Gross Anatomy USMLE Step 1 Practice Question
A 2-day-old male presents with micrognathia, malformed malleus and incus, and underdeveloped muscles of mastication causing feeding difficulty. Vital signs show HR 145 bpm, RR 48, and normal oxygen saturation on room air. Physical examination reveals small mandible with normal maxilla. Imaging confirms ossicular abnormalities. The child has no cleft palate. Which embryologic structure's maldevelopment most likely accounts for this constellation of findings?
Answer choices
- AFirst pharyngeal pouch
- BThird pharyngeal arch
- CSecond pharyngeal arch
- DFourth and sixth pharyngeal arches
- EFirst pharyngeal archCorrect answer
- FFirst pharyngeal cleft
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