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the superior area close to the choanae which is of ectodermal origin), the oesophagus, the stomach, and the initial part of the duodenum (the bulb); (2) middle part (the midget) communicating with the yolk sac and developing into the small intestine, and (3) the posterior part (hindguti), from which the large intestine develops.  Some histologists claim that the portion of the foregut up to the junction with the stomach has a cutaneous-type epithelium, which explains the sharp borderline where the epithelium of the oesophagus is continuous with that of the stomach which is derived from the entoderm.icd 10 training helps you to understand all these