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Pathology · single question

A patient presents with a cleft lip. The embryological failure responsible is:

  1. Failure of neural crest cell migration into the frontonasal process
  2. Failure of fusion of the two lateral palatine shelves
  3. Failure of fusion of the maxillary prominence with the medial nasal prominence
  4. Failure of fusion of the lateral palatine shelf with the nasal septum
Show answer and explanation

Correct answer: C. Failure of fusion of the maxillary prominence with the medial nasal prominence

  • A. Neural crest cell migration issues contribute to various craniofacial conditions; the specific cleft lip defect is the fusion failure described in option A.
  • B. Failure of the two lateral palatine shelves to fuse causes cleft PALATE (posterior palate), not cleft lip.
  • C. Correct. Cleft lip results from failure of fusion of the maxillary prominence (paired) with the medial nasal prominence (unpaired, midline) during weeks 4–7 of embryogenesis. This leaves a cleft in the upper lip, which is more common on the left side and more common in males.
  • D. Failure of the lateral palatine shelf to fuse with the nasal septum causes cleft PALATE — not cleft lip.

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