An experimental study was conducted to determine the end-results of two different defects on the anterior abdominal wall: an abdominal wall defect (AWD) versus an umbilical cord defect (UCD) using chick embryos. The AWD was created by leaving an intact skin bridge between the defect and the umbilical cord in group 1; the UCD was created on the umbilical cord near the junction of the skin in group 2. At the end of incubation, the intestines appeared hemorrhagic in the AWD group, but not in the UCD group. During microscopic examination, hemorrhagic areas were observed in the bowel wall and mucosal villi in the AWD group but not in the UCD group. The end-result of the defect causing the physiological umbilical hernia resulted in bowel damage resembling the classic picture of gastroschisis (GS). We conclude that the site of the defect in GS is not the abdominal wall itself, but the physiological umbilical hernia.