the digestive system

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digestive physiology the digestive system lecture outline basic gi functions regulation of gi function phases of digestion absorption protective function of the gi tract basic gi functions primary function movement of nutrient molecules from the external environment to the internal environment done through the processes of: basic gi functions secondary functions mass balance ensuring daily fluid input and output are equal protection gi tract provides a huge external surface for pathogens to gain entrance into the internal environment lecture outline basic gi functions regulation of gi function phases of digestion absorption protective function of the gi tract regulation of gi function what is regulated? all aspects of the gi processes regulated by in general the signals are: neural hormonal paracrine specifically the controls and systems are: the long & short reflexes gi peptide reflexes the autonomous function of the enteric nervous system (ens) regulation of gi function long & short …

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ptide reflexes peptides released by the gi tract may act as hormones secreted into the blood act on accessory organs, other parts of the gi tract or the brain as paracrine signals secreted into the lumen or extracellular fluid lumenal signals bind to apical epithelial receptors ecf signals act in the immediate vicinity of secretion effect peptides alter secretion and motility alter behavior related to eating regulation of gi function gi peptide reflexes gastrin family secretin family peptide family secretin family regulation of gi function enteric nervous system allows for the autonomous behavior of the digestive system cns control is not required for digestive functioning commonalities between ens and cns intrinsic neurons – similar to interneurons of cns extrinsic neurons – composed of autonomic neurons neurotransmitters and neuropeptides nonadrenergic and noncholinergic receptors same as adrenergic and cholinergic in cns glial support cells – similar to astrocytes in cns diffusion barrier …

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ce food is in the mouth? secretion of saliva physical digestion via mastication chemical digestion via salivary amylase and lingual lipase (from von ebner’s glands) preparation for swallowing (deglutition reflex) bolus pushed against soft palate by tongue to trigger reflex ues (upper esophageal sphincter) relaxes, larynx elevates as epiglottis bends to cover trachea peristalsis and gravity moves bolus down esophagus to stomach phases of digestion gastric phase deglutition reflex (swallowing) moves food to the stomach to start the gastric phase 3.5 liters of content/day enters fundus controlled by long (vagal reflex) and short (distention & peptides/amino acids) reflexes phases of digestion gastric phase what does the stomach do? stores incoming food digests the food into chyme by action of pepsin and mechanical digestion (churning) protection acidic gastric environment mucous provides “self” protection phases of digestion gastric phase stores incoming food fundus exhibits receptive relaxation controls movement into the duodenum storage …

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yloric sphincter activity and lower stomach motility phases of digestion cephalic phase phases of digestion gastric phase protection acidic gastric environment mucous provides “self” protection phases of digestion integration of cephalic & gastric phases phases of digestion intestinal phase the final products of the cephalic and gastric phase is digestion of proteins formation of chyme controlled entry of chyme into the intestine starts the intestinal phase which contains loops that feed back to further control gastric emptying feed forward to promote digestion, secretion, motility and absorption of nutrients signals are hormonal & neural phases of digestion intestinal phase hormonal and neural aspects of the intestinal phase entrance of chyme into duodenum gets the enteric nervous system going, secreting: secretin slows gastric emptying & gastric acid production stimulates bicarbonate (hco3-) production from pancreas to buffer acidic chyme cholecystokinin (cck) secreted in response to lipids and slows gastric motility and gastric acid …

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stric phases phases of digestion intestinal phase the large intestines main processes are concentrating waste removal of water only about .1l of water lost daily through feces movement & defecation ileocecal valve controls chyme entrance into colon relaxes in sequence with intestinal peristalsis as well as when gastric emptying starts (gastrocolic reflex) cck, serotonin and gastrin are potential initiators of the gastrocolic reflex defecation reflex increases abdominal pressure, relaxes anal sphincters digestion and absorption digestion mainly through bacterial action which produces lactate and fatty acids which are absorbable by simple diffusion bacterial action also produces vitamin k by product of bacterial fermentation is gas (co2, methane & hs) lecture outline basic gi functions regulation of gi function phases of digestion absorption protective function of the gi tract absorption carbohydrate absorption absorption protein absorption absorption lipid digestion & absorption absorption absorbed nutrients and water are returned via the hepatic portal system …

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О "the digestive system"

digestive physiology the digestive system lecture outline basic gi functions regulation of gi function phases of digestion absorption protective function of the gi tract basic gi functions primary function movement of nutrient molecules from the external environment to the internal environment done through the processes of: basic gi functions secondary functions mass balance ensuring daily fluid input and output are equal protection gi tract provides a huge external surface for pathogens to gain entrance into the internal environment lecture outline basic gi functions regulation of gi function phases of digestion absorption protective function of the gi tract regulation of gi function what is regulated? all aspects of the gi processes regulated by in general the signals are: neural hormona...

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