Palate Embryology — MFDS Part 1 MCQ

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HardAnatomy (Head & Neck)Palate EmbryologyMFDS Part 1

A human embryonic specimen shows elevated secondary palatal shelves contacting in the midline with a newly formed medial epithelial seam, indicating the onset of fusion rather than later seam removal and remodelling. At approximately which post-conceptional week is this finding most characteristic?

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Correct answer: E — Ninth week

The correct answer is **A, the ninth week**. The shelves of the secondary palate initially grow vertically beside the tongue, then elevate and approach one another. Midline contact and formation of the medial epithelial seam mark the onset of fusion around Carnegie stage 23, approximately the ninth post-conceptional week. Fusion is a process rather than an instantaneous event and may continue into weeks 9–10 as the epithelial seam disappears and mesenchymal continuity develops. The sixth and seventh weeks are too early, when shelf growth and repositioning predominate. The tenth week may show continuing fusion or remodelling but is not the characteristic onset. The twelfth week is too late for initial shelf contact.

Reference: Mulder PP et al. Timing of Secondary Palate Fusion in Human Embryos and Fetuses. Birth Defects Research. 2026;118(2):e70029. https://pubmed.ncbi.nlm.nih.gov/41656184/