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. Author manuscript; available in PMC: 2013 May 2.
Published in final edited form as: Semin Pediatr Surg. 2009 Feb;18(1):2–11. doi: 10.1053/j.sempedsurg.2008.10.002

Fig. 2. Theories on the development of oesophageal atresia and tracheo-oesophageal fistula.

Fig. 2

Schematic representations (sagittal sections) of the foregut illustrating the theories to explain the faulty organogenesis in oesophageal atresia (OA) and tracheo-oesophageal fistula (TOF). (a,b) In the first theory, the respiratory diverticulum (Rd) fails to elongate resulting in failure of the trachea to grow (tracheal agenesis) in contrast to the lung buds that develop normally. The overall growth and elongation of the foregut continues with the bronchial structures originating directly from the foregut. At a later stage, the foregut rostral to the bronchi assume tracheal (Tr) histological characteristics whereas the foregut distal to the bronchial origin connects to the stomach and is described as the fistula (Fi). The upper atretic oesophagus (Ao) results from rearrangement of the anterior foregut (arrow in b). (c,d) In the second theory, the process of tracheo-oesophageal separation becomes arrested (arrows in c and d). If the failure is only partial, a small length of oesophagus (Oe) does separate from the trachea, whereas total failure of separation yields an almost completely undivided tracheo-oesophagus. Following the arrest of separation, the undivided foregut assumes the histological characteristics of trachea whereas the initially separated oesophagus becomes the fistula that connects the trachea to the stomach. The upper atretic oesophagus forms, as in the first theory, by late rearrangement of the anterior foregut (dotted arrow in d). (e,f) In contrast to the first two theories, the third postulates that normal tracheo-oesophageal separation does take place. An insult to the embryo (possibly ischaemic) results in loss of part of the oesophagus (dotted lines in f) resulting in an atretic upper oesophageal pouch. The development of the fistula from the trachea (arrow in f) compensates for the oesophageal loss by reconnecting to the stomach. This theory suggests that the fistula is a structure of respiratory origin.