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Western University
Biology 2382B
Tom Haffie

Digestive System 4 Processes  Digestion o Ingesting the food  Absorption o Nutrient Absorption  Motility o Spontaneous movement  Secretion o Excreting waste Mouth  Beginning of digestion  No absorption of nutrient  Mechanical breakdown of food  Parotid gland o Secretes watery liquid + Amylase  Submandular Gland o Thicker liquid + Amylase  Sublingual Gland o Mucus + less Amylase Regulation of Saliva  Neuro Pathways  Positive Regulation o PSNS o SNS  PSNS o Major secretion  Initiates & regulates  SNS o Can’t initiate o Potentiates effects of PSNS Mastication  Chewing  Mechanical manipulation of food -> BOLUS  3 Stages o Voluntary o Pharyngeal o Esophageal Stomach  Bolus -> Chyme  Reservoir for food  2-3 L of gastric juices secreted everyday  4 Layers of Stomach o Mucosa  Epithelia  Slippery for food to move through o Sub mucosa  Collagen to make it stretchy o Smooth Muscle o Serosa  Covers the outside Mechanical Digestion  Pyloric Sphincter o Mixing and tossing of Chyme a little passed though it but most tossed back for more mixing and eventually little by little gets out Chemical Digestion  Inactivation of salivary Amylase and activation of Lingual Lipase  Production of HCL o To reduce pH  Very important for pepsin  Relies on pH for function  Pepsin o Protein digestion in stomach Functions of Acid in Stomach  Activates lingual lipase o Digestion of fatty acids  Activates pepsin o Pepsinogen + HCl -> Pepsin o Begins protein digestion  Inactivates salivary amylase  Kills microbes  Denatures proteins  Stimulates secretion of Hormones 4/28/2013 9:05:00 AM Pancreas  Endocrine and Exocrine Functions  Connected directly to Small Intestine Exocrine Secretion of Pancreas Produces Juices to send to Small Intestine for breakdown  Bicarbonate o Helps Neutralize pH of Chyme o HCl and Bicarbonate in Chyme  Pancreatic Amylase o Breaks down starch into maltose  Chymotripsinogen -> Chymotrypsin o Breakdown of proteins and polypeptides  Trypsinogen -> Trypsin o Enzyme o Breaks polypeptides into Peptides  Smaller amino acid chains  Procarboxypeptidase -> Carboxypeptidase o Helps with digestion  Pancreatic Lipase o Enzyme o Breakdown lipids Endocrine Secretion of Pancreas  Glucagon o When blood glucose gets too low releases glucagon in blood to bring it up o Alpha  Insulin o When blood glucose gets too high releases insulin in blood to bring it down o Beta  Somatostatin o Delta Function of Liver  Synthesis of bile salts o Need this to get cholesterol out of Chyme for the body  Excretion of Bilirubin o When red blood cells die o Heme is converted into bilirubin in liver o Excreted and gives stool the brown color  Also excreted in urine  Metabolism of Carbs, Lipids & Proteins  Processing of Drugs and Hormones Components of Bile  Bile Salts  Cholestrol  Bile Pigments o Bilirubin  Water and ions Schematic Diagram Gall Bladder  Store and concentrate bile produced by liver until needed Small Intestine (3 Regions)  Duodenum o Connected to stomach gets Chyme from stomach o Regulates digestion + Absorption  Jejunum o Most absorption of Nutrients o Amplified by # and Length of villi and microvilli  Ileum o Less absorption -> Low # in villi o Specific molecules absorbs Bile Layers of Small Intestine  Mucosa  Sub mucosa  Muscularis  Serosa Cells in the Intestinal Wall  Absorptive Cells o Epithelial cells with microvilli  Goblet Cells o Secrete Mucus  Intestinal Gland Cells o Secrete intestinal juices (Slightly Alkaline)  Paneth Cells o Secrete Lysozyme o Serve to constantly replenish epithelial cells that die and are lost from the villi.  S Cells o Secretes Secretin o To drop pH below 4 in small intestine  CCK Cell o Secrete Cholecystokinin o Digestion of fat and proteins  K Cells o Secrete glucose dependent insulinotrophic peptide (GIP) o Neutralize the pH drop from S Cells Microvilli (Brush borders) 
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