The digestive-tract region containing specialized absorptive and secretory epithelium. Architecture differs between intestinal regions and species.
The intestinal lumen is the internal space through which gut contents pass. It is separated from underlying tissues and circulation by the intestinal epithelium. Material within the lumen has therefore entered the digestive tract without necessarily being absorbed into the body.
The rectum is the terminal large-intestinal region before the anal canal. Its storage and sensory properties contribute to controlled defecation. Distension, muscular activity and outlet coordination are different components of the resulting behavior.
The muscularis mucosae is a thin smooth-muscle layer associated with the gastrointestinal mucosa. It supports local movements of the mucosal region. It is distinct from the larger outer muscle layers generating much of whole-segment mixing and propulsion.
The lamina propria is the connective-tissue layer beneath the epithelium of a mucosa. It contains supporting cells, vessels and immune components. Its position links epithelial exchange with the deeper tissue environment while remaining distinct from the lumen.
A Peyer's patch is an organized lymphoid aggregation in the intestinal wall, particularly prominent in the ileum. It supports sampling and immune responses associated with gut contents. Its local position distinguishes it from a draining mesenteric lymph node.
Intestinal obstruction is impairment of onward passage through the intestine. Mechanical blockage and failure of coordinated propulsion are different routes to impaired transit. Distension and upstream accumulation describe consequences, not a unique cause.
The colon is the main elongated portion of the large intestine between the cecal region and rectum. Its segments support water and electrolyte handling, microbial processing and movement of contents. Anatomical position and transit behavior vary along its length.
Bowel is a common anatomical term for the intestine. Context should specify small or large bowel when their different functions matter. The broad word does not identify one single segment or uniform mucosal structure.
A lysosome-related organelle of the Caenorhabditis elegans intestine. Loss of granule formation can alter a gut-marker assay without eliminating the intestinal founder lineage.
The small intestine is the gut region between stomach and large intestine, divided into duodenum, jejunum and ileum. It performs extensive digestion and absorption. Surface organization and segment-specific transport link its anatomy to the processing of different nutrients.[ref]
The ileum is the distal part of the small intestine before entry into the large intestine. Its specialized transport includes recovery of bile-associated material and absorption of vitamin B12 under the appropriate carrier conditions. It also contains prominent gut-associated lymphoid structures.
The duodenum is the first small-intestinal segment after the stomach. Pancreatic and biliary secretions enter its region to support digestion and modification of gastric contents. Its anatomy connects digestive secretions from accessory organs with material arriving through the pylorus.
An epithelial invagination housing proliferative populations in the adult mammalian intestinal lining. Crypt structure, supporting cells and developmental timing vary with region and species.
A projection of the intestinal lining that increases exposed absorptive surface. Mammalian small-intestinal villi must be distinguished from microscopic microvilli on individual epithelial cells and from the normally non-villous colon.
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