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Blood flow rate vs pressure
- Thread starter dahmsom
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You were correct on the law of continuity. A1V1 = A2V2. If you increase the area the velocity will decrease, but the flow rate will remain constant. If you took this same "tube" and constricted it to a more narrow section then the velocity would increase while maintain the original flow rate. (*note* The equation addresses area and volume, but my explanation mentions velocity. I didn't want to confuse you with my terminology and the equation.)
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I'd like more info on this, the question only says "through the capillaries" and then asks about volume. That could mean the volume of blood flow through every capillary in the entire body, or it could mean through a randomly chosen section of capillaries. The term "volume" by itself will change depending on if we are talking every capillary in the body, or just one capillary.
In any case, I was under the impression that the pressure gradually drops as one follows the arteries away from the heart. So by the time we reach capillaries, in say the nail bed matrix, the pressure is much lower, and the capillaries themselves are about the width of a red blood cell, give or take. So if you are comparing a single capillary to a single artery, It would definitely suggest that the volume per unit time is much lower in the capillary, given the size constraint alone, nevermind the pressure.
We can play word games and say that "capillaries" = 2. One, two, or ten capillaries, with unknown length, would surely hold less blood volume (and you would think it would flow less total volume) than an artery near the heart.
Same with veins, you can see a person standing still will pool blood in the veins, the total volume flow would be near zero if they remain standing motionless, since there is no blood pressure to push blood up a vein of the leg for instance. veins of the neck on the other hand have gravity. Based on this alone I would avoid the answer choices having anything to do with veins and volume/time blood flow.
In any case, I was under the impression that the pressure gradually drops as one follows the arteries away from the heart. So by the time we reach capillaries, in say the nail bed matrix, the pressure is much lower, and the capillaries themselves are about the width of a red blood cell, give or take. So if you are comparing a single capillary to a single artery, It would definitely suggest that the volume per unit time is much lower in the capillary, given the size constraint alone, nevermind the pressure.
We can play word games and say that "capillaries" = 2. One, two, or ten capillaries, with unknown length, would surely hold less blood volume (and you would think it would flow less total volume) than an artery near the heart.
Same with veins, you can see a person standing still will pool blood in the veins, the total volume flow would be near zero if they remain standing motionless, since there is no blood pressure to push blood up a vein of the leg for instance. veins of the neck on the other hand have gravity. Based on this alone I would avoid the answer choices having anything to do with veins and volume/time blood flow.
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