1. The Respiratory System
Chapter 23
(6th edition chapter 22)

2. Functions of the Respiratory System
Supply oxygen to the circulatory system for delivery to the tissues
Remove CO2 (and some other wastes) from blood.

3. There are 4 processes that we call “respiration”.
Pulmonary ventilation - Movement of air into and out of the lungs
(also referred to as “breathing”).
2. External respiration - Gas exchange in the lungs between the blood
of the capillaries and the spaces in the air sacs (alveoli)
Transport - The movement of gases by the circulatory system
Strictly speaking, a function of the blood.
Internal respiration - Gas exchange between the blood and the
tissues of the body

4. Overview of respiratory system anatomy

5. External Structures of the nose

6. Internal anatomy of the upper respiratory tract

7. The larynx and associated structures

8. The Glottis
Figure 23–5

9. Respiratory epithelium

10. Anatomy of the Trachea
Figure 23–6

11. Cross section of the trachea and esophagus

12. Gross Anatomy of the Lungs
Figure 23–7

13. Bronchi and Lobules
Figure 23–9

14. Secondary Bronchi
Branch to form tertiary bronchi, also called the segmental bronchi
Each segmental bronchus:
supplies air to a single bronchopulmonary segment

15. Bronchopulmonary Segments
The right lung has 10
The left lung has 8 or 9

16. Bronchial Structure
The walls of primary, secondary, and tertiary bronchi:
contain progressively less cartilage and more smooth muscle
increasing muscular effects on airway constriction and resistance

17. The Bronchioles
Figure 23–10

18. The Bronchioles
Each tertiary bronchus branches into multiple bronchioles
Bronchioles branch into terminal bronchioles:
1 tertiary bronchus forms about 6500 terminal bronchioles

19. Bronchiole Structure Bronchioles: have no cartilage
are dominated by smooth muscle

20. Asthma Excessive stimulation and bronchoconstriction
Stimulation severely restricts airflow

21. Alveolar Organization
Figure 23–11

22. Alveolar Epithelium Consists of simple squamous epithelium
Consists of thin, delicate Type I cells
Patrolled by alveolar macrophages, also called dust cells
Contains septal cells (Type II cells) that produce surfactant

23. Surfactant Is an oily secretion Contains phospholipids and proteins
Coats alveolar surfaces and reduces surface tension

24. Respiratory Distress Difficult respiration: due to alveolar collapse
caused when septal cells do not produce enough surfactant

25. Respiratory Membrane
The thin membrane of alveoli where gas exchange takes place

26. 3 Parts of the Respiratory Membrane
Squamous epithelial lining of alveolus
Endothelial cells lining an adjacent capillary
Fused basal laminae between alveolar and endothelial cells

27. Alveoli and the respiratory membrane

28. Structure of an alveolar sac

29. Pleural Cavities and Pleural Membranes
are separated by the mediastinum
Each pleural cavity:
holds a lung
is lined with a serous membrane (the pleura)

30. Pleural Cavities and Pleural Membranes
Figure 23–8

31. The Pleura Consists of 2 layers: Pleural fluid: parietal pleura
visceral pleura
Pleural fluid:
lubricates space between 2 layers

32. Respiratory Physiology
Boyle’s law: P = 1/V or
P1V1 = P2V2

33. Pressure relationships The negative intrapleural pressure keeps the lungs inflated

34. Mechanisms of Pulmonary Ventilation
Figure 23–14

35. Mechanics of Breathing: Inspiration

36. Mechanics of Breathing: Expiration

37. Compliance of the Lung An indicator of expandability
Low compliance requires greater force
High compliance requires less force

38. Factors That Affect Compliance
Connective-tissue structure of the lungs
Level of surfactant production
Mobility of the thoracic cage

39. Gas Pressure Can be measured inside or outside the lungs
Normal atmospheric pressure:
1 atm or Patm at sea level: 760 mm Hg

40. Pressure and Volume Changes with Inhalation and Exhalation

41. Intrapulmonary Pressure
Also called intra-alveolar pressure
Is relative to Patm
In relaxed breathing, the difference between Patm and intrapulmonary pressure is small:
about —1 mm Hg on inhalation or +1 mm Hg on expiration

42. Maximum Intrapulmonary Pressure
Maximum straining, a dangerous activity, can increase range:
from —30 mm Hg to +100 mm Hg

43. Intrapleural Pressure
Pressure in space between parietal and visceral pleura
Averages —4 mm Hg
Maximum of —18 mm Hg
Remains below Patm throughout respiratory cycle

44. Injury to the Chest Wall
Pneumothorax:
allows air into pleural cavity
Atelectasis:
also called a collapsed lung
result of pneumothorax

45. Respiratory Physiology
Resistance:
F = P/R
R = resistance
P = change in pressure (the pressure gradient)

46. Respiratory Volumes and Capacities
Figure 23–17

47. Gas Exchange Depends on: partial pressures of the gases
diffusion of molecules between gas and liquid

48. The Gas Laws Diffusion occurs in response to concentration gradients
Rate of diffusion depends on physical principles, or gas laws
e.g., Boyle’s law

49. Composition of Air Nitrogen (N2) about 78.6% Oxygen (O2) about 20.9%
Water vapor (H2O) about 0.5%
Carbon dioxide (CO2) about 0.04%

50. Gas Pressure Atmospheric pressure (760 mm Hg):
produced by air molecules bumping into each other
Each gas contributes to the total pressure:
in proportion to its number of molecules (Dalton’s law)

51. Partial Pressure
The pressure contributed by each gas in the atmosphere
All partial pressures together add up to 760 mm Hg

52. Respiratory Physiology: Dalton’s Law of Partial Pressures
The total pressure of a mixture of gases is the sum of the partial
pressures exerted independently by each gas in the mixture.
Location
Atmosphere at sea level
Alveoli of lungs
Gas
Approximate %
Partial pressure in mmHg N2
78.6
597
74.9
569 O2
20.9
159
13.7
104
CO2
0.04
0.3
5.2 40
H2O
0.46
3.7
6.2 47
Total
100.0
760

53. Partial pressure relationships: Movement of gases between the lungs and the tissues

54. Henry’s Law When gas under pressure comes in contact with liquid:
gas dissolves in liquid until equilibrium is reached
At a given temperature:
amount of a gas in solution is proportional to partial pressure of that gas

55. Henry’s Law
Figure 23–18

56. Diffusion and the Respiratory Membrane
Direction and rate of diffusion of gases across the respiratory membrane determine different partial pressures and solubilities

57. Efficiency of Gas Exchange
Due to:
– substantial differences in partial pressure across the respiratory membrane
– distances involved in gas exchange are small

58. Efficiency of Gas Exchange (2 of 2)
– O2 and CO2 are lipid soluble
– total surface area is large
– blood flow and air flow are coordinated

59. Most soluble Least soluble
Solubility: Differential solubility of gases contributes to the balance of gas exchange
Most soluble Least soluble
CO2 >>>>>>>>>>>>>>>>> O2 >>>>>>>>>>>>>>>>>>> N2
CO2 is 20 times more soluble than O2
N2 is about half as soluble as O2

60. Ventilation-Perfusion Coupling Breathing and blood flow are matched to the partial pressure of alveolar gases

61. The Oxyhemoglobin Saturation Curve
Is standardized for normal blood (pH 7.4, 37°C)
When pH drops or temperature rises:
more oxygen is released
curve shift to right
When pH rises or temperature drops:
less oxygen is released
curve shifts to left

62. Respiratory Gas Transport
Oxygen - about 98.5% is bound to hemoglobin (Hb) and 1.5% in solution.
Respiratory Gas Transport

63. pH, Temperature, and Hemoglobin Saturation

64. Factors influencing Hb saturation: Temperature

65. Factors influencing Hb saturation: Pco2 and pH

66. The Bohr Effect (1 of 2)
Is the effect of pH on hemoglobin saturation curve
Caused by CO2:
CO2 diffuses into RBC
an enzyme, called carbonic anhydrase, catalyzes reaction with H2O
produces carbonic acid (H2CO3)

67. The Bohr Effect Carbonic acid (H2CO3):
dissociates into hydrogen ion (H+) and bicarbonate ion (HCO3—)
Hydrogen ions diffuse out of RBC, lowering pH

68. 2,3-biphosphoglycerate (BPG)
RBCs generate ATP by glycolysis:
forming lactic acid and BPG
BPG directly affects O2 binding and release:
more BPG, more oxygen released

69. BPG Levels BPG levels rise: If BPG levels are too low:
when pH increases
when stimulated by certain hormones
If BPG levels are too low:
hemoglobin will not release oxygen

70. Fetal and Adult Hemoglobin
Figure 23–22

71. Fetal and Adult Hemoglobin
The structure of fetal hemoglobin:
differs from that of adult Hb
At the same PO2:
fetal Hb binds more O2 than adult Hb
which allows fetus to take O2 from maternal blood

72. CO2 Transport 7 % dissolved in the plasma
~ 23% bound to the amine groups of the Hb molecule as
carbaminohemoglobin
~ 70% as bicarbonate ion in the plasma

73. CO2 Transport & Exchange: at the tissues

74. CO2 Transport & Exchange: in the lungs

75. The Haldane Effect

76. Control of Respiration
Gas diffusion at peripheral and alveolar capillaries maintain balance by:
changes in blood flow and oxygen delivery
changes in depth and rate of respiration

77. Quiet Breathing Brief activity in the DRG:
stimulates inspiratory muscles
DRG neurons become inactive:
allowing passive exhalation

78. Quiet Breathing
Figure 23–25a

79. Forced Breathing
Figure 23–25b

80. The Apneustic and Pneumotaxic Centers of the Pons
Paired nuclei that adjust output of respiratory rhythmicity centers:
regulating respiratory rate and depth of respiration

81. Respiratory Centers and Reflex Controls
Figure 23–26

82. 5 Sensory Modifiers of Respiratory Center Activities
Chemoreceptors are sensitive to:
PCO2, PO2, or pH
of blood or cerebrospinal fluid
Baroreceptors in aortic or carotic sinuses:
sensitive to changes in blood pressure

83. 5 Sensory Modifiers of Respiratory Center Activities
Stretch receptors:
respond to changes in lung volume
Irritating physical or chemical stimuli:
in nasal cavity, larynx, or bronchial tree

84. 5 Sensory Modifiers of Respiratory Center Activities
Other sensations including:
pain
changes in body temperature
abnormal visceral sensations

85. Chemoreceptor Responses to PCO2

86. Hypercapnia An increase in arterial PCO2
Stimulates chemoreceptors in the medulla oblongata:
to restore homeostasis

87. Hypoventilation A common cause of hypercapnia
Abnormally low respiration rate:
allows CO2 build-up in blood

88. Hyperventilation Excessive ventilation
Results in abnormally low PCO2 (hypocapnia)
Stimulates chemoreceptors to decrease respiratory rate

89. Baroreceptor Reflexes
Carotid and aortic baroreceptor stimulation:
affects blood pressure and respiratory centers
When blood pressure falls:
respiration increases
When blood pressure increases:
respiration decreases

90. The Hering–Breuer Reflexes
2 baroreceptor reflexes involved in forced breathing:
inflation reflex:
prevents overexpansion of lungs
deflation reflex:
inhibits expiratory centers
stimulates inspiratory centers during lung deflation

91. Protective Reflexes
Triggered by receptors in epithelium of respiratory tract when lungs are exposed to:
toxic vapors
chemicals irritants
mechanical stimulation
Cause sneezing, coughing, and laryngeal spasm

92. Pathology and clinical considerations
Common homeostatic imbalances:
COPD (chronic obstructive pulmonary disease)
Asthma
Tuberculosis
Lung cancer

93. Respiratory Performance and Age
Figure 23–28

94. COPD: Emphysema
Results: Loss of lung elasticity, hypoxia, lung fibrosis, cyanosis.
Common causes: Industrial exposure, cigarette smoking.

95. Tuberculosis At the beginning of the 20th century a third of
all deaths in people
were from TB.
Antibiotic-resistant strains
of Mycobaterium tuberculosis
are a growing problem at the
beginning of the 21st century.

96. Lung Cancer

97. 90% of lung cancer patients had one thing in common…

98. …they smoked tobacco

99. Fin