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Loop of Henle and Vasa Recta

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Loop of Henle and Vasa Recta

Postby snezka18 » Sat May 07, 2011 10:04 am

I am a bit confused...what is the connection between loop of henle and vasa recta, doesnt vasa recta take away the NaCl and probably needs to take water as well...its weird it provides the blood and it also drains the blood...
Where is the sense in that? what kind of role do the solutes and water play in this? Why are the loop of henle and vasa recta collaborating?

I would appreciate any sensible information :)
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Postby Babybel56 » Sat May 07, 2011 3:06 pm

On the descending loop the vasa recta removes NaCl and urea from the Loop of Henle whilst donating water back (about 20% of reabsorbed water has it done here). This creates a high Na+ concentration where it's needed in the medulla of the kidney for the collecting ducts later.
On the ascending loop very little water is allowed back in because the walls are impermeable, so the high concentration of solutes in the Loop is maintained despite the increasing concentration of water in the interstitial space around it. However it also has many active channels for taking up the sodium, potassium and others to increase the concentration even further. However it's also important to note that because no water can get out either this solution can become quite dilute, and it's through this mechanism that we control the dilution of urine.

Hope this helps :)
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Re: Loop of Henle and Vasa Recta

Postby snezka18 » Wed May 11, 2011 5:55 pm

Hehe i kinda still dont understand, as I though descending loop of henle is permeable to water and it looses water and the water probably goes into the vasa recta? so how would that be possible that vasa recta then looses the salt? or does loop of henle donate the water to medulla so vasa recta that has the salt, follows the low osmolality of the medulla? it is very tricky...
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Postby Babybel56 » Wed May 11, 2011 6:07 pm

Sorry I was a little unclear on the first bit! As the solution descends the loop of henle it loses water to the vasa recta, causing its concentration to rise to meet the very hypertonic osmolarity of the interstitial fluids in the renal medulla (so it gets concentrated and stays that way).
In the ascending loop the membrane is impermeable so water cannot get in, but there is an active reabsorption of ions like Na+, K+ and Cl- meaning that the solution gets steadily more dilute towards the distal convoluted tubule.

Important points here: medulla always has a high osmolarity. Vasa recta keeps salts often due to an active process rather than just diffusion.
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