Medullary Interstital Fluid in Loop of Henle - its importance...?

[Transformers]

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I am a little confused about the importance of the medullary insterstitial fluid and its role in -countercurrent exchange/countercurrent multiplier. I am not sure about its importance with relevance tot he vasa recta and why concentrated insterstitial osmolarity in the medulla is important to kidney function.

Thanks for the clarification.

 

[Charles_Carmichael]

I am a little confused about the importance of the medullary insterstitial fluid and its role in -countercurrent exchange/countercurrent multiplier. I am not sure about its importance with relevance tot he vasa recta and why concentrated insterstitial osmolarity in the medulla is important to kidney function.

Thanks for the clarification.

It's extremely important to kidney function. If the interstitial fluid wasn't very concentrated, how would you bring water back from the collecting duct? Water is reabsorbed through passive transport from the collecting duct. Without the presence of this highly concentrated ISF, water wouldn't be pulled back into the interstitium from the collecting duct.

Without a concentrated ISF, you cannot make concentrated urine since you won't be able to reabsorb water at the collecting duct. So you just produce massive amounts of urine everyday. It'll basically be like having diabetes insipidus (where you lack ADH and thus, can't reabsorb water at the collecting duct) since the lack of a gradient means that no water will be reabsorbed. So, without the concentrated ISF, you'd be producing massive quantities of dilute urine; you'll be constantly thirsty/dehydrated; it would basically be the suck!

Hope this helps.