Embryologic Development and Defects · USMLE Step 1

A neonate presents with a persistent cervical sinus. This defect results from incomplete involution of which structure?

  1. Pharyngeal grooves
  2. Pharyngeal pouches
  3. Pharyngeal arches
  4. Branchial membranes
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Correct answer: Pharyngeal grooves

Persistent cervical sinus results from failure of the second pharyngeal arch to grow over the third and fourth pharyngeal grooves. It may form a branchial fistula or cyst.

Difficulty: Medium Question 16 of 20

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