part of midgut interstitial cell adult midgut region R3ab enterocyte of middle adult midgut epithelium adult midgut interstitial cell 2014-06-05T17:29:32Z mEC FBbt:00110909 middle EC fly_anatomy.ontology Interstitial cell of the adult midgut. It is found in the anterior midgut subregions of region R3 (R3a and R3b, copper cell region), interspersed with copper cells. They have apically localized nuclei, short microvilli in the apical membrane and a broad apical profile. The interstitial cell arches over the apex of the copper cell, forming a narrow channel that connects the apical invagination of the copper cell to the gut lumen. The highly folded area of apicolateral contact between copper and interstitial cells contains smooth septate junctions.