Total of 6 aortic arches may develop from the distal truncus arteriosus or aortic sac.
Arches desappear at various times during development but terminate in the two dorsal aortae.
First 2 arches form maxillary, hyoid, and stapedial arteries. 2nd pair forms carotid arteries. 3rd pair leaves aortic sac and forms right and left horns, the right horn becomes the brachiocephalic trunk and the left horn along with the 4th aortic arch becomes the arch of the aorta. As ascending aorta leaves pericardium it divides into right and left aortic arch that join to form descending aorta. Left arch passes anteriorly and to the left of trachea and the right aortic arch passes to the right and posterior of esophagus.