Countercurrent and concurrent exchanger?

[sameeralord]

Hello everyone,

I searched the net but I don't understand the difference.

BLO0D FLOW ---------------------------------->
0% .......… saturation
0% .......… saturation
WATER FLOW <-------------------------------

Countercurrent

BLO0D FLOW ---------------------------------->
0% .......… saturation
100%........… saturation
WATER FLOW --------------------------------->

Concurrent

I understand how equilibrium would be reached in concurrent but I don't understand how counter current maintains a concentration gradient. Please explain in simple language. Also if you can explain the above diagrams, I got it from net I don't understand them much. Thanks

 

[Andy Resnick]

Those diagrams don't make too much sense...maybe the concurrent (simple exchange), but the countercurrent should look like:

BLOOD ----------------->
0%---------------> 90%
10%-------------> 100%
WATER <-----------------

It's clear from the above that along the length of the tubes, there is flow from the higher to the lower.

Now, in the kidney, the tubes form a loop, with high osmolarity in the medulla:

->600 mOsm-------->1200 mOsm----------->600 mOsm--->

And this allows for the supply of blood to the medulla without altering the high osmolarity of the medulla (which would abolish the urine concentrating mechanism).

The mechanism of the countercurrent multiplier refers to the active transport of salt out of the loop of Henle into the vasa recta. This amplifies the small gradient between the limbs to create a large gradient along the length of the limb of the loop.

 

[sameeralord]

Those diagrams don't make too much sense...maybe the concurrent (simple exchange), but the countercurrent should look like:

BLOOD ----------------->
0%---------------> 90%
10%-------------> 100%
WATER <-----------------

It's clear from the above that along the length of the tubes, there is flow from the higher to the lower.

Now, in the kidney, the tubes form a loop, with high osmolarity in the medulla:

->600 mOsm-------->1200 mOsm----------->600 mOsm--->

And this allows for the supply of blood to the medulla without altering the high osmolarity of the medulla (which would abolish the urine concentrating mechanism).

The mechanism of the countercurrent multiplier refers to the active transport of salt out of the loop of Henle into the vasa recta. This amplifies the small gradient between the limbs to create a large gradient along the length of the limb of the loop.

Thanks a lot for the response Andy Your answer is just what I need but I'm finding it difficult to understand.

0%---------------> 90%
10%-------------> 100%

Could you please tell me how to get those values and what is this the percentage of? Please excuse my poor understanding in this area.

 

[Andy Resnick]

The numbers are placeholders; the material I referred to draws an analogy with thermal transport. Silbernagl and Despopoulos "Color Atlas of Physiology" (Thieme) is as close to an ideal reference as I have seen.

 

[sardar]

Countercurrent and concurrent exchangers are two different types of heat or mass exchangers used in various industrial and biological processes. Both of these systems involve the transfer of a substance (such as heat or a solute) between two streams flowing in opposite directions. The key difference between the two is the direction of flow of the two streams.

In a countercurrent exchanger, the two streams flow in opposite directions, as shown in the diagram. This allows for a continuous and efficient transfer of the substance between the two streams. As the streams flow in opposite directions, the concentration or temperature gradient between them is maintained, allowing for a higher rate of transfer. This is because the substance in the first stream is always in contact with a stream that has a higher concentration or temperature, leading to a higher driving force for the transfer.

On the other hand, in a concurrent exchanger, both streams flow in the same direction, as shown in the diagram. This can also lead to efficient transfer, but the concentration or temperature gradient between the two streams decreases as the transfer occurs. This means that the transfer rate may decrease over time, as the driving force decreases.

To summarize, countercurrent exchangers maintain a higher concentration or temperature gradient between the two streams, leading to a more efficient transfer, while concurrent exchangers may have a decrease in the driving force over time. Both types of exchangers have their own advantages and are used in different applications depending on the specific needs of the process.