Does rate of blood flow across capillaries slow?

[Turkelton]

I understand that blood pressure drops as it goes from aorta-arteries-arterioles-capillaries-venules etc, but I was wondering does the rate of blood flow decrease as well as blood flows across the capillary beds?? And if the flow of blood does decrease across capillary beds, what happens to the back traffic? Do the arterioles and arteries vasodilate to compensate?
As always thanks in advance.

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[AZFutureDoc]

Depends on how you look at it. Hopefully, you know from physics that the thinner the radius, the faster the flow, and this would be true if 1 vein turned into 1 artery. But 1 vein branches off, so velocity actually slows. If you were to add up the volume of all the capillaries, they would hold more volume than a single vein, so the velocity slows.

 

[Turkelton]

Thanks for the response on flow rate. I thought it would help me answer a TPR Blood Volume question, but I'm not sure If I still understand.

The question involves a diagram with "Volume of blood flow" on the Y-axis and "Aorta-Arteries-Arterioles-Capillaries-Venules-Veins-Vena Cava" on the X-axis for the answer would I:

A) See a straight horizontal line across, indicating that blood volume is flowing at the same rate across all the vessels.

or

B) See a line that gradually descends from the Aorta to the Capillaries and then rises again from capillaries to venules to veins to Vena Cava.

Thanks again. Also is blood pressure lower in the capillaries or in the veins?

 

[Phlame217]

yes you may think of it as above...

But cappilaries themselves are regulated by openning and closing branches within which can raise pressure or lower pressure just enough to increase adsorbtion such as in the kidneys.

 

[Turkelton]

I'm not sure if I catch your drift phlame. Do you think the answer is A or B? Thanks.

 

[engineeredout]

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Thanks again. Also is blood pressure lower in the capillaries or in the veins?

Veins.

 

[Vihsadas]

Thanks for the response on flow rate. I thought it would help me answer a TPR Blood Volume question, but I'm not sure If I still understand.

The question involves a diagram with "Volume of blood flow" on the Y-axis and "Aorta-Arteries-Arterioles-Capillaries-Venules-Veins-Vena Cava" on the X-axis for the answer would I:

A) See a straight horizontal line across, indicating that blood volume is flowing at the same rate across all the vessels.

or

B) See a line that gradually descends from the Aorta to the Capillaries and then rises again from capillaries to venules to veins to Vena Cava.

Thanks again. Also is blood pressure lower in the capillaries or in the veins?

I think you'll have to post the entire question because what you've posted can be interpreted two different ways, and depending on the interpretation, you get a different answer.

If the questions asks, "What would the graph look like if you considered volume of blood flow per time across all arteries arterioles capillaries venules veins?". In that case, you must remember that total flow is constant at any point in the circulation.

Think of it this way. All of the blood that leaves the aorta has to end up in the arteries, and all of the blood that leaves the arteries has to end up in the arterioles and so on and so forth. If the flow were not the same from all of the arteries to all of the arterioles, then you would necessarily have to have a build up of blood pooling somewhere in the circulation.. Flow in must = flow out otherwise your loosing blood somewhere along the way.

Now, if the question asked, "What would the graph look like if you considered the volume of blood flow per unit time from one artery to one ateriole to one capillary?" and so on and so forth, then flow would decrease toward the capillary. It would be a descending function until the level of the capillary, and then would ascend until you reached the vena cavae.

Do you see why?

My intuition tells me that the question is trying to test your understanding of the physical concept of "total flow" in the circulatory system. They are trying to test to see if you realize that flow at any cross-sectional point in the circulation has to equal the flow from any previous point or further point; flow is constant. So, I'd pick "A".

EDIT: I take it back, from what you've posted, the plural forms 'arteries', 'arterioles', 'capillaries' etc. are being used, so I think that the question is not ambiguous and they are testing whether you understand total flow. Still answer choice A.
P.S. engineeredout is also right. 😛

 

[Turkelton]

Looking back at my original question I can see how that can be taken in two different ways, sorry about the wordiness/unclearness. I shouldn't have mentioned the word rate, since time was not an aspect of the question.

The question was indeed, about the physical constant of "total flow". I wasn't sure if total flow was constant, or if it in certain parts of the body blood flow would back up. The answer total flow certainly makes more sense. The book says the correct answer is A, but I couldn't get my head around why the answer was A, so thanks for help clarifying it everyone I do appreciate it.