Lecture 21 - Structure and Function of the Lung Flashcards
(86 cards)
1
Q
How do biochemists define respiration?
A
The metabolic process that utilizes O2 and produces CO2
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
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
4
Q
How do large organisms transport O2? 3 components.
A
- Blood as a medium to carry O2
- Heart to pump blood
- Lung to be a component with a large surface area to exchange gas
5
Q
What is the primary function of the lung?
A
Gas exchange
6
Q
What are the 3 secondary functions of the lung?
A
- Metabolizes some compounds
- Filters unwanted material from the circulation and the air
- Acts as a reservoir of blood
7
Q
What are the 2 types of respiratory failure?
A
- Hypoxia = not taking in enough O2 in lungs to bring to tissues
- Hypercapnia = not taking out enough CO2
8
Q
What are the 2 ways in which the lung filters unwanted materials?
A
- From air like dust or fumes
2. From circulation like blood clots
9
Q
Where do most blood clots occur? Why?
A
In venous system because higher chance of blood stagnation
10
Q
What are the 4 stages of respiration in terms of O2? Describe each. Which ones are driven by diffusion?
A
- Stage I = ventilation = O2 from ambient air to alveolus
- ***Stage II = pulmonary gas exchange = diffusion of O2 at alveolar-capillary membrane
- Stage III = gas transport = O2 transported from capillaries to the peripheral capillaries by the circulation pump
- ***Stage IV = peripheral gas exchange = diffusion of O2 from the peripheral capillaries to the cells
11
Q
What are the 4 stages of respiration in terms of CO2?
A
Same as for O2 but opposite order
12
Q
What are the 2 types of systems of airways? Volume of each?
A
- Conductive system: 150 mL
2. Gas exchange system: 2.5-3 L
13
Q
What are 2 other names for conduction airway?
A
- Anatomic dead space
2. Transitional zone
14
Q
What are the 6 components of the conductive system of the airways? How many generations of bifurcations does this comprise?
A
- Nasopharynx
- Trachea
- Main bronchi
- Lobar bronchi
- Segmental bronchi
- Terminal bronchioles
First 16 generations
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
- Respiratory bronchioles
- Alveolar ducts
- Alveoli
YES, they all have alveoli
Last 7 generations
16
Q
Difference between bronchi and bronchioles?
A
Presence of cartilaginous rings for support that is present in bronchi but absent in bronchioles
17
Q
How do sherpa differ anatomically from other humans?
A
They have more lung aka more generations of airways
18
Q
How many terminal bronchioles are there?
A
70,000
19
Q
Generation number of bronchi?
A
1-3
20
Q
Generation number of bronchioles?
A
4-15
21
Q
Generation number of terminal bronchioles?
A
16
22
Q
Generation number of respiratory bronchioles?
A
17-19
23
Q
Generation number of alveolar ducts?
A
20-22
24
Q
Generation number of alveolar sacs?
A
23
25
Generation number of alveolar sacs?
23
26
What are the acini?
The airway generations distal to the bronchioles:
1. Respiratory bronchioles
2. Alveolar ducts
3. Alveoli
27
How does the cross-sectional area of each subsequent generation of branches differ from the previous generation?
Cross-sectional area is greater once we pass the 4th generation - it doubles with each generation
28
Which cross-sectional area is greater: that of the respiratory zone or the conducting zone?
The respiratory zone cross-sectional area
29
Which airway generation is the narrowest aka has the smallest cross-sectional area?
4th
30
In which portion of the airways is the composition of O2 and CO2 homogenous?
The respiratory zone
31
What happens during inspiration?
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
32
What is compliance?
Amount of pressure required to bring a certain volume change
33
What does it mean for a structure to be very compliant?
Little pressure is required to change the volume of the structure
34
What does it mean for a structure to be noncompliant?
A lot of pressure is required to change the volume of the structure
35
What is elasticity?
Inverse of compliance = amount of volume required to bring a certain pressure change
36
What are the 2 equations to calculate compliance?
Compliance = ΔV/ΔP = 1/elasticity
37
Volume of normal breath?
500 mL
38
How does the lung return to its pre-inspiratory volume?
Passively as it is elastic
39
What change in pressure is caused by a normal breath?
Distending pressure of less than 3 cm of water
40
Surface area of the blood-gas interface?
50-100 m^2
41
How many alveoli do humans have?
300 million
42
What are the alveoli covered by on the air side?
Surfactant
43
Describe the blood gas interface.
VERY thin
44
What are the 2 pathologies associated with the alveolar interstitium?
1. Interstitial fibrosis
| 2. Sarcoidosis
45
What are the 3 layers of the alveolar walls? List from inner to outer.
1. Epithelium
2. Interstitium
3. Endothelium
46
What is interstitial fibrosis?
Invasion of the interstitial space by fiber cells
47
What is sarcoidosis?
Autoimmune disease in which the immune system believes the lung is abnormal and causes inflammation of the pulmonary interstitium
48
Passage of O2 from air to RBC pathway?
Air => alveolar epithelium => interstitium with fused basal laminae => capillary endothelium => pulmonary capillary => RBC
49
What are the 2 types of pulmonary alveolar cells? Describe each.
1. Type I pneumocytes = large flattened cells used for gas exchange
2. Type II pneumocytes = large cuboidal cells that are synthetic secretory cells
50
Are there more type I or II pneumocytes? Which ones account for most of the lung surface?
Twice as many type II pneumocytes BUT type I account for 90% of the lung surface
51
Through what mechanism does gas exchange occur?
Simple diffusion from high to low partial pressure
52
What is the rate at which diffusion occurs for pulmonary gas exchange defined by? Equation?
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
Define the diffusion constant.
Solubility over the square root of the molecular weight of the molecule
54
Which diffuses at a faster rate: O2 or CO2? Why?
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
What is the atmospheric pressure at sea level? How much of it is due to O2?
760 mmHg
160 mmHg due to O2
56
What % of atmospheric air is O2? Notation? Does this vary with altitude?
Fraction of Inspired Oxygen = FiO2 = 21%
NOPE
57
What is Dalton's Law of partial pressures?
In a mixture of gases, each gas exerts a partial pressure proportional to its fraction
58
Pressure exerted by water vapor in airways?
47 mmHg
59
Pressure exerted by O2 gas in trachea?
150 mmHg
60
How to calculate PO2 in the respiratory zone of the airway?
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
Is the PO2 higher in the conducting zone or the respiratory zone of the airway? Why?
Conducting zone because O2 is leaving the airways to enter the blood and CO2 is entering the airways
62
Are Palv CO2 and O2 directly measurable?
NOPE
63
How to determine Palv CO2?
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
What is the normal PCO2 in adults?
40 mmHg
65
Palv O2 at room air in a normal adult at sea level?
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
How to differentiate between arterial and alveolar partial pressures?
Alveolar: A
Arterial: a
67
What is 713 x 0.21 = ?
151 (like Baccardi)
68
What is 40/0.8 = ?
50
69
Partial pressures in room?
1. O2 = 160
| 2. N2 = 600
70
Partial pressures in trachea?
1. O2 = 150
2. H2O = 47
3. N2 = 563
71
Partial pressures in alveoli?
1. CO2 = 40
2. O2 = 100
3. H2O = 47
4. N2 = 573
72
Partial pressures in arterial blood? Total?
1. CO2 = 40
2. O2 = 95
3. N2 = 578
Total = 713 mmHg
73
At rest, how much time will an RBC spend in a pulmonary capillary? Does this allow for complete equilibration of O2 and CO2?
3/4 of a second
YUP
74
Does the aorta have 100% CO?
NOPE, because it loses some blood to the coronary arteries
75
What is the nutritive blood supply of the lung?
Bronchial arteries to the conducting zone and pleural surface
76
Is the bronchial arterial system necessary for lung function? Example?
NOPE, for example in a lung transplant because it's a mere fraction of the pulmonary arterial flow
77
Diameter of pulmonary capillary? What does this correspond to?
10 micrometers = 1 RBC
78
Resistance in pulmonary artery?
Low
79
In how much time is there complete equilibration of O2 and CO2 between RBC and alveolus?
1/4 of a second
80
Pathway of bronchial blood supply to lungs?
Aorta => intercostal arteries => bronchial arteries
81
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?
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
What does hemoptysis mean?
Coughing up blood
83
How to calculate PO2 in trachea when given the atmospheric pressure?
First subtract the 47 mmHg of water vapor pressure and then multiply by 0.21
84
How many alveolar sacs in humans?
8 million
85
How many respiratory bronchioles?
500,000
86
What is another name for gas exchange airway?
Respiratory zone
