A neonate is found to have a persistent truncus arteriosus (failure of division of the truncus into the aorta and pulmonary trunk). Which embryological cell population is primarily responsible for this division, and its migration defect accounts for this malformation?

• A Lateral plate mesoderm cells migrating into the outflow tract
• B Epicardial cells (proepicardium) that form coronary arteries
• C Endocardial cushion cells that form the atrioventricular septum
• D Neural crest cells (cardiac neural crest) migrating from the postotic region into the truncus ✓

Explanation

Cardiac neural crest cells migrate from the postotic rhombomeres (rhombomeres 6-8) through pharyngeal arches 3, 4, and 6 into the truncus arteriosus and form the aorticopulmonary septum that divides the truncus into the ascending aorta (anteriorly) and the pulmonary trunk (posteriorly). Ablation or migration defect of cardiac neural crest causes persistent truncus arteriosus, transposition of great arteries, tetralogy of Fallot, and interrupted aortic arch (type B). Endocardial cushions form the AV valves and membranous interventricular septum — their defects cause AV septal defects, not outflow tract anomalies.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.