Question #256
The ductus venosus:
The ductus venosus connects the left umbilical vein to the inferior vena cava, thus re-directing oxygenated blood so that it bypasses the liver. After birth the connection with the placenta is lost and so the blood flow through the ductus venosus rapidly drops. This results in a functional closure. Structural closure occurs subsequently over the following 1-2 weeks (different research papers state different times of closure). The time of closure seems to vary depending on a range of different factors including prematurity, and the exact mechanism remains unknown.
The ligamentum venosum is the remnant of the ductus venosus.
The ligamentum teres is the remnant of the left umbilical vein.