Human Embryology and Teratology
Teaching text 7: Blood vessels and circulation 7: Aortic arches
The descent of the heart causes the formation of new aortic arches, which lead into the more caudally-located pharyngeal arches (pharyngeal arch arteries). At the same time, the already formed pharyngeal arch arteries partially degenerate. About 5 or 6 aortic arches develop in total but they are not all there simultaneously. The first two arches partially disappear before the last two develop.