GI-tract, what does it look like in there?

So, another question...

"Account for, in a systematic and comparative way, the tissues composition and build in the digestive systems different parts (from the stomach downward). Also describe the function of the parts of the immunsystem that are localized to the digestive system." 

Phew... I kinda choked on that question. But anyway once you break it down it is not so scary anymore. Here is a weird mind map on it.

The epithelium is simple columnar all the way from the stomach down to the anal canal.

Structure of the epithelium in the GI-tract