A child is born with a defect where the aorta arises from the right ventricle and the pulmonary artery from the left ventricle (transposition of great arteries, D-TGA). This results from a defect in which embryological process?
- A Failure of the aorticopulmonary septum to spiral (conotruncal rotation defect) ✓
- B Failure of the primum atrial septum to fuse with the endocardial cushions
- C Incomplete muscular ventricular septal formation
- D Defective neural crest cell migration into the conus cordis
Explanation
In normal development, the aorticopulmonary (truncoconal) septum forms as two opposing ridges in the truncus arteriosus and conus cordis that spiral around each other (180°) before fusing, creating the aorta (posteriorly) and pulmonary trunk (anteriorly) in a helical arrangement. In D-TGA, this spiralling fails — the septum runs straight, so the aorta ends up anterior and rightward (from the morphological right ventricle) and the pulmonary trunk posterior and leftward (from the morphological left ventricle). Neural crest cells are required for this process, and defects in their migration can cause conotruncal anomalies, but the primary anatomical defect is non-spiralling. ASD primum involves endocardial cushion fusion failure.
Reference: BD Chaurasia's Human Anatomy, 8th ed.
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Written and medically reviewed by the StethoPrep medical team.