Question

at the arterial end of a capillary, the blood pressure is high but the salt concentration of blood is low. However at the venous end the blood pressure is low, but the salt concentration is high.

a) why is the blood pressure higher at the arterial end than at the venous end?
b)why is the salt concentration higher at the venous end than at the arterial end?
c)what part do these differences play in the formation and movement of tissue fluid?

Answer 1

Umm....I havent learned this in school yet, sorry, i would help if i could, but i dont understand it, sooo sorry :(

Answer 2

OK.

Fluid pressure is placed on the blood by the vessel walls and by the heart which essentially pushes blood through the vasculature like a pump pushes water through plumbing pipes. The pressure from the heart is highest in vessels closest to the heart. That means, essentially, that it is always higher on the arterial side of circulation than on the venous side.

The concentrations of all metabolites differ on the venous and arterial end of a circulatory circuit because cells absorb molecules they need from the blood and expell into it molecules they want to get rid of.

There are quite a few physiologic nuances that I am glossing over to do with the actual mechanisms and signalling pathways, but the thing to remember is that all molecules flow down their concentration gradients. With a higher concentration of dissolved molecules on the venous side of circulation and lower fluid pressure pushing molecules out of circulation, more water molecules diffuse into venous vessels than into arterial ones.

Clear?

Answer 3

does this answer all three questions

Answer 4

It seems like you dont really understand the answer?

Answer 5

Depends on what you mean by 'answer' but yes, it touches on all three. First paragraph deals with pressure. Second paragraph deals with blood composition. Third paragraph deals with effect of both on flow down concentration cradients.

If it is not clear to you, please ask for more!

Answer 6

the first paragraph sounds like it applies to the a part of the question

Answer 7

Yes, the paragraphs deal with parts a, b and c of the question in that order...

Answer 8

i dont understand the second paragraph how is it related to salt concentration

Answer 9

OK, salt is a metabolite. Instead of talking specifically about salt, I talked about all the other molecules which get into the bloodstream as well.

Answer 10

how does last paragraph relate to c)

Answer 11

When the pressure is high in vessels (as happens with arteries but not veins), it is really really hard for more water molecules to diffuse into them. It is like trying to squeeze yourself on a train in the underground which is already packed. Similarly, fluid molecules will only diffuse down their concentration gradients - so they will only diffuse into vessels when there is a high concentration of non-water molecules inside them.

Clearer?

Answer 12

yes