Digestion II Motility Secretion Chapter 19 pages 610 633 Salivary Glands Fig 19 9 Salivary Glands Parotid amylase ptyalin 1 4 hexose linkages Submaxillary Sublingual mucin protein for lubrication Salivary Glands Acinus type glands Primary secretion by secretory cells and then modified by duct cells as saliva passes through on the way to the oral cavity Accessory Gland Structure Fig 19 8 Acinus Cells Fig 1 Fig 28 19 8 Primary Secretion K Na HCO3 Cl To Oral Cavity Saliva As saliva flows down duct Na and Cl decrease HCO3 and K increase also decreases As flow rates increase this exchange is less complete Salivary pH Saliva pH is basic vs plasma pH WHY i e for what purpose Excitatory Signal Molecules ACh from Parasympathetic NS onto muscarinic receptors VIP from enteric NS Increased blood flow in response to kininogen activation Kininogen Activation Glands release Kallikrein when activated Plasma globulin Results in peptide bradykinin Bradykinin local vasodilation 10X increase in BF Other Components of Saliva Muramidase cleave muramic acid in bacterial cell walls Lactoferrin binds Fe Epidermal growth factor stimulates mucosal cell growth IgA Lingual lipase small amounts ABO antigens secreters Salivary Secretion Cephalic Phase Thought or sensory input Gastric Phase Distention Secretagogues Vagal Vagal reflex Peristalsis Requires only enteric n s for short distances Enhanced by parasympathetic excitation duration velocity amplitude all increased Reflex relaxation ensures oral anal direction sphincter opening Stomach Figure 19 4 Stomach Mucosal Surface Folds are called Rugae gastricae Achalasia failure to open esophageal sphincter Sphincters Esophagus Esophageal Pyloric Cardia Pyloris Antrum Antrum Corpus Body Duodenum Fig 27 10 Gastric Glands Cardiac mucous producing columnar cells Pyloric mucous and G cells producing peptide hormone gastrin Oxyntic Oxyntic Glands Surface Epithelium insoluble mucous Neck Cells soluble mucous G cells gastrin Parietal or oxyntic Cells HCl Intrinsic Factor Chief Cells pepsinogen D cells enterogastrones Stomach Lumen Surface m ucous cell Gastric Pit Mucous neck cell Parietal Cell Oxyntic Gland Chief cell Gastric Acid Secretion Fig 19 22 Parietal Cell P L A S M A CO2 Cl HCO 3 H HCO3Cl Na K K Fig 19 22 H K Cl H K K Cl Fig 28 6 Histamine From enterochromafin like cells ECL cells in the gastric mucosa produce store release histamine activated by ACh gastrin secretagogues L U M E N PARIETAL CELL Histamine H2 receptor Fig 19 22 ATP cAMP K GASTRIC H ION PUMP H Gastrin ACh Ca Fig 28 6 Postprandial Alkaline Tide Treatment of Hyperacidity Atropine Cimetidine Antihistamine H2 antagonists Pepsin Pepsinogen pepsin in acidic conditions of stomach It is a family of endopeptidases pH optima 1 8 3 5 Activation of Pepsin Fig 19 14 Pepsin Activity moles min mg enzyme 1 0 3 0 5 0 Gastric pH Intrinsic Factor binds Vitamin B12 protects it from gastric and intestinal digestion absorbed as IF Vit B12 complex in ileum by receptor mediated endocytosis absence pernicious anemia Secretagogues caffeine and theophylline peptides spices Alcohol aspirin Table 19 2 Gastrointestinal Hormones Contol of G I Function Fig 19 21 GASTRIN Peptide hormoneFrom G cells Increases HCL pepsinogen secretion Increases gastric motility and emptying into duodenum Gastric Acid Secretion Cephalic Phase Fig 19 23a Thought of food smell chewing swallowing Vagus nerve to parietal cells ACh Vagus nerve ACh onto G cells thus causes gastrin release See TABLE 19 2 Gastric Phase Fi 19 23b Stomach distention peptides Local enteric reflexes vagovagal reflexes to Parietal cells ACh G cells release gastrin Gastric Acid Secretion Intestinal Phase Stimulus digested peptides peptides in duodenum distention G cells gastrin distention Intestinal endocrine cells release enterooxyntin Inhibition of Gastric Secretion Important for protection of duodenum Gastric pH 3 gastric D cells release somatostatin which inhibits gastrin release Acid in duodenum secretin CCK inhibits gastric secretion and motility Acid fats hyper osmotic solutions in the duodenum release of enterogastrones inhibit gastric motility and secretion Gastric Inhibitory Peptide GIP from duodenum inhibits parietal cell function Inhibitors of Gastric Secretion GIP CCK Secretin See Table 19 2 Ulcers Peptic Duodenal Role of Helicobacter pylori Vomit reflex Note sympathetic symptoms Fig 19 10 The Pancreas Fig 19 11a Liver Fig 19 11b Liver PANCREAS Sphincter of Oddi LIVER Gall Bladder PYLORIS DUODENUM Cholecystokinin CCK Secretin Both hormones produced in duodenum in response to chyme content Hormone receptors in pancreatic cells Pancreatic Secretions Hydrelatic HCO3 rich aqueous fluid neutralizes stomach HCl dilutes the chyme Ecbolic enzyme rich secretion Proteases endopeptidases Trypsinogen trypsin Chymotrypsinogen chymotrypsin Proelastase elastase Proteases exopeptidases Procarboxypeptidase carboxypeptidase Proaminopeptidase aminopeptidase amylase Lipases Ribonuclease Deoxyribonuclease Pancreatic Acinar Cell Secretin cAMP Bom besin ACh Ca ENZYMES CCK Substance P Protease Activation Pancreatic secretion contains trypsinogen and trypsin inhibitor Enterokinase in intestine activates trypsin Trypsin inhibitor is diluted by chyme Hormonal Regulation of Pancreatic Secretion Secretin peptide hormone pancreatic secretion rich in HCO3 Cholecystokinin CCK peptide hormone 33 amino acids pancreatic secretion rich in enzyme Pancreatic Secretion Cephalic Phase Sight taste smell of food Release of ACh gastrin in response to vagal stimulation Increased pancreatic flow especially ecbolic Gastric Phase Protein in chyme gastrin Gastric distention ACh from vagus Increased pancreatic secretion esp ecbolic Intestinal Phase Acid in chyme secretin hydrelatic secretion Long chain fatty acids amino acids and peptides in chyme CCK vagovagal reflex ecbolic secretion Bile from the Liver Bile Acids Primary from cholesterol by addition of OH and COOH Secondary formed in intestine by resident bacteria conjugated to taurine or glycine Bile Flow Released as CCK causes contraction of gall bladder and relxation of Sphincter of Oddi CCK 33 amino acid hormone released in response to fatty acids and lipids in chyme Gall Bladder Storage of Bile Gall Bladder stores bile and removes Na and water Thus bile may be concentrated as much as 20X Recirculation and reuse of bile salts and acids Bile salts and acids are reabsorbed from intestine ileum into portal blood From portal blood liver reabsorbs bile salts