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Bio& 242 Unit 1 / Lecture 4

Bio& 242 Unit 1 / Lecture 4. Hormonal control in the Digestive system: Gastric hormones. GASTRIN : Secretion: By enteroendocrine (G) cells in gastric pits of the mucosa. Stimulus: Stomach distention and acid pH of chyme causes Gastrin. Action: 1. increases HCl production in stomach

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Bio& 242 Unit 1 / Lecture 4

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  1. Bio& 242 Unit 1 / Lecture 4

  2. Hormonal control in the Digestive system: Gastric hormones GASTRIN: Secretion: By enteroendocrine (G) cells in gastric pits of the mucosa. Stimulus: Stomach distention and acid pH of chyme causes Gastrin. Action: • 1. increases HCl production in stomach • 2. increases gastric motility • 3. stimulates growth of gastric mucosa • 4. contract lower esophageal sphincter • 5. relaxes pyloric sphincter • 6. relaxes ileocecal sphincter

  3. Hormonal control in the Digestive system: Gastric hormones Somatostatin: Secretion: By enteroendocrine (D) cells in gastric pits of the mucosa in the pylorus. Stimulus: continuously released, overridden by Gastrin and nerves Action: • Inhibition of Gastrin production

  4. Hormonal control in the Digestive system: Small Intestinal hormones SECRETIN: Secretion: By Enteroendocrine (S) cells in the Crypts of Lieberkuhn of small intestine. Stimulus: Acid chyme in small intestine causes secretion of Secretin: Actions: • stimulate secretion of pancreatic juice and bile that is rich in bicarbonate ions. • inhibit production of HCl in stomach • promote growth and maintenance of the pancreas • enhance effects of Cholecystokinin (CCK) • Increases rate of bile secretion by hepatocytes

  5. Hormonal control in the Digestive system: small intestinal hormones CHOLECYSTOKININ (CCK): Secretion: Enteroendocrine (CCK) cells in the small intestine mucosa Crypts of Lieberkuhn Stimulus: Chyme rich in amino acids, triglycerides and fatty acids enter the small intestine. Actions: • increases secretion of pancreatic juice rich in digestive enzymes • opens the Sphincter of Oddi • contracts the gallbladder • Inhibits gastric secretion and motility • May reduce hunger

  6. Hormonal control in the Digestive system: small intestinal hormones Gastric Inhibitory Peptide (GIP): Secretion: Enteroendocrine cells in the small intestine mucosa Crypts of Lieberkuhn Stimulus: Chyme rich in triglycerides, fatty acids, and glucose enter the small intestine. Actions: • Stimulates release of insulin by beta cells • Inhibits gastric secretion and motility • Stimulates lipogenesis by adipose tissue • Stimulates glucose use by skeletal muscle cells

  7. Hormonal control in the Digestive system: small intestinal hormones Vasoactive Intestinal Peptide (VIP): Secretion: Enteroendocrine cells in the small intestine mucosa Crypts of Lieberkuhn Stimulus: Chyme entering the small intestine. Actions: • Stimulates buffer secretion • Inhibits gastric secretion • Dilates intestinal capillaries

  8. Hormonal control in the Digestive system Pancreas and Islets of Langerhans Endocrine cells make up 1% of the pancreas and are observed as Islets of Langerhans: 1. Alpha Cells: Secrete Glucagon (increases blood sugar) 2. Beta Cells: Secrete Insulin (decreases blood sugar) 3. Delta Cells: Secretes Somatostatin (inhibits secretion of both glucagon and insulin and prolongs rate of nutrient absorption / decrease depletion) 4. F-Cells: Secrete Pancreatic Polypeptide (inhibit secretion of digestive enzymes and inhibits contraction of the gallbladder)

  9. Enzymatic Digestion of Carbohydrates

  10. Enzymatic Digestion of Lipids

  11. Enzymatic Digestion of Proteins

  12. Enzymatic Digestion of Proteins

  13. Enzymatic Digestion of Proteins

  14. Enzymatic Digestion of nucleic Acids

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