Changes

After emerging from the heart the Aortic artery divides in the Right and Left Dorsal branches. Each branch feeds into a set of arches which are unique to the embryo. Most higher vertebrates have have 6 paris of aortic arches. In the mammal the 5th pair do not form. These arches evolve to form some of the structures of the mammalian circulation. The fate of each arch varies.

After emerging from the heart the Aortic artery divides into the right and left Dorsal branches. Each branch feeds into a set of arches which are unique to the embryo. Most higher vertebrates have have 6 paris of aortic arches. In the mammal the 5th pair do not form. These arches evolve to form some of the structures of the mammalian circulation. The fate of each arch varies.

* Arches 1 and 2 degenerate completely.

* Arches 1 and 2 degenerate completely.

* The dorsal Aorta that runs between arches 3 and 4 degenerates on both the left and right sides.

* The dorsal Aorta that runs between arches 3 and 4 degenerates on both the left and right sides.

* The third arches form the internal carotid arteries

* The third arches form the internal carotid arteries

* The left fourth aortic arch forms part of the arch of the aorta.

* The left fourth aortic arch contributes to the arch of the aorta.

* The right fourth aortic arch forms the proximal segment of the right subclavian artery

* The right fourth aortic arch forms the proximal segment of the right subclavian artery

* The fifth aortic arches are never present in the mammal

* The fifth aortic arches are never present in the mammal

* The 6th aortic arch and the dorsal aorta on the right side degenerate.

* The proxiaml segment of the right sixth aortic arch forms part of the right pulmonary artery while the distal segment atrophies.

* The Left 6th arch forms the Ductus arteriosus

* The proxiaml segment of the left sixth arch forms part of the pulmonary artery while the distal segment forms the Ductus arteriosus.