Term
| What advantages do the short, thin-walled, large diameter pulmonary arterial vessels convey? |
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Definition
low resistance to blood flow-->low BP in pulmonary vessels
high compliance, allowing pulmonary arteries to act as volume "buffers" for output from right heart |
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Term
| quanitit of blood flowing through lungs |
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Definition
| 5 L/min at rest (same as systemic) |
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Term
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Definition
keep pulmonary tissue alive-->nutritive circulation of non-gas-exchanging parts of lung
like rest of systemic circ, it's a high P system |
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Term
| muscle coat in arterial wall |
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Definition
| extends w/age until ~20 y.o., where it reaches arterioles adjacent to alveoli |
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Term
| fate of blood in bronchial circulation |
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Definition
1. drains back to right heart directly
2. drains to left atrium of heart
a) some gets reoxygenated, joining pulmonary blood before passing through alveolar capillaries
b) some does not get reoxygenated, joining pulmonary blood after alveoli-->that's why systemic arterial blood slighly lower O2 content than pulmonary venous blood |
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Term
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Definition
| when venous blood mixes directly w/arterialized blood in lung |
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Term
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Definition
| 450 ml, roughly 1/10 total in circ system |
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Term
| usual pressure unit of lung |
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Definition
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Term
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Definition
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Term
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Definition
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Term
| normal ventilation:perfusion ratio |
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Definition
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Term
| driving force for blood flow through the alveolar capillaries is about... |
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Definition
5 mm Hg in recumbent human at rest
**this pressure difference sufficient ot drive full CO through pulmonary capillaries-->lot of flow from a little P |
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Term
| 2 adaptations that maximize gas exhanging capability of lung |
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Definition
| large area and short diffusion path |
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Term
| diminished alveolar oxygen ____ local alveolar blood flow |
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Definition
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Term
| When concentration of O2 in alveoli decreases below normal, adjacent blood vessels ______, and vascular R ______ as much as fivefold. |
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Definition
When concentration of O2 in alveoli decreases below normal, adjacent blood vessels CONSTRICT, and vascular R INCREASES as much as fivefold.
**this is opposite of what's seen in systemic vessels
**when they vessels constrict, the blood will through areas of lung that are better aerated, providing an automatic control system for distributing blood flow to different pulmonary areas in proportion to their degree of ventilation |
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Term
| it's believed that the low O2 concentration causes some vasoconstrictor substance to be released from lung tissue, which causes constriction of small arteries. What's this mechanism referred to as? |
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Definition
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Term
| autonomic nervous contorl of pulmonary blood flow through lungs |
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Definition
| weak - vagal (parasympathetic) fibers cause slight decrease in pulmonary vascular resistance and vv for sympathetic |
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Term
| autonomic contorl of pulmonary blood volume in lungs |
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Definition
strong -->has great effect in constricting the large pulmonary capacitative vessels, esp. the veins
**gravity also exerts a strong influence over distribution of blood through pulm. circ |
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Term
CAPILLARY FLUID DYNAMICS
1. pulmonary capillary pressure is... |
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Definition
| 1. very low, about 7 mm Hg (peripheral about 17) |
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Term
| interstitial fluid hydrostatic P is... |
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Definition
| slightly more negative than epripheral tissues about -5 to -8 (caused largely by lymphatic pumping) |
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Term
| 3. pulmonary capillaries are relatively ____ to protein molecules |
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Definition
| pulmonary capillaries are relatively LEAKY to protein molecules, so that interstitial fluid has more protein and a colloid osmotic P of about 14 mm Hg (less than half that in peripheral subcutaneous tissues) |
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Term
| 4. alveolar walls are extremely... |
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Definition
| thin, and alveolar epithelium covering alveolar surfaces is so weak that if ruptured by any positive P in interstitial space greater than atmospheric, it allows dumping of fluid from iterstitial spaces into alveoli |
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Term
| forces driving fluid from capillaries into interstitium (3) |
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Definition
capillary BP, interstitial fluid colloid osmotic pressure, negative hydrostatic P in interstitium
**total outward force = 29 mm Hg |
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Term
| force driving absorption of fluid into capillaries |
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Definition
plasma colloid osmotic pressure, which is ~ 28 mm Hg
**normally net outward force, so extra is picked up by lymphatic ducts and pumped back into systemic circ |
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Term
| pulmonary edema usually caused by what 2 things? |
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Definition
1. damage to pulmonary capillary membrane caused by infections or breathing noxious substances
2. left heart failure or mitral valve disease |
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Term
| initial rise in left atrial pressure up to about _____ mmHg has virtually no effect on pulmonary capillary (peak) pressure |
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Definition
7-8 mm Hg
**any increase in left atrial P beyond this increases the capillary pressure almost as much, which begins to drive fluid out of the capillaries |
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Term
| before positive interstitital fluid P can occur and cause overt edema, what 3 factors must be overcome? |
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Definition
1. normal negativity of interstitial fluid P of lungs
2. lymphatic pumping of fluid out of interstitial spaces
3. increased osmosis of fluid into pulmonary capillaries caused by decreased protein in interstitial fluid when lymph flow increases |
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Term
| pulmonary capillary P must normally rise to a value at least equal to _____ before significant pulmonary edema will occur |
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Definition
| the plasma colloid osmotic P |
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Term
| the pulmonary capillary P must rise from teh normal level of ____ to over ____ to cause acute pulmonary edema, meaning there is a safety factor of about _____ |
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Definition
| the pulmonary capillary P must rise from the normal level of 7 mm Hg to over 28 mm Hg to cause acute pulmonary edema, meaning there is a safety factor of about 21 mm Hg |
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Term
| in chronic pulmonary edema, safety factor against pulmonary edema can rise to as high as _____, compared to normal value of 21 mm Hg in acute conditions |
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Definition
35-45 mm Hg
**when pulmonary capillary P remains elevated chronically (2+ wks), the lungs become more resistant to pulmonary edema bc the lymph vessels expand greatly, increasing their capability for carrying fluid away from interstitial spaces as much as tenfold |
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Term
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Definition
VA/Q
VA = alveolar ventilation (~5250 ml/min)
Q = CO (~5000 ml/min) |
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Term
| 2 reasons why local values for VA/Q can be considerably different from 1, even in a healthy lung |
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Definition
1. not all parts of lung get same amount of fresh air (bottom gets more and top gets less when standing)
2. local pulmonary blood flow also varies considerably from bottom to top of lungs bc pressure from bottom to top of lungs later amount of local pulmonary blood flow |
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Term
| in the upper part of the lung, pulmonary blood flows for _____ and for part of time _______ |
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Definition
in the upper part of the lung, pulmonary blood flows for PART OF CARDIAC CYCLE and for part of time IT DOES NOT FLOW
**high-pressure bonrchial circ still keeps tissue alive |
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Term
| when you reach points only ____ mm Hg above teh heart, then diastolic pulmonary pressure is sufficient to keep blood moving and so blood continues flowing throughout cardiac cycle in these lower parts of lung |
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Definition
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Term
ZONES OF WEST ("zones of the lungs")
Zone 1 blood flow |
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Definition
| systolic P never sufficient to force blood to upper parts of lungs, so NO pulmonary blood flow there-->only found when air pressure is high in lungs (trumpet, deep sea diving, right heart failure) |
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Term
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Definition
| intermittent through cardiac cycle (during diastole, P usually not enough during systole)-->present in normal lung from pt 8 mm Hg above heart to top of lungs |
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Term
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Definition
| continuous, has greatest pulmonary flow in lungs |
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Term
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Definition
still continuous but reduced bc teh shear wt of lung tissue above crushes down on this part and compresses the pulmonary capillaries, whereby reducing their blood flow
Zone 4 is a special type of Zone 3 blood flow |
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Term
| What happens when you turn the lungs sideways, as when a subject lies down? |
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Definition
| no part of lung is very far above or below heart, so essentially whole lung has Zone 3, continuous flow |
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Term
| these zones refer not to _____ parts of lung but to ____ patterns of pulmonary blood flow |
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Definition
| these zones refer not to ANATOMICAL parts of lung but to FUNCTIONAL patterns of pulmonary blood flow |
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Term
| in normal lung, ventilation per volume and pulmonary blood flow are greatest where? |
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Definition
| at base and least at apex |
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Term
| Where is the VA/Q ratio lowest and greatest in lung? Why? |
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Definition
lowest at bottom and greatest at top
bc blood flow drops off proportionately more as you move toward the apex - bc blood flow is so low at top of lung |
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Term
| What happens to VA/Q ratio when ventilation overbalances perfusion (as in pulmonary embolism)? Body's response? |
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Definition
| VA/Q greater than 1 due to too much ventilation or too little perfusion body compensates by bronchiolar constriction and arteriolar dilation opposite is true for perfusion overbalancing ventilation (body responds by bronchiolar dilation and arteriolar constriction) |
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