Respiratory physiology: surfactant: 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 · Respiratory physiology: surfactant

Sample item

A premature neonate has grunting respiration and a ground-glass chest radiograph. Which physiological change is primarily responsible for the impaired lung mechanics?

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

The answer and the reasoning

A. Increased alveolar surface tension with reduced lung compliance

Surfactant (dipalmitoylphosphatidylcholine from type II pneumocytes) reduces surface tension. Its deficiency raises surface tension according to the law of Laplace, causing atelectasis, stiff lungs and low compliance in respiratory distress syndrome.

Option by option

  • A. Increased alveolar surface tension with reduced lung compliance (correct)

    Correct. High surface tension collapses alveoli and stiffens the lungs.

  • B. Reduced chest wall recoil only

    The problem lies in the alveoli, not in chest wall recoil.

  • C. Increased lung compliance with alveolar over-distension

    Compliance falls, not rises, in surfactant deficiency.

  • D. Decreased airway resistance with air trapping

    Airway resistance is not the primary problem and air trapping is not seen.

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 A, Increased alveolar surface tension with reduced lung compliance. Surfactant (dipalmitoylphosphatidylcholine from type II pneumocytes) reduces surface tension.

Why is "Reduced chest wall recoil only" not the answer?

The problem lies in the alveoli, not in chest wall recoil.

Why is "Increased lung compliance with alveolar over-distension" not the answer?

Compliance falls, not rises, in surfactant deficiency.

Why is "Decreased airway resistance with air trapping" not the answer?

Airway resistance is not the primary problem and air trapping is not seen.

What concept does this question test?

It tests Respiratory physiology: surfactant in Physiology. Its deficiency raises surface tension according to the law of Laplace, causing atelectasis, stiff lungs and low compliance in respiratory distress syndrome.

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 Respiratory physiology: surfactant?

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.