True about umbilical cord ?

Umbilical cordUmbilical cord develops from connecting stalk, which extends from the caudal end of the embryo to the chorion.Umbilical cord is covered by amniotic epithelium and contains a core of mesenchyme known as whaan's jelly.Contents of umbilical cord are : (i) Whaon's jelly, (ii) Two umbilical aeries, (iii) One (left) umbilical vein, (iv)Remnant of yolk sac, and (v) Remnant of allanto-enteric diveiculum.Initially 2 umbilical aeries and 2 umbilical veins develop in mesoderm, but right umbilical vein disappears. Left umbilical vein persists along with 2 umbilical aeries.At full term, the umbilical cord measures 1-2cm in diameter, and 50-55cm in length and generally attached to the center of fetal surface of placenta.