Renal physiology: practice question

A Physiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Physiology · Renal physiology

Sample item

Where is the largest fraction of filtered sodium reabsorbed?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. Proximal convoluted tubule

About two-thirds of filtered sodium and water is reabsorbed in the proximal tubule, together with nearly all glucose and amino acids. The loop of Henle takes about 25%, the distal tubule about 5% and the collecting duct a few percent, finely regulated by aldosterone.

Option by option

  • A. Distal convoluted tubule

    The distal tubule reabsorbs only a small share, regulated by the thiazide-sensitive cotransporter.

  • B. Collecting duct

    The collecting duct handles a small amount but is where aldosterone fine-tunes sodium balance.

  • C. Proximal convoluted tubule (correct)

    Correct. Roughly 65% of the filtered load is taken up here, isotonically with water.

  • D. Thick ascending limb

    The thick ascending limb reabsorbs about a quarter, not the largest share.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is C, Proximal convoluted tubule. About two-thirds of filtered sodium and water is reabsorbed in the proximal tubule, together with nearly all glucose and amino acids.

Why is "Distal convoluted tubule" not the answer?

The distal tubule reabsorbs only a small share, regulated by the thiazide-sensitive cotransporter.

Why is "Collecting duct" not the answer?

The collecting duct handles a small amount but is where aldosterone fine-tunes sodium balance.

Why is "Thick ascending limb" not the answer?

The thick ascending limb reabsorbs about a quarter, not the largest share.

What concept does this question test?

It tests Renal physiology in Physiology. The loop of Henle takes about 25%, the distal tubule about 5% and the collecting duct a few percent, finely regulated by aldosterone.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Renal physiology?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.