Fetal-postnatal derivatives Fetal Structure Postnatal derivative Left umbilical vein Ligamentum teres (contained in falciform ligament) Right and left umbilical arteries Medial umbilical ligaments Ductus arteriosus Ligamentum arteriosum Ductus venosus Ligamentum venosum Foramen ovale Fossa ovale Allantois/urachus Median umbilical ligament Notochord Nucleus pulposus of intervertebral disk Aortic arch derivatives Arch Derivative 1st Part of maxillary artery branching from external carotid 2nd Stapedial artery and hyoid artery 3rd Common carotid arteries and proximal part of internal carotid arteries 4th On left, aortic arch On right, proximal part of right subclavian artery 5th Degenerates during development 6th Proximal part of pulmonary arteries Ductus arteriosus