Achiever SNS Test 2 Problem #30

[shane.]

---

Members do not see this ad.

How does the reabsorption of solutes such as NaCl and Urea in the lower portions of the loop of Henle (which causes the osmolarity of the interstitial fluid to increase) help prevent water loss from the nephronic filtrate?

Will this not result in quite the opposite?

The way I can see this being described is that later on in the loop of Henle or even the distal convuluted tubule, that these solutes (wastes, mostly) are actively transported back into the filtrate allowing the passive resabsorption of water in the collecting duct.

Show off your knowledge of excretion.

You know you've been waiting for a thread to showcase your skills.

 

[Flipper405]

We just talked about this Friday and today in Bio class.
Urea isn't reabsorbed in the loop of Henle, it's secreted.
Urea is reabsorbed from the collecting duct.
The reabsorption of the urea (which occurs in the inner medulla where the duct is urea-permeable) increases the concentration outside of the collecting duct, which pulls water into the interstitial fluid through osmosis.

Also, NaCl is only reabsorbed on the way back up the loop (passive transport in the lower medulla, active transport in the upper medulla), which allows for the osmolarity to decrease before passing through the distal tubule.


The overall point is, water is constantly removed through osmosis in the hypertonic medullary sections of the nephron or blocked from being secreted in the less concentrated renal cortex.

 

[Flipper405]

Double post *oops*