[clarification needed] It serves no function in adults but is the remnant of the ductus arteriosus formed within three weeks after birth.

[clarification needed] At the superior end, the ligamentum attaches to the aorta—at the final part of the aortic arch (the isthmus of aorta) or the first part of the descending aorta.

[2] On the other, inferior end, the ligamentum is attached to the top of the left pulmonary artery.

It is a vestige of the ductus arteriosus, a temporary fetal structure that shunts blood from the pulmonary arteries to the aorta.

This significantly reduces the volume of blood circulating through the lungs, which are inactive in the womb.