The midgut,is primarily concerned with the production of enzymes and the absorption of the products of digestion. The hindgut conducts undigested food to the exterior via the anus, but also has other functions.In particular the rectum is involved in salt and water regulation The foregut Be lined with the intima().Surrounding the intima,which may be folded to enable the gut to stretch when filled,is a thin epidermis (肠壁细胞层)，small bundles of longitudinal muscle(纵肌)，a thick layer of circular muscle(环肌)，and a layer of connective tissue through run nerves and tracheae(气管)， Midgut 前中肠的分界限从外部看是胃盲囊(gastric caeca)从内部看是贲门 (cardiac valve) Be of endodermal(内胚层)origin.Have gastric caeca(胃盲囊)， ventriculus(胃)and peritrophic membrane(围食)in the midgut Prevent mechanical damage to the midgut cells and entry of microorganism into the body cavity. Be generally absent in fluid-feeding insects,such as,Hemiptera, adult Lepidoptera,and bloodsucking Diptera pylorus The pylorus is the first part of the hindgut and from it the Malpighian tubules(马氏管)often arise..In some insects it forms a valve between the midgut and hindgut.It regulate the movement of material from midgut to hindgut leum回肠 Be generally a narrow tube which serves to conduct undigested food to the rectum for final processing.In some insects,some absorption of ions or water may occur in this region. Rectum直肠 The rectum is often an enlarged sac (and is thin walled except for certain regions,the rectal pads(直肠)，which have a columnarThe midgut, is primarily concerned with the production of enzymes and the absorption of the products of digestion. The hindgut conducts undigested food to the exterior via the anus, but also has other functions. In particular the rectum is involved in salt and water regulation The foregut Be lined with the intima (内膜). Surrounding the intima, which may be folded to enable the gut to stretch when filled, is a thin epidermis （肠壁细胞层）, small bundles of longitudinal muscle（纵肌）, a thick layer of circular muscle（环肌）, and a layer of connective tissue through run nerves and tracheae（气管）. Midgut 前中肠的分界限从外部看是胃盲囊(gastric caeca)从内部看是贲门瓣 (cardiac valve) Be of endodermal（内胚层）origin. Have gastric caeca（胃盲囊）， ventriculus (胃) and peritrophic membrane（围食） in the midgut Prevent mechanical damage to the midgut cells and entry of microorganism into the body cavity. Be generally absent in fluid-feeding insects, such as, Hemiptera, adult Lepidoptera, and bloodsucking Diptera pylorus The pylorus is the first part of the hindgut and from it the Malpighian tubules（马氏管）often arise. In some insects it forms a valve between the midgut and hindgut. It regulate the movement of material from midgut to hindgut Ileum回肠 Be generally a narrow tube which serves to conduct undigested food to the rectum for final processing. In some insects, some absorption of ions or water may occur in this region. Rectum直肠 The rectum is often an enlarged sac（囊）and is thin walled except for certain regions, the rectal pads（直肠垫）, which have a columnar