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30 Cards in this Set
- Front
- Back
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1. What are several characteristics of bronchial circulation?
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1. Supplies major elements of respiratory tract
2. Represents only 1% of CO 3. Warms and humidifies air 4. Significant during oral breathing and breathing through a stoma |
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2. What is the bronchial circulation a nutrient supplier to?
(three things) |
1. Airways to terminal bronchioles
2. Outer tunics to pulmonary arteries and veins 3. Alveolar cells |
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3. What are two characteristics of pulmonary circulation?
How are pulmonary vessels? How is the compliance and resistance of pulmonary vessels? How is the pressure within pulmonary vessels? |
1. Receives nearly 100% of CO
2. Delivers blood to one side of alveolar membrane Short, thin walled, wide vessels that are branched High vascular compliance and low resistance to flow **20% to 25% of systemic circulation Low absolute pressures and small pressure gradient w/in vessels |
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4. How are systemic and pulmonary flows?
How do pressures in pulmonary vasculature compare to systemic arterial system pressure? How do pulmonary and systemic resistances compare? |
Systemic and pulmonary flows are equal
Pressures in pulmonary vasculature are only 20% to 25% of systemic arterial systemic pressures Pulmonary resistance is significantly less than systemic resistance |
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5. What is the primary function of pulmonary vasculature?
What is a secondary functions? What are some functions of endothelial cells of the pulmonary vasculature? (two things) |
Primary function is gas exchange
Filter blood by trapping 1. Contain enzymes to modify blood chemicals 2. Release substances that modify vascular tone (i.e nitric oxide) |
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6. What is the single most important factor which alters PVR (pulmonary vascular resistance)?
What are some other active determinants of PVR? |
Alveolar O2 tension (PAO2)
Vasoactive agents and ANS |
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7. What does lowered P2O2 result in?
What is the mechanism for this primarily dependent upon? How does hypoxia affect NO? |
Hypoxic vasoconstriction
Lack of nitric oxide (NO) **determines if NO synthase is active Hypoxia results in less formation of NO **hypoxia inhibits endothelial intracellular formaiton of NO synthase |
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8. What does lack of NO result in?
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Depolarization
1. Depolarization opens voltage sensitive Ca channels 2. Inward Ca flux contracts vascular smooth muscle constricting pulmonary vasculature **blood is shunted to another functional alveoli |
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9. How does NO result in less resistance?
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NO diffuses to smooth muscle cells and opens K channels on smooth muscle
Smooth muscle cells surrounding pulmonary vessels relax and diameter widens Resistance decreases |
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10. Are vasoactive agents effective in regulating pulmonary blood flow?
How are parasympathetics involved in regulation of pulmonary blood flow? What about sympathetics? |
Not too effective
Parasympathetics are not significantly involved in regulation of pulmonary blood flow Sympathetics have a small role **α receptor stimulation = vasoconstriction **β receptor stimulation = vasodilation |
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11. What is the major mechanical influence on overall PVR?
When is PVR lowest? What are the two classes of vessels in the lungs that PVR is altered differently in? |
Lung volume
PVR is lowest at FRC 1. Alveolar vessels -directly surround the alveoli 2. Extra-alveolar vessels (transmural vessels) -includes pulmonary arteries and arterioles connected to airways and alveolar vessels |
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12. How is the transmural pressure across alveolar vessels related to lung volume?
When is PVR increased? When is PVR decreased? |
Transmural pressure across vessels is inversely related to lung volume
PVR is increased at high lung volume **alveolar vessels are being compressed PVR is decreased at low lung volume **vessels are pulled open |
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13. How is the transmural pressure across extra-alveolar vessels related to lung volume?
When is PVR increased? What is PVR decreased? |
Transmural pressure across vessels is directly related to lung volume
PVR is decreased at high lung volume PVR is increased at low lung volume |
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14. What are the conditions at low lung volume?
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1. Low transmural pressure on extra-alveolar vessels
**PVR is increased 2. High transmural pressure on alveolar vessels **PVR is decreased |
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15. What are the conditions at high lung volume?
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1. High transmural pressure on extra-alveolar vessels
**PVR is decreased 2. Low transmural pressure on alveolar vessels **PVR is increased |
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16. In the upright lung where is PVR greatest?
How is the radii of vessels in the dependent portion? How does PVR in dependent portions compare to PVR in independent portions? |
Greater in apex (non-gavity dependent) portions versus the base (gravity-dependent) portion
Wider PVR in dependent portions is thus less than in independent portions **dealing w/ low pressure system so blood tends to flow to base of lungs (expand vessels) |
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17. What are the effects of position on PVR?
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Upright
-PVR is greatest in independent portions (apex: non-gravity dependent portion held up by surface tension) Supine -PVR greatest is anterior (ventral) portions of lungs (this is now independent portion) -Apical PVR is reversed when person is supine |
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18. What do zones integrate?
How are these related to PVR? How do the relative magnitudes of these parameters vary? |
Integrate relative magnitudes of...
1. Alveolar pressure 2. Pulmonary arterial pressure 3. Pulmonary venous pressure Significant mechanical determinants of PVR Vary in accordance w/ position of lung |
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19. How is alveolar pressure throughout the lung?
How is pulmonary arterial pressure throughout the lung? How is pulmonary venous pressure throughout the lung? |
Alveolar pressures are relatively constant throughout the lung
Pulmonary arterial pressures increase as one goes toward the base of lung (dependent portion) Pulmonary venous pressures increase as one goes toward the base of the lung **not as rapidly as pulmonary arterial pressures |
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20. Which zone is the apex of the lung (independent portion)?
How do Palv, Part, Pvenous compare? How much of the lung does this zone comprise? How is PVR and flow? |
Zone 1
Palv > Part > Pvenous Small portion of lung **increased in tall people 1. High PVR 2. Low flow |
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21. What zone is the mid region of the lung?
How do Part, Palv, and Pvenous compare? What is flow determined by in this zone? |
Zone 2
Part > Palv > Pvenous Flow determined mainly by transmural pressure across alveolar capillary |
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22. What zone is the base of the lung?
How do Part, Palv, and Pvenous compare? How is flow and resistance in this zone? |
Zone 3
Part > Pvenous > Palv 1. High blood flow 2. Low resistance |
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23. What does the prone or supine position tend to do?
What does an increased Pvenous do to blood distribution? What zone is maximized w/ an increased Pvenous? What could an increased Pvenous be a result of? What is the detrimental part of an increased Pvenous? |
Provides a more uniform blood distribution so zone 2 is maximized
More uniform distribution Zone 3 is maximized May result from mitral valve stenosis Results in pulmonary hypertension |
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24. How does exercise affect blood flow to the lungs?
How are the zones affected? Which pressures is increased? What can result do to this? |
Increases total blood flow to lungs
More blood flow in all zones Part increases Cephalization results **zone 2 moves up to zone 1; zone 3 moves up to zone 2 |
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25. As transmural pressure increases what happens to PVR?
What will increased Part and/or Pvenous due to pulmonary capillaries? How does the recruitment of non-perfused (unopened) vessels affect the number of parallel pathways? How does this affect total resistance? Besides increased Part and/or Pvenous what is another way to increase recruitment of non-perfused vessels? |
PVR falls
Will widen more pulmonary capillaries Increases the number of parallel pathways Total resistance has to go down Increased CO also increases recruitment |
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26. Does fluid accumulate in the lungs?
Why are starling capillary forces different than systemic capillaries? Solving the Starling equation, what is the net outward force? |
Fluid does not accumulate in lungs (lungs remain dry)
Due to lower plasma hydrostatic pressures There is a +1 mm Hg pressure pushing fluid into the lymphatic capillaries |
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27. What does pulmonary edema result from?
Where does fluid first accumulate? Where does it next accumulate in? What three things does pulmonary edema result from? |
Results from accumulation of fluid from capillaries
First accumulates in interstitial space (interstitial edema) Next accumulates in alveolar (alveolar edema) 1. Increased vascular permeability 2. Increased interstitial [protein] 3. Increased capillary hydrostatic pressure (due to left heart failure) |
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28. What is pleural fluid?
What are the two functions of pleural fluid? How is it removed? |
Thin layer of fluid that exists between visceral and parietal pleurae of thorax
1. Lubricates surface for movement 2. Holds lung in inflated status (surface tension) Removed by visceral lymphatic circulation |
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29. Why does excess pleural fluid (pleural effusion) occur?
What can pleural effusion do? (three things) |
Because rate of pleural fluid formation is greater than rate of removal
1. Prevent full expansion of lung 2. Reduce perfusion of lung 3. In large volumes can collapse lung |
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30. What does pleural effusion result from?
Three things |
1. Blocked lymphatics
2. Cardiac failure 3. Infection |
