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The large intestine consists of the cecum, the colon, and the rectum, which share the same wall structure formed by, from inside to outside, a mucosa, a submucosa, a muscularis interna, a muscularis externa, and a serosa. The mucosa of the large intestine, comprising simple columnar epithelium and a lamina propria, forms deep cavities, the crypts of Lieberkühn, and, unlike the small intestine, lacks villi. The epithelium contains absorptive enterocytes with apical microvilli and many oval, mucous goblet cells. Deep in the crypts the epithelium contains enteroendocrine cells with granules in the cell portion facing the lamina propria. Large lymphoid aggregates, Peyer’s patches, occur in the submucosa throughout the intestines; M cells form part of the epithelium covering the Peyer’s patches.
In mice, the cecum has a large lumen and does not have an appendix. The mucosa of the cecum is thin, contains short crypts of Lieberkühn, and forms transverse folds.
The 4X and 10X micrographs of the cecum show its thin, folded mucosa with short crypts of Lieberkühn. The 20X micrograph depicts the Auerbach’s (myenteric) plexus, a network of neurons and nerve fibers located between the muscularis interna and the muscularis externa. The 40X micrograph illustrates the crypts of Lieberkühn in detail.
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