ABSTRACT
A1 D The abdominal wall forms during the fourth week of gestation from differential growth of the embryo causing infolding in the craniocaudal and mediolateral directions. The lateral abdominal folds of the embryo meet in the anterior midline and surround the yolk sac, eventually constricting the yolk sac into a yolk stalk that becomes the site of the umbilical cord. During the sixth week of gestation, rapid growth of the intestine causes herniation of the midgut into the umbilical cord. By week 10, the midgut returns to the abdomen and undergoes rotation and fixation.
