This view through an endoscope shows the clear, bright, viscous, bubbly mucus which I mentioned here :
The thought of, sight of, smell of food causes certain parts of the stomach wall to secrete this copiously long before any food actually arrives post ingestion.
It's principal function is too provide protection for the stomach wall against digestion of itself by the powerful hydrochloric acid and enzymes also secreted.
Nobody knows what happens in Ivor Lewis patients where only a (variable in each operation) portion of the former stomach wall is used to re-construct a pseudo oesophagus and where the nerve supply to that tissue has been disrupted or removed.
Clearly in certain patients some normal function is retained given that one to two hours after every meal I cough up, in one gobbet, about a tablespoon of this substance. Curiously it is not in the least contaminated with any food residue.