Neurodegenerative Diseases USMLE Step 1 Practice Question
A term newborn presents with abdominal distension, bilious vomiting, and failure to pass meconium within 48 hours. Vital signs show HR 145 bpm, RR 38/min, temp 37.2°C. Physical examination reveals no anal sphincter tone. Abdominal imaging demonstrates a transition zone in the distal colon with proximal bowel dilation. Rectal biopsy shows congenital absence of enteric ganglia in the aganglionic segment. Failure of migration of which embryologic cell population most likely caused this disorder?
Answer choices
- ANotochord
- BNeuroepithelial cells of the neural tube
- CParaxial mesoderm
- DSurface ectoderm
- ENeural crest cellsCorrect answer
- FEndoderm of the foregut
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations — plus adaptive practice that targets your weak areas — with a free MedBoardPRO account.