Median umbilical ligament
The median umbilical ligament is an unpaired ligamentous structure in human anatomy. It is covered by the median umbilical fold. Structure. It extends from the apex of the bladder to the umbilicus, on the deep surface of the anterior abdominal wall. It is a fibrous piece of tissue that represents the remnant of the fetal urachus. Lateral to this structure are the medial umbilical ligament and the lateral umbilical ligament. Development. The median umbilical ligament begins as the allantois in the embryonic period. It then becomes the urachus in the fetus. This later develops into the median  umbilical ligament at birth. It is also formed from the cloaca in utero. Function. The median umbilical ligament has no known function. Clinical significance. The median umbilical ligament may be used as a landmark for surgeons who are performing laparoscopy, such as laparoscopic inguinal hernia repair. Other than this, it has no function in a born human and may be cut or removed with impunity. It contains the urachus, which is the obliterated form of the allantois. The allantois forms a communication between the cloaca (terminal part of hindgut) and the amniotic sac during embryonic development. If the urachus fails  to close during fetal life, it can result in anatomical abnormalities such as a urachal cyst, urachal fistula, urachal diverticulum or urachal sinus. Society and culture. The median umbilical ligament was jokingly referred to as "Xander's ligament" in a YouTube video, and this name was subsequently used on Wikipedia for a short time. This term was later used in a paper published in Mayo Clinic Proceedings. The term has also appeared in a medical textbook of obstetrics and gynaecology.