Embryology, Great Vessel

The great vessels are a part of the vascular system that first appears in the mid-third week of development from mesoderm/ectoderm-derived angiogenic cells. The arteries arise from the combination of the ectoderm (cells from the neural crests) and the mesoderm (pharyngeal mesoderm). The first arteries that develop are the right and left primitive aortae, which are a continuation of endocardial cardiac tubes. These primitive aortae curve posteriorly in the first pharyngeal arch, around the anterior part of foregut and then continue posteriorly as two dorsal aortae. These two aortae also fuse cranially close to the heart, forming the aortic sac. The aortic sac continues caudally as truncus arteriosus and lies ventral to the pharynx. The two dorsal aortae lie dorsal to the primitive gut and pass caudally and fuse at the distal end to form a common aorta while the cranial part remains separate.