Figure 4.

(a) Diagram of the normal embryological origin of the RSCA from the seventh (VII) intersegmental artery with subsequent cranial migration, and dissolution (in black) of the R-PDA and right fourth (IV) aortic arch (R-arch). (b) Isolation of the RSCA occurs when there is dissolution (in black) of the right IV aortic arch but persistence of the right sixth (VI) arch from which the R-PDA and RPA take their origin. L-arch = Left aortic arch, LCCA = left common carotid artery, L-PDA = left ductus arteriosus, LSVC = left subclavian artery, LPA = left pulmonary artery, RCCA = right common carotid artery