drhouse
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In RS, most of the resistance is produced by 1st and 2nd bronchi, while in CVS most of the resistance is produced by arteriole.....
isn't it contradictory even though equation for both is same.
R=1/r4
pl through some light on it...
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| paganini
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Good question. There are 2 reasons of why resistance in the respiratory system arises in the medium sized bronchi and not in the smaller bronchioles.
1) Airflow in the normal lung is not laminar but turbulent(from mouth to bronchioles), thus where flow is highest(1st and 2nd bronchi) resistance is dependent mainly on flow rates. If you still don't understand this one, revise Reynolds number and you'll see that a turbulent flow produces more resistance.
2) The caliber of peripheral airways is quite small but repetitive branching creates a very large number of small airways arranged in parallel, their resistance adds reciprocally, do you remember the concept of total resistance is less than individual resistances in a parallel circuit?
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| drhouse
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thanks paganini,
i got yr point about RS but, dont u think turbulence would be more in aorta and similar to RS arteriole and capillary divide in parallel circuit so it should decrease the resistance... which is not occurring here
wot do u think
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| paganini
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The normal aorta has a laminar flow. And capillaries are not the same as arterioles. Arterioles resistance is regulated by PANS(you have smooth muscle), and yes, capillaries would be similar to bronchioles where resistance is low due to larger cross-sectional area, arrangement in parallel(a capillary is in parallel woth another capillary but in series with arteioles and venules). The large cross-sectional area also implies low velocity(inversely proportional) and low velocity favors a laminar flow.
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| paganini
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Sorry I mean SANS not PANS.
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| drhouse
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thnks paganini,
i think its sufficient
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