part of peritrophic membrane FBbt:00003142 peritrophic matrix Non-cellular matrix composed of chitin and glycoprotein secreted into the lumen of the proventriculus (cardia), between the outer and intermediate layers by a group of cells in the anterior proventriculus. It covers the luminal side of the midgut posterior to the proventriculus, separating the midgut epithelial cells from the gut contents. It can be divided into 4 distinct layers in the proventriculus and 2 layers in the midgut. fly_anatomy.ontology midgut proventriculus acellular anatomical structure