Persistent truncus arteriosus results from failure of which embryological process, and which mesenchymal structures are responsible for partitioning the primitive outflow tract?

• A Failure of the aorticopulmonary (truncal) septum, derived from neural crest cells migrating into the truncal cushions, to divide the truncus arteriosus into aorta and pulmonary trunk ✓
• B Failure of the muscular interventricular septum to fuse with the endocardial cushions
• C Failure of the septum primum to close the ostium secundum, resulting in persistent right-to-left shunting
• D Failure of the sinus venosus to be incorporated into the right atrium

Explanation

Partitioning of the truncus arteriosus into the aorta and pulmonary trunk is accomplished by the aorticopulmonary septum, which is formed by neural crest (ectomesenchymal) cells migrating from the rhombomeres into the truncal and conal cushions. These cushions grow and fuse in a spiral orientation, creating the spiraling relationship between aorta and pulmonary trunk. Neural crest cell migration defects (as in DiGeorge syndrome with 22q11 deletion) cause persistent truncus arteriosus, tetralogy of Fallot, and transposition of great arteries. Endocardial cushions form the AV canal division and membranous IV septum.

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

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Written and medically reviewed by the StethoPrep medical team.