Where is the most water reabsorbed in the kidney?

[383]

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One source says the proximal convoluted tubule, another the descending limb of the loop of Henle... anyone have a definitive answer?

 

[LianaStan]

I was taught the proximal convulated tubule is where most of the water absorption occurs. Most of the filtrate reabsorption takes place here too. The diluted filtrate that goes into the descending loop is concentrated as water is also reabsorbed, but the absolute amount of water reabsorbed here is less.

 

[gtbROX]

Hmm, I would say that it is reabsorbed most in the descending limb since water can't be actively transported out, and it relies on the progressively higher osmolarity (from Na being exported out of the other tubule) as the tubule goes down into the medulla.
http://www.youtube.com/watch?v=cc8sUv2SuaY
He explains it pretty well.