Six paired aortic arches, the so-called branchial arch arteries, develop between the ventral and dorsal aortae. These embryonic structures form during the development of the arterial system in intrauterine life. An aortic arch is a branch from the arterial aortic sac to the dorsal aorta. It travels in the centre of each pharyngeal arch, embedded in the mesenchyme. Initially, there are five pairs of arches, but these undergo structural changes and differentiation to form the definite vascular patterns for the head and neck, aorta, and pulmonary circulation.

During the fourth and fifth weeks of embryological development, when the pharyngeal arches form, the aortic sac gives rise to arteries – the aortic arches. The aortic sac is the endothelial lined dilation just distal to the truncus arteriosus; it is the primordial vascular channel from which the aortic arches arise. Each pharyngeal arch has its own cranial nerve and its own artery, hence we can conclude that the growth of the aortic and pharyngeal arches are very carefully related. The aortic arches terminate in the right and left dorsal aortae. The dorsal aortae remain paired in the region of the arches, however below this region they merge to form a single vessel (the descending/thoracic/abdominal aorta).

The pharyngeal arches and their vessels appear in a cephalo-caudal order, so they are not all present at the same time. As a new arch forms, the aortic sac contributes a branch to it. In the initial stage, there are pairs of aortic arches, which are numbered I, II, III, IV, and V. This system becomes altered in further development.

The truncus arteriosus divides into the ventral aorta and pulmonary trunk by the aortic-pulmonary septum. They represent the outflow channels of the heart. After this, the aortic sac then forms right and left horns. The right horn becomes the brachiocephalic artery, and the left becomes the proximal (ascending) part of the aortic arch.
The 1st Arch and 2nd Arch start to regress by approximately day 27, however portions of each persist as the maxillary artery, and the hyoid and stapedial arteries, respectively. By day 29 both these arches disappear entirely. Around the time regression of the 1st and 2nd arches, the 3rd is large and 4th, and 6th arches are forming. Soon the 3rd, 4th, and 6th arches all appear large. Because of the division of the truncus arteriosus, the 6th arches are now continuous with the pulmonary trunk, with the primitive pulmonary artery present as a major branch.
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