At S12, the umbilical ring encloses the following structures: 1) the omphalo-enteric duct together with its blood vessels (vasa omphalomesenterica), 2) the connecting stalk with the paired umbilical arteries and veins, and the allantois, and 3) the umbilical coelom (connection between the intra-embryonic (peritoneal cavity) and the extra-embryonic (chorionic cavity) coelom). After several processes of degeneration and transformation, only the two umbilical arteries and the left umbilical vein remain at birth.