Histology: osteoclast differentiation: 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 · Histology: osteoclast differentiation

Sample item

Mature osteoclasts form from haemopoietic monocyte-lineage precursors. Which pair of factors from osteoblast-lineage cells is needed for this differentiation?

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

The answer and the reasoning

C. M-CSF and RANKL

Osteoblast-lineage cells secrete M-CSF, which supports precursor survival, and RANKL, which binds RANK on precursors and drives fusion into multinucleated osteoclasts. Osteoprotegerin is a decoy receptor that blocks RANKL, and denosumab mimics this action. Sclerostin and DKK1 inhibit Wnt signalling and bone formation.

Option by option

  • A. Sclerostin and DKK1

    Sclerostin and DKK1 are Wnt inhibitors that reduce osteoblast activity.

  • B. Osteoprotegerin and calcitonin

    Osteoprotegerin blocks RANKL and calcitonin inhibits mature osteoclasts, so neither promotes differentiation.

  • C. M-CSF and RANKL (correct)

    Correct. M-CSF and RANKL together drive osteoclast formation.

  • D. Osteocalcin and type I collagen

    Osteocalcin and type I collagen are bone matrix products and are not osteoclast differentiation signals.

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, M-CSF and RANKL. Osteoblast-lineage cells secrete M-CSF, which supports precursor survival, and RANKL, which binds RANK on precursors and drives fusion into multinucleated osteoclasts.

Why is "Sclerostin and DKK1" not the answer?

Sclerostin and DKK1 are Wnt inhibitors that reduce osteoblast activity.

Why is "Osteoprotegerin and calcitonin" not the answer?

Osteoprotegerin blocks RANKL and calcitonin inhibits mature osteoclasts, so neither promotes differentiation.

Why is "Osteocalcin and type I collagen" not the answer?

Osteocalcin and type I collagen are bone matrix products and are not osteoclast differentiation signals.

What concept does this question test?

It tests Histology: osteoclast differentiation in Anatomy. Osteoprotegerin is a decoy receptor that blocks RANKL, and denosumab mimics this action. Sclerostin and DKK1 inhibit Wnt signalling and bone formation.

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 Histology: osteoclast differentiation?

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.