Question

A defect in which of the following aortic arches causes the defect shown in the image?

• A. 4th right
• B. 4th left
• C. 6th right
• D. 6th left

Answer 1

The Correct Option is D

The image reflects a defect associated with the development of the aortic arches in embryology. To determine the specific arch responsible for the defect, it's essential to understand the anatomy and the derivatives of these arches. During human development, several aortic arches form and then remodel into different structures:

• The 4th right aortic arch contributes to the right subclavian artery.
• The 4th left aortic arch contributes to the aortic arch (between the left common carotid and the left subclavian arteries).
• The 6th right aortic arch contributes to the right pulmonary artery.
• The 6th left aortic arch contributes to both the left pulmonary artery and the ductus arteriosus.

The defect in the image relates to an issue with the ductus arteriosus, which is derived from the 6th left aortic arch. The ductus arteriosus is crucial for fetal circulation as it allows blood to bypass the non-functioning fetal lungs. A failure in the closure or formation of this structure can lead to a patent ductus arteriosus, or other related defects. Thus, the answer is that a defect in the 6th left aortic arch causes the observed defect.