The embryology of foregut malformations

Developmental disorders in the period of the differentiation of the primitive foregut leads to atresia of the esophagus with tracheoesophageal fistula. Most authors think that this differentiation is caused by lateral foregut folds, which fuse in midline, thus forming the tracheoesophageal septum. In order to gain information about this period of development, we studied the foregut region of chick embryos by scanning electron microscopy (SEM) and light microscopy. In our study no signs of lateral folds or fusing foregut wall components, which were forming a tracheoesophageal septum, were found. Our study suggests that the development of the esophagus and trachea is the result of a simple reduction of the size of the primitive foregut. The consequence for the understanding of the embryology of the foregut malformations is discussed.