The aortic arch and its branches are formed during the fourth to sixth weeks of development from six pairs of embryological aortic arches (Bordes et al. 2021). The aortic sac develops as the first portion of the aorta, superior to the truncus arteriosus. The aortic sac then advances into two horns, right and left. The right horn gives rise to the brachiocephalic trunk, while the left horn forms the aortic arch proximal to the brachiocephalic trunk. The subclavian arteries are derived from the fourth aortic arch. As the aortic arches continue to develop asymmetrically, the origins of the right and left subclavian arteries differ (Rosen and Bordoni 2021). The right fourth aortic arch contributes to the right proximal subclavian artery, and the left gives rise to the medial segment of the arch of the aorta. The dorsal aorta gives rise to the intersegmental arteries. The cervical intersegmental arteries merge to form the vertebral arteries, except the left seventh intersegmental artery, which fuses with the aortic arch and exclusively forms the left subclavian artery. On the right side, the seventh intersegmental artery gives rise to the distal right subclavian artery (Rosen and Bordoni 2021). To summarize: the left subclavian artery is derived exclusively from the left seventh intersegmental artery, while the right subclavian artery is derived from the right horn of the aortic sac, the fourth aortic arch proximally and the right seventh intersegmental artery distally.