Good ol' Loop of Henle wants YOU!

[Lazerous]

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Why are the lower portions of loops of Henle and the collecting duct selectively permeable to NaCl, urea, and/or water?

A. To increase the osmolarity of interstitial fluid in the cortex and help prevent water loss from the nephronic filtrate
B. To decrease the osmolarity of interstitial fluid in the cortex and help promote water loss from the nephronic filtrate
C. To increase the osmolarity of interstitial fluid in the inner medulla and help prevent water loss from the nephronic filtrate
D. To decrease the osmolarity of interstitial fluid in the inner medulla and help promote water loss from the nephronic filtrate
E. No specific reason can be deduced from the said phenomenon.

The answer is C.

I understand that increasing osmolarity will make the inner medulla hypertonic but wouldn't that PROMOTE water loss from the nephronic filtrate (which is the fluid inside the nephron itself, no?) instead of prevent it?

 

[Contach]

man did a switcheroo on me.. had to edit, but double posted - sorry!

 

[Contach]

Why are the lower portions of loops of Henle and the collecting duct selectively permeable to NaCl, urea, and/or water?

A. To increase the osmolarity of interstitial fluid in the cortex and help prevent water loss from the nephronic filtrate
B. To decrease the osmolarity of interstitial fluid in the cortex and help promote water loss from the nephronic filtrate
C. To increase the osmolarity of interstitial fluid in the inner medulla and help prevent water loss from the nephronic filtrate
D. To decrease the osmolarity of interstitial fluid in the inner medulla and help promote water loss from the nephronic filtrate
E. No specific reason can be deduced from the said phenomenon.

The answer is C.

I understand that increasing osmolarity will make the inner medulla hypertonic but wouldn't that PROMOTE water loss from the nephronic filtrate (which is the fluid inside the nephron itself, no?) instead of prevent it?

You changed your post 😛

The lower portions of the Loop of Henle = the bottom of the ascending and descending limbs. these are in the adrenal cortex. Here's an interesting fact for you. Birds have an extraordinarily long loop of henle. This allows them to create concentrated urine by creating a large gradient in the adrenal cortex. Thus more water from the collecting duct will be reabsorbed by the surrounding interstitial fluid of the adrenal cortex. This gives the ability of birds to piss out a very concentrated urine of uric acid (which I think is that white stuff that is a bitc# to get off your car). It gives them the amazing ability to retain water.

If you remember chem: O = MRTi, where M is concentration. If you are increasing the concentration of the interstitial fluid (the area surrounding the collecting duct and lower loop of henle) then you are increasing osmolarity.

I hope this helps you understand a very vital organ in our body. I would say the answer is A because I thought it is in the cortex. But apparently it's C - good to know!

No, you increase the osmolarity of the surrounding fluid, thus increasing the particle content, and the water leaves the collecting duct and goes into the interstitial fluid. Therefore you are making urine more concentrating, you are reabsorbing more water, and you are promoting the loss of water from the nephronic filtrate ( you are correct - this is the fluid within the nephron).

 

[Lazerous]

You changed your post 😛

The lower portions of the Loop of Henle = the bottom of the ascending and descending limbs. these are in the adrenal cortex. Here's an interesting fact for you. Birds have an extraordinarily long loop of henle. This allows them to create concentrated urine by creating a large gradient in the adrenal cortex. Thus more water from the collecting duct will be reabsorbed by the surrounding interstitial fluid of the adrenal cortex. This gives the ability of birds to piss out a very concentrated urine of uric acid (which I think is that white stuff that is a bitc# to get off your car). It gives them the amazing ability to retain water.

If you remember chem: O = MRTi, where M is concentration. If you are increasing the concentration of the interstitial fluid (the area surrounding the collecting duct and lower loop of henle) then you are increasing osmolarity.

I hope this helps you understand a very vital organ in our body. I would say the answer is A because I thought it is in the cortex. But apparently it's C - good to know!

No, you increase the osmolarity of the surrounding fluid, thus increasing the particle content, and the water leaves the collecting duct and goes into the interstitial fluid. Therefore you are making urine more concentrating, you are reabsorbing more water, and you are promoting the loss of water from the nephronic filtrate ( you are correct - this is the fluid within the nephron).

SEE! You and I are agreeing on the same thing. I appreciate how you brought gen chem into this to better help me understand how an increase in osmolarity means an increase in solute concentration with in turn means we are hypertonic in the interstitial fluid. BUT as you said this should PROMOTE water loos from the nephronic fluid however choice C says it it PREVENTS water loss.

That's the part I am confused on...

 

[Contach]

yeah that's f'ed up man. Where is this question from?\
Can someone confirm that we understand this correctly?
Oh ****, I just realised I had the kidney oriented backwards.
The loop ofhenle is in the inner medulla. With that said.. I can't find a reasonable answer for this question...
I think the answer should be:
F) To increase the osmolarity of interstitial fluid in the inner medulla and help promote water loss from the nephronic filtrate

 

[211183]

Perhaps the problem is attempting to explain the following.
The descending limb is selectively permeable to mostly H20, while the ascending limb is s.p. to mostly salts and urea. This is due to the changing gradient. Therefore, as you go into the lower portions of the loop, you find that the loop switches from permeability of H20 to salts. Thus, water loss is prevented. Same goes for the collecting duct, if I am not mistaken.

Right before you reach the bottom, the water concentration in the interstitial has greatly increased, so you prevent water loss near the bottom, as salts begin to resorb back into the body.

That's the best defense I can come up with for that Q. Not sure though. Hopefully DAT questions aren't that complicated.

 

[Lazerous]

The question is from Achiever test 2.

 

[211183]

I haven't taken it yet. Acutally ... taking it tomorrow! So... I guess I may have to subtract one from my final Chem score tomorrow. 😀