Embryologic Development and Defects · USMLE Step 1

A neonate with cyanosis worsens with feeding and improves with crying. Which embryologic defect most likely explains this?

  1. Choanal atresia
  2. Cleft palate
  3. Nasal septal deviation
  4. Laryngeal atresia
Show answer and explanation

Correct answer: Choanal atresia

Choanal atresia results from failure of the oronasal membrane to break down. Newborns are obligate nasal breathers, so feeding-related cyanosis is characteristic.

Difficulty: Medium Question 5 of 20

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