GI TRACT I Oral Cavity A Mastication chewing breaks down food 1 Increases surface area B Saliva 1 Enzymes Salivary Amylase carbs Salivary Lipase fats milk fat 2 Lysozymes change pH and kill bacteria II Esophagus A Muscular tube connects back of mouth and stomach 1 Movement via peristalsis B Lower esophageal sphincter circular muscular valve 1 Relaxes food to stomach 2 Tightens to prevent backflow C GERD gastro esophageal reflux disease 1 Relaxation of lower esophageal sphincter 2 Stomach acid into esophagus 3 Possible Causes spicy food caffeine fatty food pregnancy 4 Esophagus damage over time ulcers and risk esophageal cancer III Stomach holding organ A Holds food B Mechanical mixing and food breakdown C Gastric secretions 1 Gastrin Release of HCl and Pepsinogen D Absorbs alcohol and aspirin 2 HCl Kills bacteria Denatures protein unfolds amino acid string Inactivates salivary amylase Converts pepsinogen pepsin 4 Mucus 3 Pepsinogen Inactive precursor to pepsin Protein digestion protects stomach lining contains bicarbonate 5 Intrinsic factor Necessary to B12 absorption IV Pyloric Sphincter A Circular valve between stomach and duodenum B Regulates food and acid movement small intestine C Chyme food acid V Small Intestine A 3 Sections 20ft total 1 Duodenum 1ft 2 Jejunum 3 Ileum B Lining 1 Folded into Villi 2 Villi covered with microvilli brush border 3 Digestion usually completed on brush border Microvilli brush cover enterocyte Enterocytes make up villi Villi are the folds 4 Enterocytes cells that line villi a Villar tip cells do most absorption b Mid villar cells c Crypt cells cell replication secrete digestive enzymes and hormones VI Large Intestine C Jejunum D Ileum 1 Digestion and absorption continue 1 Absorption 2 Enteropathic circulation of bile Remaining bile recycles back to liver A Smooth lining colonosites NO villi B Water and electrolyte absorption C Intestinal microflora 1 Bacterial breakdown of fiber 2 Produces vit K and some vitB D Temp storage and concentration until defecation VII Accessory Organs A Pancreas 1 Acini tissue secretes enzymes GI tract a Zymogens inactive enzymes b pancreatic amylase and lipase 2 Islet tissue a secrete hormones blood Beta insulin Alpha glucagon Delta Somatostatin B Liver 1 Makes bile a Emulsifies fat required for fat digestion b Bile Made in hepatocytes from cholesterol stored in gallbladder 2 Metabolizes drugs alcohol and toxins 3 Site of urea synthesis 4 Makes Plasma proteins a Albumin Major transport protein maintains osmotic pressure low albumin fluid leaves blood pool in intercellular spaces edema b Transferrin transports iron c Lipoproteins 5 types Chylomicron VLDL IDL LDL HDL VIII Circulation of Nutrients A Vascular System 1 Nutrients in blood liver body 2 Enterohepatic Circulation a Carbs and Proteins blood B Lymph System 1 Exogenous lipid transport 2 Lipids lymph body CARBOHYDRATES Major source of energy fuel in the average diet Approximately of total caloric intake in form of Polysaccharides starches and dextrins Simple Sugars sucrose lactose fructose I Chemical Structure A Simple 1 CH2O 2 Glyceraldehyde B Complex 1 Glucagon II Monosaccharides A Types based on carbon 3 Triose 4 Tetrose 5 Pentose 6 Hexose 7 Heptose 1 Glucose a Made from hexoses b Ribose ATP DNA RNA a Major source of energy source b Glucose fructose galactose B Dietary Monosaccharides Simple Carbs a Most abundant monosaccharide b C6H12O6 2 Fructose Galactose III Disaccharides B Types A Formed from condensation of 2 monosaccharides 1 Glucose glu maltose found in milkshakes and alcohol 2 Glu fructose Sucrose table sugar 3 Glu galactose lactose dairy products C High Fructose Corn Syrup HFCS 1 50 glucose 50 fructose sucrose a Cane and beet sugar processed sugar 2 45 glu 55 fru HFCS b Solution made from corn in processed foods IV Oligosaccharides A 3 10 monosaccharide string B Different bonds different digestion 1 Raffinose gal glu fruc 2 Stachyose gal gal gluc fruc V Polysaccharides A Starch 3 Found in beans peas and whole bran 4 Unable to be enzymatically digested Fermented by gut bacteria 1 Storage form of CHO in plants 2 Types a Amylose Glucose linked by a 1 4 bonds b Amylopectin Branched chain polymer a 1 4 chains and a 1 6 branches B Glycogen identical to amylopectin 1 Storage form of CHO in animals a Liver and Muscles 2 Highly branched 3 Energy Source a Glycogenolysis breakdown of glycogen C Fiber 1 Non digestible plant polysaccharides 2 Defined USDA a Dietary fiber found intact in plants b Functional fiber Has been isolated extracted or manufactured for beneficial effects 3 Types a Insoluble Doesn t dissolve in water Decreases transit time Ex lignans celluloses some hemicelluloses b Soluble Dissolves in water Increases transit time Ex pectin gums some hemicelluloses 4 Fermented by bacteria in colon a Hydrogen CO2 methane gas short chain fatty acids Short chain fatty acids Acetic Acid Butyric Acid Propionic Acid Functions of short chain fatty acids stimulate water and sodium absorption into mucosa provide colonocytes with energy enhanced immune function stimulates immune cells and good bacteria production Reduces atrophy of gut Reduced cholesterol by reducing pH reducing reabsorption Inhibits cholesterol synthesis in liver 5 Excreted as fecal matter carries bile with it 6 Sources Soluble fiber carries more bile than insoluble Fruits veggies and whole grain DRI 19 50 yrs 51yrs Men 38g 30g Women 25g 21g DIGESTION OF CARBOHYDRATES I Begins in mouth A Salivary glands produce salivary amylase 1 Digestion of a1 4 bonds amylose 2 Doesn t break down a1 6 bonds in amylopectin B Amylose Digestion C Branched starches 1 Not broken down D Action of salivary amylase is incomplete II Stomach A HCl inactivates salivary amylase 1 HCl denatures protein amylase is a protein Allergy is always to protein Lactose Intolerance inability to make lactase enzyme III Small Intestine A Pancreatic Secretions 1 bicarbonate neutralizes chime 2 Pancreatic amylase B Brush Border Enzymes 1 Sucrase breaks down sucrose glu fru 2 Lactase lactose glu gal 3 Maltase maltose glu glu CARB ABSORPTION AND TRANSPORT I Location A Small Intestine II Mechanisms for Transport A Passive Diffusion 1 No energy required 2 Limited by concentration gradient 3 Not usually seen w carbs 4 Small molecules and solutes B Facilitated Diffusion 1 Needs carrier protein a Integral membrane protein b Functions as a transporter 2 Rate determined by a Concentration gradient b Amount of carrier available c Rapidity of solute
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