funiculus umbilicalis

In placental mammals, the umbilical cord (also called the birth cord or funiculus umbilicalis) is a conduit between the developing embryo or fetus and the placenta.

While the pulmonary artery and pulmonary veins are dilating, the umbilical artery and umbilical vein are severed due to the cutting of the umbilical cord, or the funiculus umbilicalis.