Embryology: pulmonary hypoplasia: practice question

A Anatomy 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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Anatomy · Embryology: pulmonary hypoplasia

Sample item

A newborn with bilateral renal agenesis, low-set ears and flattened facies has severe respiratory failure and small lungs at autopsy. What is the explanation for the lung findings?

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

The answer and the reasoning

C. Oligohydramnios compresses the thorax and restricts lung growth

Fetal urine is the main source of amniotic fluid in the second half of pregnancy. Renal agenesis causes oligohydramnios, producing Potter sequence with compressed chest, limited fetal breathing movements and pulmonary hypoplasia. The respiratory failure is not due to a hernia or fistula.

Option by option

  • A. Defect in the pleuroperitoneal membrane

    A defect in the pleuroperitoneal membrane causes a diaphragmatic hernia.

  • B. Failure of the tracheoesophageal septum

    A tracheoesophageal septal defect gives a fistula and does not cause small lungs.

  • C. Oligohydramnios compresses the thorax and restricts lung growth (correct)

    Correct. Oligohydramnios and thoracic compression restrict lung development.

  • D. Absent surfactant genes

    Absent surfactant genes cause respiratory distress with normally sized lungs.

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 Anatomy question

What is the answer to this Anatomy question?

The best answer is C, Oligohydramnios compresses the thorax and restricts lung growth. Fetal urine is the main source of amniotic fluid in the second half of pregnancy.

Why is "Defect in the pleuroperitoneal membrane" not the answer?

A defect in the pleuroperitoneal membrane causes a diaphragmatic hernia.

Why is "Failure of the tracheoesophageal septum" not the answer?

A tracheoesophageal septal defect gives a fistula and does not cause small lungs.

Why is "Absent surfactant genes" not the answer?

Absent surfactant genes cause respiratory distress with normally sized lungs.

What concept does this question test?

It tests Embryology: pulmonary hypoplasia in Anatomy. Renal agenesis causes oligohydramnios, producing Potter sequence with compressed chest, limited fetal breathing movements and pulmonary hypoplasia. The respiratory failure is not due to a hernia or fistula.

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 Embryology: pulmonary hypoplasia?

Learn every nerve by its route, its muscles and what a lesion looks like at the bedside. That one habit answers a large share of questions. Then use the flashcards and the other Anatomy 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.