Renal and acid–base: renal medullary hypoxia: 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 and acid–base: renal medullary hypoxia

Sample item

After prolonged hypotension, which tubular segment is most vulnerable to ischaemic injury?

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

The answer and the reasoning

C. Outer medullary thick ascending limb and proximal straight tubule

The outer medulla has a low oxygen tension because the countercurrent arrangement of the vasa recta shunts oxygen, and the thick ascending limb and proximal straight tubule do a lot of oxygen-dependent transport work. They are therefore the first to suffer in hypoperfusion, causing acute tubular necrosis.

Option by option

  • A. Papillary thin descending limb

    The thin descending limb has minimal active transport and a low oxygen demand.

  • B. Glomerular capillary tuft

    The glomerular tuft has a high flow and no major transport work.

  • C. Outer medullary thick ascending limb and proximal straight tubule (correct)

    Correct. High transport work with a low oxygen supply makes these segments vulnerable.

  • D. Cortical collecting duct

    The cortical collecting duct has a lower oxygen demand and a better supply.

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, Outer medullary thick ascending limb and proximal straight tubule. The outer medulla has a low oxygen tension because the countercurrent arrangement of the vasa recta shunts oxygen, and the thick ascending limb and proximal straight tubule do a lot of oxygen-dependent transport work.

Why is "Papillary thin descending limb" not the answer?

The thin descending limb has minimal active transport and a low oxygen demand.

Why is "Glomerular capillary tuft" not the answer?

The glomerular tuft has a high flow and no major transport work.

Why is "Cortical collecting duct" not the answer?

The cortical collecting duct has a lower oxygen demand and a better supply.

What concept does this question test?

It tests Renal and acid–base: renal medullary hypoxia in Physiology. They are therefore the first to suffer in hypoperfusion, causing acute tubular necrosis.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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 and acid–base: renal medullary hypoxia?

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.