A neonate has ductus arteriosus that failed to close. The ductus arteriosus is a remnant of which embryological structure?

• A Left fourth pharyngeal arch artery
• B Left third pharyngeal arch artery
• C Right sixth pharyngeal arch artery
• D Left sixth pharyngeal arch artery (distal part) ✓

Explanation

The ductus arteriosus is derived from the distal part of the left sixth pharyngeal arch artery. In fetal circulation, it connects the pulmonary trunk to the aortic arch, bypassing the lungs. The left fourth arch artery forms the arch of the aorta and the proximal left subclavian; the third arch forms the common and internal carotid arteries; the right sixth arch artery normally regresses (its distal part disappears — in the right, only the proximal part persists as part of the right pulmonary artery). The proximal part of the sixth arch on both sides forms the proximal pulmonary arteries.

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

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Written and medically reviewed by the StethoPrep medical team.