part of adult posterior midgut adult midgut region adult midgut region R4 2014-06-05T17:29:32Z Adult midgut regions R4 and R5 correspond to the previously described posterior midgut (Buchon et al., 2013). Region of the adult midgut that forms a complex loop and that re-orients the gut towards the posterior part of the abdomen and ends ventrally. It can be subdivided into an anterior part containing an extremely folded epithelium (R4a) and two posterior regions composed of cells with short apical protrusions resulting in an enlarged lumen (R4b and R4c). FBbt:00110901 fly_anatomy.ontology