The fresh-water isopod Lirceus fontinalis has a straight tubular digestive tract which for convenience is divided into a foregut, an intestine, a rectum, and two pair of lateral caeca. The esophagus, cardiac, and pyloric chambers collectively form the foregut. The gastric armature, an elaboration of the chitinous intima, provides the triturating mechanism of the cardiac chamber. The intima of the pyloric chamber forms a pressing and straining apparatus. The intestine, possessing a dorsal longtitudinal typhlosole and intestinal sphincter, is joined anteriorly by the two pair of lateral hepatopancreatic caeca. The rectum is short and terminated by way of the anus. The foregut and rectum are histologically similar, their walls consisting of a chininous intima, a mucosa of columnar epithelium, continuous bands of circular muscle, and scattered strands of longitudinal muscle. Histologically, the intestine is cellular in nature and possesses a chitinous intima. The muscularis of the midgut forms a segmented checkerboard pattern of spaced inner circular bands and spaced outer longitudinal bands, the hepatopancreatic caeca are hollow blind tubes composed of two types of cells.
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