- The pharyngeal arches grow out of the mesenchyme in the region of the head and neck and each contain a cranial nerve and artery.
- Between day 26 and 29, vasculogenesis and angiogenesis results in the formation of six pairs of aortic arches from the aortic sac. These arteries serve to connect the developing heart with the dorsal aorta.
- Endothelial precursor cells from surrounding mesoderm are and migration of neural crest cells are crucial to proper development of the aortic arches.
Fate of aortic arches
- 1st pair - forms between day 22 and 24, regresses as 2nd arch forms on day 26.
- 2nd pair - forms on day 26, later regresses.
- 5th pair - never forms or regresses early in development.
Origin of major blood vessels
- The common carotid arteries - arise from the 3rd AAA.
- The right and left internal carotid arteries - 3rd pair (proximal), cranial extensions of dorsal aorta (distal).
- The right and left internal carotid arteries - branch off common carotid arteries.
- The brachiocephalic artery - modification of area of aortic sac attached to 4th AAA; divides into right subclavian and right common carotid artery).
- The right subclavian artery (supplies right upper limb) - right 4th AAA, portion of right dorsal aorta, right 7th intersegmental artery.
- The left subclavian artery (supplies left upper arm) - left 7th intersegmental artery.
- The aortic arch and descending aorta - left 4th AAA, portion of dorsal aorta.
- The ductus arteriosus (patent during gestation, allows blood to shunt from pulmonary trunk to descending aorta, supplying developing fetus with oxygenated blood) - left 6th AAA.