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circulation calculations - please help!!

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circulation calculations - please help!!

Postby open fire » Mon Mar 07, 2005 1:45 pm

HIya,

I have this to do for school, but I'm really confused about it, so I was wondering if someone could help me.

This is the question:
----------------
The total blood output from both ventricles was 10.08 litres per min.
The aorta leaving the left ventricle had a mean diameter of 2 cm.
40% of the blood passing thjrough the aorta went to the skeletal muscles.
The maximum blood pressure in the aorta was 160 mm Hg.
Volume of a cylinder = (pi) x r(squared) x h
Circumferance of a cirle = 2 x (pi) x r
Area of a circle = (pi) x r(squared)
1 ml = 1 cubic cm
In a cylinder, velocity = volume per unit time / cross sectional are
(pi) should be approximated to 3

Q1) What volume of blood goes to lungs every minute?

Q2) Ignoring the blood lost from the aorta into the coronary circulation, what is the mean velocity of blood per second in the aorta?
----------------

I would appriciate any help anybody could give me!

Also, what does 160 mm Hg actually mean?

Thank you!!

Jaclyn
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Postby mith » Mon Mar 07, 2005 6:59 pm

This is a fluid physics problem,not really biology....
I think 160mm Hg is the standard pressure. It means how high the mercury would go in a barometer.
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Postby MrMistery » Mon Mar 07, 2005 8:14 pm

You might be surprizes mithrilhack but in my country at the national olympics of biology you get problems like that.
By the way, I tried to solve that think bot i got bored and abandoned it. It's really hard :D :D
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Postby mith » Mon Mar 07, 2005 10:22 pm

eh, seems more of a "plug and chug" problem, I mean you have the formulas and all that.
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Postby MrMistery » Tue Mar 08, 2005 8:49 pm

that's what i said when i saw the things we had to solve at last year's national.. :D :D
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where do you have problem???

Postby 2810712 » Wed Mar 09, 2005 12:36 pm

Oh common lets try to solve his /her difficulty. and open fire , tell us which is the point you donit understand. Then you will get what U want in less time. :)

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Postby mith » Wed Mar 09, 2005 8:41 pm

okey for the first question 40% of the blood went to the skeletal muscles so does that mean the remaining 60% went to the lungs? If so then the answer is 60% of 10.08 litres.

Q2 : (10.08 Liters/Minute)/ 3*1(squared) cm(squared)= 10.08/3 liter*centimeters/ minute.
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Postby 2810712 » Thu Mar 10, 2005 9:45 am

For 1st- I also thought the same way, but it doesn't seem-practically possible, we have many more important organs other than these two, but what's the ans. then???

For 2nd- ya thats correct, have they given the max pressure to misguide students???
Also, the word mean velocity is used , I think the volume / time given is itself a mean of its values so we needn't worry about it, but still have to remember that this is a mean.
And open fire ask if you don't understand.

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Oh no

Postby 2810712 » Thu Mar 10, 2005 9:55 am

Oh no, I have got a problem
for Ist - The volume / time is given for BOTH ventricles , then should we make its half to get output from right ventrical???

for 2nd- I think the velocity of blood will not solely depend upon its input rate [input into aotra , output from ventricle!] , it will also depent upon the output of blood from aorta into arteries , Thats why , I think , pressure is given,
smaller outlet will reduce the velocity of blood in aorta [ but increase it in the artery ] So, the minimum velocity of blood in aorta corresponds to maximum pressure in aorta, isn't it. But, how to get the mimimum velocity ??? P= F/A.................................................

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Postby mith » Thu Mar 10, 2005 8:17 pm

But doesn't all the blood that goes out from the heart go thru the aorta?
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Postby MrMistery » Thu Mar 10, 2005 9:11 pm

These calcaulations are beyond my intelect but, to answer your question mithrilhack, NO!
When the ventricules of the heart contract the shoot blood into the arteries. The right ventricule shoots blood filled with CO2 into the pulmonary artery. The left ventricle shoots blood loaded with oxygen into the aorta.
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Andrew
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Postby mith » Fri Mar 11, 2005 5:29 am

doesn't sound that hard, but yeah, there seems to be alot of info missing.
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