A newborn has a persistent truncus arteriosus. This defect arises primarily from failure of which embryological process?

• A Abnormal rightward looping of the primitive heart tube
• B Failure of endocardial cushion fusion producing an AV canal defect
• C Abnormal formation of the sinus venosus resulting in aberrant pulmonary vein drainage
• D Failure of neural crest cell migration into the conotruncal septum ✓

Explanation

Persistent truncus arteriosus results from failure of the aorticopulmonary (conotruncal) septum to divide the single truncus arteriosus into the aorta and pulmonary trunk. This septation is critically dependent on migration of cardiac neural crest cells from the rhombencephalon into the conotruncal ridges; ablation of these cells in experimental models reproducibly causes persistent truncus arteriosus. Conditions such as DiGeorge syndrome (22q11.2 deletion) impair neural crest migration and are associated with this defect. Endocardial cushion defects produce AV canal abnormalities, not conotruncal ones.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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