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The document discusses the hormones that regulate digestive activity in the gastrointestinal tract. It describes that gastrointestinal hormones are peptides secreted by enteroendocrine cells located along the mucosa. These hormones support the function of the organs that release them and enter the circulatory system rather than the GI lumen. Some hormones exhibit potentiation, where a combined action is greater than the individual effects. Specific hormones discussed include gastrin, cholecystokinin, secretin, gastric inhibitory polypeptide, and motilin.
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- 1. Hormone regulate digestive activityCharacteristics of GI hormoneGI hormones are peptidesIndividual enteroendocrine cells in the mucosa secrete GI hormone. GI hormone released from single cell located along the mucosa GI hormone support the function of the organ that releases themGI hormones enter the circulatory system, not the lumen of GI tract Some GI hormones exhibit potentiation. Potentiation occurs when a combined action of two hormones is greater than the sum of their individual effect
- 2. GI HormoneGastrinCholecystokinin (CCK)SecretinGastric inhibitory polypeptide (GIP)Motilin
- 3. GastrinG cells in the pyloric antrum of the stomach secrete gastrin.Gastrin stimulate hydrochloric acid (HCL) secretion in the stomach
- 4. CCKI cells in the duodenum and jejunum secret CCKCCK causes the gallbladder to contract moving bile to the small intestine It causes the exocrine pancreas to secret digestive enzymes into small intestineCCK stimulate growth of the exocrine pancreas and mucosa of gallbladder
- 5. SecretinS cells in the duodenum secret hormone secretinSecretin causes both the liver and the exocrine pancreas to secrete bicarbonate into small intestineSecretin inhibits gastric acid secretion
- 6. GIPCells in the duodenum and proximal jejunum secrete secret GIPIn the presence of glucose, GIP stimulate the secretion of insulin by endocrine pancreas
- 7. MotilinCells in the duodenum and jejunum secrete motilin about every 90 minutes during postabsorptive period Motilin moves the contents of the small intestine toward the terminal ileum
- 8. SecretionThe production and release of juices and hormones by the GI tract and its accessory glands
- 9. Fluid Secretion of GI TractIN Absorbed Eliminated800gm food ingested 750 gm 50 gm2 L fluid ingested1.5 L salivary 2 L gastric juice 8.85 L 0.15 L 1.5 L pancreatic fluid0.5 L bile1.5 L small intestine
- 10. Salivary GlandsSalivary glands produce salivaPaired parotid, submandibular and sublingual glands are called extrinsic glands because they are lie outside the oral cavityThere are smaller intrinsic salivary glands within the oral mucosa
- 11. Salivary GlandsSaliva delivered through ducts to the mouth its function:ProtectionSaliva dilute, buffers, cleanses and help prevent destruction of teethProduces lysozyme and IgA that capable of destroying certain bacteriaLubricationMucus eases passage of foodsDigestionAmylase digest carbohydrates
- 12. Nerves control of salivationIts mediated by the nervous systemBoth parasympathetic and sympathetic branch of ANS stimulate salivation
- 13. The parasympathetic is the primary controller of salivation Parasympathetic initiates and maintains salivation Stimulation of parasympathetic produces large amount of watery saliva containing enzyme Nerves control of salivation
- 14. Stimulation of salivationThought, smell and taste of food stimulate the salivary center in the medulla to increase parasympathetic activity and salivationAcidic substances and chewing food are powerful stimuli of salivation Inhibition of salivationFear, fatigue and sleep inhibits salivationNerves control of salivation
- 15. Esophagus SecretionMucus is the only secretion produced by the esophagus. Its function: Lubrication which facilitate passage of bolus along its length
- 16. Gastric SecretionThe gastric mucosal epithelium is made entirely of secretary cells includes exocrine, endocrine and paracrine cells Exocrine secrete products into the stomach lumen includes:Mucus: Secreted throughout the stomachPepsinogen: Secreted throughout the stomachHCL and intrinsic factor: Secreted from the same cell in the fundus and the body of the stomach
- 17. Enteroendocrine cells secrete gastrin and paracrine cells secrete histamine Gastrin Secreted in pyloric region of the stomach. Histamine secreted in the fundus and the body of the stomach. Gastric Secretion
- 18. Stomach SecretionGastric mucosa has gastric pits in the folds.Cells that line the folds deeper in the mucosa, are gastric glands.Insert fig. 18.7
- 19. Stomach Mucosa