Umbilical cord from and contains remnants of the yolk sac and allantois. It forms by the fifth week of development, replacing the yolk sac as the source of nutrients for the embryo. The cord is not directly connected to the mother's circulatory system, but instead joins the placenta, which transfers materials to and from the maternal blood without allowing direct mixing. The length of the umbilical cord is approximately equal to the crown-rump length of the fetus throughout pregnancy. The umbilical cord in a full term neonate is usually about 50 centimeters (20 in) long and about 2 centimeters (0.75 in) in
Medial umbilical ligament Medial umbilical ligament The medial umbilical ligament (or cord of umbilical artery) is a paired structure found in human anatomy. It is on the deep surface of the anterior abdominal wall, and is covered by the medial umbilical folds ("plicae umbilicales mediales"). It should not be confused with the median umbilical ligament, a different structure that represents the remnant of the embryonic urachus. It represents the remnant of the fetal umbilical arteries, which serves no purpose in humans after birth, except for the initial part that becomes the adult superior vesical artery. It may be used as a landmark for