Embryology of the anterior abdominal wall, bladder, and proximal urethra

During the first 3 weeks of development, the embryo is a plate of cells, the embryonic disk, whose ventral surface is a membrane called the somatopleure. The anterior abdominal wall is at first represented by the somatopleure of the overhanging head and tail folds. The somatopleure closes concentrically from the cranial, caudal, and lateral margins, centering on the future umbilical ring (Figure 49.1).