Embryology USMLE Step 1 Practice Question
A 2-year-old girl with tetralogy of Fallot presents with cyanosis and dyspnea on exertion. Vital signs show BP 95/60 mmHg, HR 118/min, RR 28/min, SpO2 88% on room air. Echocardiography confirms right ventricular outflow tract obstruction and ventricular septal defect. Genetic testing reveals a 22q11 microdeletion. She denies palatal abnormalities or hypocalcemia. Which neural crest-derived embryologic structure is most likely responsible for her cardiac defect?
Answer choices
- ASixth pharyngeal arch mesenchyme
- BCardiac neural crest cells from the truncus arteriosusCorrect answer
- CMesodermal layer of the endocardial cushions
- DFirst pharyngeal arch cartilage
- EEndoderm of the third pharyngeal pouch
- FEctoderm of the pharyngeal floor
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