hemoglobin to hold oxygen
The substance 2.3-bisphosphoglycerate increases the ability of hemoglobin to release oxygen
Fetal hemoglobin has a higher affinity for oxygen than does maternal

42. Oxygen-Hemoglobin Dissociation Curve at Rest

43. Bohr effect:

44. Temperature effects:

46. Shifting the Curve

47. Transport of Carbon Dioxide
Carbon dioxide is transported as bicarbonate ions (70%) in combination with blood proteins (23%) and in solution with plasma (7%)
Hemoglobin that has released oxygen binds more readily to carbon dioxide than hemoglobin that has oxygen bound to it (Haldane effect)
In tissue capillaries, carbon dioxide combines with water inside RBCs to form carbonic acid which dissociates to form bicarbonate ions and hydrogen ions

49. Transport of Carbon Dioxide
In lung capillaries, bicarbonate ions and hydrogen ions move into RBCs and chloride ions move out. Bicarbonate ions combine with hydrogen ions to form carbonic acid. The carbonic acid is converted to carbon dioxide and water. The carbon dioxide diffuses out of the RBCs.
Increased plasma carbon dioxide lowers blood pH. The respiratory system regulates blood pH by regulating plasma carbon dioxide levels

50. Haldane Effect
The amount of carbon dioxide transported is markedly affected by the PO2
Haldane effect – the lower the PO2 and hemoglobin saturation with oxygen, the more carbon dioxide can be carried in the blood

51. Haldane Effect
At the tissues, as more carbon dioxide enters the blood:
More oxygen dissociates from hemoglobin (Bohr effect)
More carbon dioxide combines with hemoglobin, and more bicarbonate ions are formed
This situation is reversed in pulmonary circulation

53. Haldane Effect
Figure 22.23

54. CO2 Transport and Cl- Movement

55. Transport and Exchange of Carbon Dioxide
Figure 22.22a

56. Transport and Exchange of Carbon Dioxide
Figure 22.22b

57. Ventilation-Perfusion Coupling
Figure 22.19

58. Ventilation-perfusion coupling:

59. Respiratory Areas in Brainstem
Medullary respiratory center
Dorsal groups stimulate the diaphragm
Ventral groups stimulate the intercostal and abdominal muscles
Pontine (pneumotaxic) respiratory group
Involved with switching between inspiration and expiration

60. Respiratory Structures in Brainstem

61. Rhythmic Ventilation
Neurons controlling inspiration and expiration are clustered into two groups which make up the Respiratory Rhythmicity Centre (RRC) in the medulla.
The dorsal resp. group (DRG and the ventral resp. group (VRG) have reciprocal inhibition.
i.e. when one group is active, the other is inhibited.

62. Starting inspiration
Neurons of the DRG are spontaneously active in bursts (usually about 2 second burst duration during quiet breathing). Action potentials stimulate inspiratory muscles to contract.
Center receives stimulation from stretch receptors and simulation from parts of brain concerned with voluntary respiratory movements and emotion. These inputs can modify the bursting activity.

63. Stopping inspiration
DRG neurons become quiet. Inspiratory muscles relax, passive expiration occurs.
Neurons responsible for stopping inspiration, receive input from pontine group and stretch receptors in lungs. Inhibitory neurons activated and relaxation of respiratory muscles results in expiration.
Neurons in the VRG can become active, which instigates forced expiration.

65. Modification of Ventilation
Chemical control
Carbon dioxide is major regulator
Increase or decrease in pH can stimulate chemo- sensitive area, causing a greater rate and depth of respiration
Oxygen levels in blood affect respiration when a 50% or greater decrease from normal levels exists
Cerebral and limbic system
Respiration can be voluntarily controlled and modified by emotions

66. Higher Control of Breathing
Two centres found in the Pons can modify the rate generated by the RRC. These are the Apneustic centre and the Pneumotaxic centre.
The apneustic centre receives input from stretch receptors in the lungs and stimulates the DRG constantly; however, the stimulation intensity can vary. This stimulation increases the strength of the DRG signal (i.e. forced inspiration).

67. The pneumotaxic centre inhibits the apneustic centre.
The pneumotaxic centre receives input from higher brain centres.
Thus, the higher brain centres can force a different rhythm on the RRC.

71. Modification of Ventilation
Chemical control
Carbon dioxide is major regulator
Increase or decrease in pH can stimulate chemo- sensitive area, causing a greater rate and depth of respiration
Oxygen levels in blood affect respiration when a 50% or greater decrease from normal levels exists
Cerebral and limbic system
Respiration can be voluntarily controlled and modified by emotions

72. Modifying Respiration

73. Regulation of Blood pH and Gases

74. Herring-Breuer Reflex
Limits the degree of inspiration and prevents overinflation of the lungs
Infants
Reflex plays a role in regulating basic rhythm of breathing and preventing overinflation of lungs
Adults
Reflex important only when tidal volume large as in exercise

75. Ventilation in Exercise
Ventilation increases abruptly
At onset of exercise
Movement of limbs has strong influence
Learned component
Ventilation increases gradually
After immediate increase, gradual increase occurs (4-6 minutes)
Anaerobic threshold is highest level of exercise without causing significant change in blood pH
If exceeded, lactic acid produced by skeletal muscles

76. Effects of Aging
Vital capacity and maximum minute ventilation decrease
Residual volume and dead space increase
Ability to remove mucus from respiratory passageways decreases
Gas exchange across respiratory membrane is reduced