Page 1 of 2: physiology respiratory system

pratik · Credits: 11374 My Scrapbook

what fraction of the alveolar air is replaced by new atmospheric air with each breath

a 1/3
b 1/5
c 1/7
d 1/10

guest · Credits: 78825 My Scrapbook My Reading List 262569 Books

Normal residual capacity is 2300 ml
Normal tidal volume is 500 ml
Normal physiological dead space is 150.
So only 350 ml reaches the lungs and mixes with 2150 (2300 - 150) ml of alveolar air.
So fraction replaced [350/(2150+350)] = 1/7 or about 14%

pratik · Credits: 11374 My Scrapbook

man u are taking Physiology to the next level

great explanation

alekhin · Credits: 2171 My Scrapbook

chand = physio guru !

manpreet108 · Credits: 30682 My Scrapbook

what IQ is the least req to grasp this problem??????
i simply dont get it.

can someone help a little more t make it comprehensible ....or should it be left as a matter beyond IQ?

guest · Credits: 78825 My Scrapbook My Reading List 262569 Books

Do not be worried, just take sometime to understand this.

During normal respiration, we breathe in and out. After breathing out there is always some air left behind in the lungs. This is known as functional residual capacity (FRC). Now this includes air in the alveoli and air in trachea (or the dead space).

On the next inspiration, fresh air enters the lungs, the amount per breath is known as tidal volume (TV). This volume dilutes the functional residual capacity volume. "Dilute" becase FRC is much more as compared to TV. To put this dilution in scientific terms we just say some FRC is replaced by TV.

Now the fraction of TV reaching alveoli is 350 ml, as 150 ml is dead volume (500 ml being normal tidal volume). It goes and dilutes 2150 ml of alveolar air(2300 ml being FRC). Total volume of air at that instant is 2150 + 350 (=2500 ml). So the fraction replaced by fresh air is simply 350/2500.

If still in doubt please do ask again.

manpreet108 · Credits: 30682 My Scrapbook

ths couldnt have been explained better!

now i get the picture clear.no doubts .

THANK YOU,SIR.

alekhin · Credits: 2171 My Scrapbook

just to complicate things

lazybonezzz · Credits: 54705 My Scrapbook

GREAT EXPLANATION CHAND
MAN I HATE THESE DIAGRAMS

manpreet108 · Credits: 30682 My Scrapbook

lb i hope u are not adressing me as 'man' as u often do...
i am not the culprit to post the diagram u hate!!

but it was good ,and pretty informative too!

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