After birth, the ductus arteriosus becomes which ligament?

• A. Ligamentum venosum
• B. Ligamentum arteriosum
• C. Ligamentum teres
• D. Falciform ligament

Answer: (B)

After birth, the ductus arteriosus closes as the newborn’s lungs take over gas exchange. The rise in oxygen tension and fall in prostaglandin levels cause the smooth muscle in the ductus arteriosus to constrict, stopping the abnormal right-to-left flow from the pulmonary artery to the aorta. Over time this functional closure becomes permanent, and the ductus arteriosus is transformed into a fibrous cord called the ligamentum arteriosum. This remnant runs from the proximal aorta to the proximal pulmonary artery and helps anchor the great vessels.

For context, the other ligaments are remnants of different fetal structures: the ligamentum venosum is the fibrous remnant of the ductus venosus in the liver; the ligamentum teres is the remnant of the umbilical vein; and the falciform ligament is a peritoneal fold that contains the ligamentum teres.