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SMP - Cardiopulmonary Exam 2 > Lecture 21 - Structure and Function of the Lung > Flashcards

Lecture 21 - Structure and Function of the Lung Flashcards

1
Q

How do biochemists define respiration?

A

The metabolic process that utilizes O2 and produces CO2

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2
Q

How do physiologists define respiration?

A

The transport of O2 from air to the cells and CO2 from the cells to the air

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3
Q

How do single cellular organisms transport O2? What is this dependent on?

A

Simple diffusion with a gas moving from an area of high pressure to an area of low pressure, dependent on surface area

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4
Q

How do large organisms transport O2? 3 components.

A
  1. Blood as a medium to carry O2
  2. Heart to pump blood
  3. Lung to be a component with a large surface area to exchange gas
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5
Q

What is the primary function of the lung?

A

Gas exchange

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6
Q

What are the 3 secondary functions of the lung?

A
  1. Metabolizes some compounds
  2. Filters unwanted material from the circulation and the air
  3. Acts as a reservoir of blood
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7
Q

What are the 2 types of respiratory failure?

A
  1. Hypoxia = not taking in enough O2 in lungs to bring to tissues
  2. Hypercapnia = not taking out enough CO2
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8
Q

What are the 2 ways in which the lung filters unwanted materials?

A
  1. From air like dust or fumes

2. From circulation like blood clots

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9
Q

Where do most blood clots occur? Why?

A

In venous system because higher chance of blood stagnation

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10
Q

What are the 4 stages of respiration in terms of O2? Describe each. Which ones are driven by diffusion?

A
  1. Stage I = ventilation = O2 from ambient air to alveolus
  2. ***Stage II = pulmonary gas exchange = diffusion of O2 at alveolar-capillary membrane
  3. Stage III = gas transport = O2 transported from capillaries to the peripheral capillaries by the circulation pump
  4. ***Stage IV = peripheral gas exchange = diffusion of O2 from the peripheral capillaries to the cells
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11
Q

What are the 4 stages of respiration in terms of CO2?

A

Same as for O2 but opposite order

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12
Q

What are the 2 types of systems of airways? Volume of each?

A
  1. Conductive system: 150 mL

2. Gas exchange system: 2.5-3 L

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13
Q

What are 2 other names for conduction airway?

A
  1. Anatomic dead space

2. Transitional zone

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14
Q

What are the 6 components of the conductive system of the airways? How many generations of bifurcations does this comprise?

A
  1. Nasopharynx
  2. Trachea
  3. Main bronchi
  4. Lobar bronchi
  5. Segmental bronchi
  6. Terminal bronchioles

First 16 generations

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15
Q

What are the 3 components of the gas exchange system of the airways? Do all of them have alveoli? How many generations of bifurcations does this comprise?

A
  1. Respiratory bronchioles
  2. Alveolar ducts
  3. Alveoli

YES, they all have alveoli

Last 7 generations

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16
Q

Difference between bronchi and bronchioles?

A

Presence of cartilaginous rings for support that is present in bronchi but absent in bronchioles

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17
Q

How do sherpa differ anatomically from other humans?

A

They have more lung aka more generations of airways

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18
Q

How many terminal bronchioles are there?

A

70,000

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19
Q

Generation number of bronchi?

A

1-3

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20
Q

Generation number of bronchioles?

A

4-15

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21
Q

Generation number of terminal bronchioles?

A

16

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22
Q

Generation number of respiratory bronchioles?

A

17-19

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23
Q

Generation number of alveolar ducts?

A

20-22

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24
Q

Generation number of alveolar sacs?

A

23

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25
Q

Generation number of alveolar sacs?

A

23

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26
Q

What are the acini?

A

The airway generations distal to the bronchioles:

  1. Respiratory bronchioles
  2. Alveolar ducts
  3. Alveoli
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27
Q

How does the cross-sectional area of each subsequent generation of branches differ from the previous generation?

A

Cross-sectional area is greater once we pass the 4th generation - it doubles with each generation

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28
Q

Which cross-sectional area is greater: that of the respiratory zone or the conducting zone?

A

The respiratory zone cross-sectional area

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29
Q

Which airway generation is the narrowest aka has the smallest cross-sectional area?

A

4th

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30
Q

In which portion of the airways is the composition of O2 and CO2 homogenous?

A

The respiratory zone

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31
Q

What happens during inspiration?

A

Diaphragm and intercostal muscles contract to expand the thoracic cavity => negative pressure in the chest => causes the air to travel through the conducting zone via bulk flow => once the air reaches the respiratory zone, there is no more bulk flow due to the huge increase in cross sectional area => forward velocity of gas becomes slow => diffusion becomes the dominant mechanism of ventilation

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32
Q

What is compliance?

A

Amount of pressure required to bring a certain volume change

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33
Q

What does it mean for a structure to be very compliant?

A

Little pressure is required to change the volume of the structure

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34
Q

What does it mean for a structure to be noncompliant?

A

A lot of pressure is required to change the volume of the structure

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35
Q

What is elasticity?

A

Inverse of compliance = amount of volume required to bring a certain pressure change

36
Q

What are the 2 equations to calculate compliance?

A

Compliance = ΔV/ΔP = 1/elasticity

37
Q

Volume of normal breath?

A

500 mL

38
Q

How does the lung return to its pre-inspiratory volume?

A

Passively as it is elastic

39
Q

What change in pressure is caused by a normal breath?

A

Distending pressure of less than 3 cm of water

40
Q

Surface area of the blood-gas interface?

A

50-100 m^2

41
Q

How many alveoli do humans have?

A

300 million

42
Q

What are the alveoli covered by on the air side?

A

Surfactant

43
Q

Describe the blood gas interface.

A

VERY thin

44
Q

What are the 2 pathologies associated with the alveolar interstitium?

A
  1. Interstitial fibrosis

2. Sarcoidosis

45
Q

What are the 3 layers of the alveolar walls? List from inner to outer.

A
  1. Epithelium
  2. Interstitium
  3. Endothelium
46
Q

What is interstitial fibrosis?

A

Invasion of the interstitial space by fiber cells

47
Q

What is sarcoidosis?

A

Autoimmune disease in which the immune system believes the lung is abnormal and causes inflammation of the pulmonary interstitium

48
Q

Passage of O2 from air to RBC pathway?

A

Air => alveolar epithelium => interstitium with fused basal laminae => capillary endothelium => pulmonary capillary => RBC

49
Q

What are the 2 types of pulmonary alveolar cells? Describe each.

A
  1. Type I pneumocytes = large flattened cells used for gas exchange
  2. Type II pneumocytes = large cuboidal cells that are synthetic secretory cells
50
Q

Are there more type I or II pneumocytes? Which ones account for most of the lung surface?

A

Twice as many type II pneumocytes BUT type I account for 90% of the lung surface

51
Q

Through what mechanism does gas exchange occur?

A

Simple diffusion from high to low partial pressure

52
Q

What is the rate at which diffusion occurs for pulmonary gas exchange defined by? Equation?

A

Defined by Fick’s law of diffusion:

°Vgas=(A/T) x D x (P1-P2)

°Vgas = volume of gas per unit time
A = surface area
T = thickness of the tissue sheet the gas is diffusing across
D = diffusion constant
P1 and P2 = partial pressures of the gas on either sides of the tissue sheet

53
Q

Define the diffusion constant.

A

Solubility over the square root of the molecular weight of the molecule

54
Q

Which diffuses at a faster rate: O2 or CO2? Why?

A

They have relatively similar molecular weights, but the solubility of carbon dioxide is 20 times that of oxygen. So, carbon dioxide can diffuse at a much faster rate than oxygen

55
Q

What is the atmospheric pressure at sea level? How much of it is due to O2?

A

760 mmHg

160 mmHg due to O2

56
Q

What % of atmospheric air is O2? Notation? Does this vary with altitude?

A

Fraction of Inspired Oxygen = FiO2 = 21%

NOPE

57
Q

What is Dalton’s Law of partial pressures?

A

In a mixture of gases, each gas exerts a partial pressure proportional to its fraction

58
Q

Pressure exerted by water vapor in airways?

A

47 mmHg

59
Q

Pressure exerted by O2 gas in trachea?

A

150 mmHg

60
Q

How to calculate PO2 in the respiratory zone of the airway?

A

Alveolar Oxygen Equation:

Palv O2 = (760-47) x FiO2 – PaCO2/0.8 = 713 x FiO2 – PaCO2/0.8

PalvO2 = alveolar oxygen pressure 
FiO2 = fraction of O2 in the conducting zone
PaCO2 = arterial carbon dioxide pressure
0.8 = respiratory quotient accounting for difference between the amount of O2 entering the body vs the amount of CO2 leaving (5/4 ratio)
61
Q

Is the PO2 higher in the conducting zone or the respiratory zone of the airway? Why?

A

Conducting zone because O2 is leaving the airways to enter the blood and CO2 is entering the airways

62
Q

Are Palv CO2 and O2 directly measurable?

A

NOPE

63
Q

How to determine Palv CO2?

A

Measure arterial PCO2 because CO2 has a high diffusion coefficient and therefore will diffuse and equilibrate quickly with the levels present in the blood

64
Q

What is the normal PCO2 in adults?

A

40 mmHg

65
Q

Palv O2 at room air in a normal adult at sea level?

A

Palv O2 = (760-47) x FiO2 – PaCO2/0.8 = 713 x FiO2 – PaCO2/0.8 = 713 x 0.21 - 40/0.8 = 100 mmHg

66
Q

How to differentiate between arterial and alveolar partial pressures?

A

Alveolar: A
Arterial: a

67
Q

What is 713 x 0.21 = ?

A

151 (like Baccardi)

68
Q

What is 40/0.8 = ?

A

50

69
Q

Partial pressures in room?

A
  1. O2 = 160

2. N2 = 600

70
Q

Partial pressures in trachea?

A
  1. O2 = 150
  2. H2O = 47
  3. N2 = 563
71
Q

Partial pressures in alveoli?

A
  1. CO2 = 40
  2. O2 = 100
  3. H2O = 47
  4. N2 = 573
72
Q

Partial pressures in arterial blood? Total?

A
  1. CO2 = 40
  2. O2 = 95
  3. N2 = 578

Total = 713 mmHg

73
Q

At rest, how much time will an RBC spend in a pulmonary capillary? Does this allow for complete equilibration of O2 and CO2?

A

3/4 of a second

YUP

74
Q

Does the aorta have 100% CO?

A

NOPE, because it loses some blood to the coronary arteries

75
Q

What is the nutritive blood supply of the lung?

A

Bronchial arteries to the conducting zone and pleural surface

76
Q

Is the bronchial arterial system necessary for lung function? Example?

A

NOPE, for example in a lung transplant because it’s a mere fraction of the pulmonary arterial flow

77
Q

Diameter of pulmonary capillary? What does this correspond to?

A

10 micrometers = 1 RBC

78
Q

Resistance in pulmonary artery?

A

Low

79
Q

In how much time is there complete equilibration of O2 and CO2 between RBC and alveolus?

A

1/4 of a second

80
Q

Pathway of bronchial blood supply to lungs?

A

Aorta => intercostal arteries => bronchial arteries

81
Q

When we bleed into our respiratory system due to pathologies, is the blood coming from the pulmonary system or the bronchial system? Why? Example? Treatment? Exception?

A

Bronchial because it is a high pressure system

Example: tuberculosis

Treatment: Catheter in femoral artery to find the bronchial artery that is bleeding and embolize it

Exception: lung catheter stuck in pulmonary arteriole, which pops when the balloon is inflated

82
Q

What does hemoptysis mean?

A

Coughing up blood

83
Q

How to calculate PO2 in trachea when given the atmospheric pressure?

A

First subtract the 47 mmHg of water vapor pressure and then multiply by 0.21

84
Q

How many alveolar sacs in humans?

A

8 million

85
Q

How many respiratory bronchioles?

A

500,000

86
Q

What is another name for gas exchange airway?

A

Respiratory zone

SMP - Cardiopulmonary Exam 2 (15 decks)

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