part of adult midgut region R3ab adult midgut region adult midgut region R3b 2014-06-05T17:29:32Z FBbt:00110899 Subregion at the middle zone of the adult midgut region R3. It is composed of copper cells (cuprophilic cells) interspersed with interstitial cells. The anterior region R3a is distinguishable from R3b by gene expression. region C of the adult middle midgut fly_anatomy.ontology