Possibe mistake from TPR - Kidney

[5words]

I believe TPR chose the wrong answer here so just wanted to confimr @aldol16 or anyone else can chime in:

In which region(s) of the nephron is the urine hypertonic compared to plasma?
I. Descending limb of the loop of Henle
II. Upper part of thick ascending limb of the loop
of Henle
III. The collecting duct in the presence of ADH
A. I only
B. II only
C. I and III only
D. I, II, and III

I chose A because the collecting duct is not part of the nephron but the TPR answer is C. Tjheir explanation is ADH causes Water re-absorption in the Collecting duct as well as distal tubule, yet the distal tubule wasnt listed as one of their choices.

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[Pono_0001]

I think it's not a mistake. III is correct. Even if they did not mention distal tubule, III is still correct. It'll be wrong if they says "the collecting duct but neve the distal tubule"

 

[5words]

I think it's not a mistake. III is correct. Even if they did not mention distal tubule, III is still correct. It'll be wrong if they says "the collecting duct but neve the distal tubule"

But the collecting duct is not part of the nephron.. https://histo.life.illinois.edu/histo/lab/kidney/kidney.htm

Done lots of passage where they don't consider it part of the nephron .. the nephron juts drain into it. The question specifically asked which part of the Nephron, not kidney but nephron. .

 

[Pono_0001]

I think you're getting into the danger of overthinking here, which is one of the reason why students can get a question wrong. the definition of a nephron is a functional unit of kidney, and reabsorption of water can fall under it. But some considered it not to be part of nephron due to its embryonic origin. So you can say it's a gray area, but most textbooks talk about collecting duct as part of nephron. Honestly I don't see the distinction as important as you don't ever see collecting duct not mentioned or drawn in diagram's of nephron. Unless there's an MCAT standalone question asking you if collection duct is part of the nephron. In that case good luck lol


EDIT: The book here also echos what I just said. Distal nephron often include collection duct due to the collecting duct working with the other tubules as a functional unit:
Amazon product

 

[5words]

I think you're getting into the danger of overthinking here, which is one of the reason why students can get a question wrong. the definition of a nephron is a functional unit of kidney, and reabsorption of water can fall under it. But some considered it not to be part of nephron due to its embryonic origin. So you can say it's a gray area, but most textbooks talk about collecting duct as part of nephron. Honestly I don't see the distinction as important as you don't ever see collecting duct not mentioned or drawn in diagram's of nephron. Unless there's an MCAT standalone question asking you if collection duct is part of the nephron. In that case good luck lol


EDIT: The book here also echos what I just said. Distal nephron often include collection duct due to the collecting duct working with the other tubules as a functional unit:
Amazon product

I kid you not, i am seriously trying to understand here or i wouldn't be posting on this forum, TPR doesn't consider the collecting duct to be part of the neprhon, it;s either that or i am confusing nephrons with renal tubule. Confirmation bias , i suppose, but it seems as if most people would agree that collecting duct are part of the kidney.. Already wasted one hour thinking about whether it was the tubule, or the kidney. And wikipedia, isn't making my life easier as well.
idk, but those sentence seems to be contradicting each other:

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Also, i was taught at school that nephrons are part of the kidney, so i wouldnt made the chnage had i not encounter a question, which specifically asked "Which wasnt part of Nephron or Tubule" and the collecting duct was the right answer. OR i wouldn't have made the change, or maybe i am confusing Renal tubule with nephrons?? but it seems like you are right, so the question is right indeed... Still need to double check whether or not the Collecting duct is part of the Tubule, its either that or nephron... I would appreciate if you could help me understand .

 

[Pono_0001]

I'd say it's one of those things that either case can be correct depending on whoever wrote the question. From an embryological point of view then collecting duct is not part of a nephron. from a functional point of view, then it is. but the renal physiology book is a review book for Step 1, so I'd imagine MCAT is more likely to take a similar stand. But either way, just know that it's a gray area and proceed with caution if you do see a qusetion on this

 

[desperadoflakes]

In the descending limb you're reabsorbing a ton of water into the plasma, but you haven't reabsorbed very much solute yet (that happens in the ascending limb). So the plasma will be very dilute, which means that the urine will be hypertonic to it. Same deal for ADH in the collecting duct - the aquaporins will cause lots of reabsorption of water, which means the plasma will be diluted, so the urine will be hypertonic relative to the plasma. B doesn't work because the ascending limb is where you reabsorb a ton of salt.