Countercurrent or two soute system in Schuam's?

[boomboom2dolla]

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In Schuam's review there is the countercurrent and a slightly modified version of that (2 solute) for the renal mechanism.
Do I just go with the countercurrent?
Also, how is it that the distal tubule is hypoosmotic but yet water diffuse out into the surrounding tissue, what causes it to do so?

 

[peyman2002]

for ur second question, I think the reason is that the distal tubule is permeable to Na thus Na diffuses out making the interstitial environment hyperosmotic thus water diffuses out.