BIOL 1080 Lecture Notes - Lecture 12: Esophagus, Pylorus, Gastrointestinal Tract
Document Summary
Gi tract represents a vast sa of the body that is exposed to external environment. Oral cavity (upper esophageal sphincter) esophagus (lower esoph. sphincter) stomach (pyloric sphincter) small intestine (ileocecal valve) colon (anal sphincter) rectum it sees not only our food, but potentially toxic substances & infectious agents. Mechanisms unique to this system to deal w this: Sa of a tennis court! sense & expel noxious substances vomit, diarrhea specialized populations of t-cells localized to intestinal mucosa. 28 ft. long (folded extensively in abdominal cavity) lg. luminal sa bw 200-400 sq. metres due to villi/microvilli highly variable transit time for an ingested meal w a marker (total of 30-40 hrs) 5-8 hrs in the stomach & sm intestine the rest in the colon houses resident gut microbiome (bacteria etc) & protect vs pathogenic microbes has its own intrinsic nervous system to control & coordinate all this functioning. Ns largely drives digestion) pepsin(ogen) & gastric lipase.
