Profile view of a human embryo estimated at twenty or twenty-one days old. (Dorsal aorta labeled at center left.)
Each primitive aorta receives anteriorly a vein—the vitelline vein—from the yolk-sac, and is prolonged backward on the lateral aspect of the notochord under the name of the dorsal aorta. The paired dorsal aortae arise from aortic arches that in turn arise from the aortic sac.
The two dorsal aortae combine to become the descending aorta in later development.