It forms an umbilical ring of mesodermal condensation surrounding the coelomic portal, and is present in the 16 mm.
Cranially it lies ventral to the umbilical vein and on each side extends into the tissue of the lateral pillars of the cord bounding the coelom.
When the myotomic downgrowths reach the ventral aspect, their anterior portions (i.e. the sheaths of the recti muscles) become continuous with the tissue of the umbilical ring.
[2] When the umbilical ring has failed to close during the gestation (pregnancy) which results in a central defect in the lineal alba.
Umbilical hernias are smaller than one centimeter in size that it is present at birth but will only close in four to five years of life.