The tracheoesophageal septum is formed from the tracheoesophageal folds which fuse in the midline to form a structure called tracheoesophageal septum. It divides the esophagus from the trachea. It divides the foregut tube into the laryngotracheal tube ventrally and esophagus dorsally. Developmental abnormalities can lead to a tracheoesophageal fistula. [ http://en.wikipedia.org/wiki/Tracheoesophageal_septum ]