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Hello everyone,

can somebody help me, i've red that in the early distal tubube occurs sodium reabsorption without water reabsorption because it's impermeable to water, whereas water reabsorption always follow sodium reabsorption, and if water don't reabsorp in this segment but sodium reabsorps so that the blood osmolarity is increase because no water reabsorption, i hope someone can help me solve my confusing, so from where water reabsorption when early distal tubule reabsorps sodium? thank you....


What is your source of this info?

Every single physiology book states that the maximum water reabsorption takes place in proximal tuble only, as intracellular osmolarity is increased.


i've red physiology guyton, and i don't understand because if water don't reabsorp but sodium is reabsorped in early distal tubule, the blood that leave kidney will be more hypertonic, so i have question, from where water reabsorped to balance sodium reabsorption in early distal tubule?

thanx for your reply....


My Bad!

I thought you had a doubt about proximal water reabsorption.Sorry.

well, Only salt is reabsorbed at early thick ascending loop til early DCT, not water opposite to what was happening in descending loop, to maintain hyperosmolarity in medullary intersitium, which is why it's called countercurrent Tubular fluids reaches the early distal tubule it is diluted and very lil salt is reabsorbed and that reabsorbed salt makes interstitium hyperosmolar but close to 300mos and vasa recta maintains that hyperosmolarity to isosmolarity by giving out water from capillary. So in nutshel we we have two countercurrents.1. countercurrent multiplier(making medullary hyper osmolar and 2nd vasa recta countercurrent exchange maintaining the hyperosmolarity..and later ADH plays role.

If still not clear to you, watch dr najeeb lectures.


Okay, thank you very much, now it's more clear to me, but if the vasa recta always give out the water to interstisium to balance sodium reabsorption in early DCT, so it will be liquid acumulation in interstisium, because there is no liquid reabsorption in this segment, how about this?

thanks before....

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