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.

1. Hormone regulate digestive activity Characteristics of GI hormone GI hormones are peptides Individual 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 them GI 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 Hormone Gastrin Cholecystokinin (CCK) Secretin Gastric inhibitory polypeptide (GIP) Motilin

3. Gastrin G cells in the pyloric antrum of the stomach secrete gastrin. Gastrin stimulate hydrochloric acid (HCL) secretion in the stomach

4. CCK I cells in the duodenum and jejunum secret CCK CCK causes the gallbladder to contract moving bile to the small intestine It causes the exocrine pancreas to secret digestive enzymes into small intestine CCK stimulate growth of the exocrine pancreas and mucosa of gallbladder

5. Secretin S cells in the duodenum secret hormone secretin Secretin causes both the liver and the exocrine pancreas to secrete bicarbonate into small intestine Secretin inhibits gastric acid secretion

6. GIP Cells in the duodenum and proximal jejunum secrete secret GIP In the presence of glucose, GIP stimulate the secretion of insulin by endocrine pancreas

7. Motilin Cells 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 Tract IN Absorbed Eliminated 800gm food ingested 750 gm 50 gm 2 L fluid ingested 1.5 L salivary 2 L gastric juice 8.85 L 0.15 L 1.5 L pancreatic fluid 0.5 L bile 1.5 L small intestine

10. Salivary Glands Salivary glands produce saliva Paired parotid, submandibular and sublingual glands are called extrinsic glands because they are lie outside the oral cavity There are smaller intrinsic salivary glands within the oral mucosa

11. Salivary Glands Saliva delivered through ducts to the mouth its function: Protection Saliva dilute, buffers, cleanses and help prevent destruction of teeth Produces lysozyme and IgA that capable of destroying certain bacteria Lubrication Mucus eases passage of foods Digestion Amylase digest carbohydrates

12. Nerves control of salivation Its mediated by the nervous system Both 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 salivation Thought, smell and taste of food stimulate the salivary center in the medulla to increase parasympathetic activity and salivation Acidic substances and chewing food are powerful stimuli of salivation Inhibition of salivation Fear, fatigue and sleep inhibits salivation Nerves control of salivation

15. Esophagus Secretion Mucus is the only secretion produced by the esophagus. Its function: Lubrication which facilitate passage of bolus along its length

16. Gastric Secretion The 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 stomach Pepsinogen: Secreted throughout the stomach HCL 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 Secretion Gastric 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