Which structure is in close relation to ligamentum arteriosum?

the ligamentum arteriOSum develops from the ductus arteriOSis in the fetus/embryo. the ductus arteriOSis is a bypass mechanism where blood is not transported to the lungs as they are not yet functional. after birth lungs are necessary (nolonger a placenta for oxygen) so ductus arteriOSum closes up and becomes the ligamentum arteriOSum