Blood and immunity: pharyngeal pouch development and immunity: 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 · Blood and immunity: pharyngeal pouch development and immunity

Sample item

A newborn has tetany, a cardiac outflow tract defect and recurrent viral infections, and the chest radiograph shows no thymic shadow. Which developmental failure explains both the hypocalcaemia and the immunodeficiency?

AThird and fourth pharyngeal pouches, giving absent parathyroids and thymusBFirst and second pharyngeal arches, giving absent ear and jaw structuresCFailure of the ultimobranchial body alone, affecting calcitonin cellsDNeural crest failure affecting only the adrenal medulla

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

The answer and the reasoning

A. Third and fourth pharyngeal pouches, giving absent parathyroids and thymus

The thymus and inferior parathyroid glands arise from the third pharyngeal pouch, and the superior parathyroids from the fourth. Failure of this region in 22q11 deletion (DiGeorge syndrome) causes hypocalcaemia from absent parathyroids, T-cell deficiency from thymic aplasia, and cardiac outflow defects.

Option by option

A. Third and fourth pharyngeal pouches, giving absent parathyroids and thymus (correct)
Correct. Third and fourth pouch failure removes the parathyroid and thymic tissue.
B. First and second pharyngeal arches, giving absent ear and jaw structures
First and second arch derivatives do not give parathyroid or thymic tissue.
C. Failure of the ultimobranchial body alone, affecting calcitonin cells
The ultimobranchial body gives calcitonin-secreting cells and does not explain this picture.
D. Neural crest failure affecting only the adrenal medulla
Adrenal medulla failure would not explain hypocalcaemia or T-cell deficiency.

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.

Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is A, Third and fourth pharyngeal pouches, giving absent parathyroids and thymus. The thymus and inferior parathyroid glands arise from the third pharyngeal pouch, and the superior parathyroids from the fourth.

Why is "First and second pharyngeal arches, giving absent ear and jaw structu…" not the answer?

First and second arch derivatives do not give parathyroid or thymic tissue.

Why is "Failure of the ultimobranchial body alone, affecting calcitonin cells" not the answer?

The ultimobranchial body gives calcitonin-secreting cells and does not explain this picture.

Why is "Neural crest failure affecting only the adrenal medulla" not the answer?

Adrenal medulla failure would not explain hypocalcaemia or T-cell deficiency.

What concept does this question test?

It tests Blood and immunity: pharyngeal pouch development and immunity in Physiology. Failure of this region in 22q11 deletion (DiGeorge syndrome) causes hypocalcaemia from absent parathyroids, T-cell deficiency from thymic aplasia, and cardiac outflow defects.

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 Blood and immunity: pharyngeal pouch development and immunity?

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.