1. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings The Gastric Phase  Storage  Stomach stores food and controls its passage into the small intestine  Digestion  Stomach  Chemical: Acid, enzymes, and signal molecules  Mechanical  Protection  Stomach acid destroys many bacteria and other pathogens. Stomach protects itself w/thick mucus

2. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-25 The Gastric Phase Activity of secretory cells of the gastric mucosa

3. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings The Gastric Phase Integration of cephalic and gastric phase secretion in the stomach Figure 21-26 Lumen of stomach Gastric mucosa Enteric plexus Chief cell Gastrin Somatostatin Amino acids or peptides Input via vagus nerve Enteric sensory neuron Enteric sensory neuron Enterochromaffin-like cell G cell D cell H+H+ Food Histamine Pepsin Pepsinogen Parietal cell KEY Stimulus Integrating center Receptor Efferent pathway Negative feedback pathway Food or cephalic reflexes initiate gastric secretion. Gastrin stimulates acid secretion by direct action on parietal cells or indirectly through histamine. Acid stimulates short reflex secretion of pepsinogen. Somatostatin release by H + is the negative feedback signal that modulates acid and pepsin release. 1 2 3 4 1 2 3 4 1 +

4. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-26, step 1 The Gastric Phase Lumen of stomach Gastric mucosa Enteric plexus Gastrin Amino acids or peptides Input via vagus nerve Enteric sensory neuron G cell Food KEY Stimulus Integrating center Receptor Efferent pathway Food or cephalic reflexes initiate gastric secretion. 1 1 1

5. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-26, steps 1–2 The Gastric Phase Lumen of stomach Gastric mucosa Enteric plexus Gastrin Amino acids or peptides Input via vagus nerve Enteric sensory neuron ECL cell G cell H+H+ Food Histamine Parietal cell KEY Stimulus Integrating center Receptor Efferent pathway Food or cephalic reflexes initiate gastric secretion. Gastrin stimulates acid secretion by direct action on parietal cells or indirectly through histamine. 1 2 1 2 1

6. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-26, steps 1–3 The Gastric Phase Lumen of stomach Gastric mucosa Enteric plexus Chief cell Gastrin Amino acids or peptides Input via vagus nerve Enteric sensory neuron Enteric sensory neuron ECL cell G cell H+H+ Food Histamine Pepsin Pepsinogen Parietal cell KEY Stimulus Integrating center Receptor Efferent pathway Food or cephalic reflexes initiate gastric secretion. Gastrin stimulates acid secretion by direct action on parietal cells or indirectly through histamine. Acid stimulates short reflex secretion of pepsinogen. 1 2 3 1 2 3 1

7. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-26, steps 1–4 The Gastric Phase Lumen of stomach Gastric mucosa Enteric plexus Chief cell Gastrin Somatostatin Amino acids or peptides Input via vagus nerve Enteric sensory neuron Enteric sensory neuron ECL cell G cell D cell H+H+ Food Histamine Pepsin Pepsinogen Parietal cell KEY Stimulus Integrating center Receptor Efferent pathway Negative feedback pathway Food or cephalic reflexes initiate gastric secretion. Gastrin stimulates acid secretion by direct action on parietal cells or indirectly through histamine. Acid stimulates short reflex secretion of pepsinogen. Somatostatin release by H + is the negative feedback signal that modulates acid and pepsin release. 1 2 3 4 1 2 3 4 1 +

8. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-27 The Gastric Phase The mucus-bicarbonate barrier of the gastric mucosa

9. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-28 The Intestinal Phase The effects of intestinal-phase events on gastric function

10. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings The Intestinal Phase  Bicarbonate neutralizes gastric acid  Goblet cells secrete mucus for protection and lubrication  Bile  Fat digestion  Digestive enzymes  Enteropeptidase

11. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-29 Activation of Pancreatic Zymogens

12. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-30 Hepatic Portal System Most fluid is absorbed in the small intestine

13. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings The Intestinal Phase  Most digestion occurs in small intestine  Large intestine concentrates waste for excretion  Motility in large intestine  Mass movement triggers defecation  Defecation reflex  Digestion and absorption in large intestine  Diarrhea can cause dehydration

14. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-31 Anatomy of the Large Intestine

15. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-31a Anatomy of the Large Intestine

16. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-31b Anatomy of the Large Intestine

17. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-31c Anatomy of the Large Intestine

18. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Immune Function  M cells sample the contents of the gut  Immune cells secrete cytokines  Cytokines trigger inflammatory response  Increase in Cl –, fluid, and mucus secretion  Vomiting is a protective reflex

19. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Summary  Function and processes  Digestion, absorption, motility, secretion, and GALT  Anatomy  Motility  Tonic and phasic contractions  Slow wave potentials, interstitial cells of Cajal, migrating motor complex, peristaltic contractions, and segmental contractions

20. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Summary  Secretion  Parietal cells, CFTR chloride channel, mucous cells, goblet cells, saliva, and bile salts  Regulation  Short reflexes, ENS, long reflexes, intrinsic neurons, gastrin family, secretin family, and other hormones

21. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Summary  Digestion and absorption  Amylase, disaccharidases, endopeptidases, exopeptidases, lipase, colipase, micelles, chylomicrons, and intrinsic factor  The cephalic phase  The gastric phase  Mucous cells, chief cells, D cells, ECL cells, and G cells

22. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Summary  The intestinal phase  Brush border, mass movement, and defecation reflex  Immune functions  M cells and vomiting