The Gastro Intestinal Tract Oral Cavity Esophagus Mastication chewing breaks down food increases surface area Saliva Enzymes Lysozymes Muscular tube connects the back of the mouth and stomach Movement of food via peristalsis Lower esophageal sphincter circular muscular valve Relaxes to let food into stomach GERD gastro esophageal reflux disease Relaxation of lower esophageal sphincter Stomach acid comes in contact with esophagus Possible causes 1 Spicy foods 2 Caffeine 3 Fatty foods 4 Pregnancy Stomach Holds food Mechanical mixing and breaking down of food Gastric secretions Gastrin 1 Release of HCL and pepsinogen Hydrochloric acid HCL 1 Kills bacteria 2 Denatures proteins 3 Inactivates lingual lipase Pepsinogen 1 Inactive precursor to pepsin Mucus 1 Protects stomach lining 2 Contains bicarbonate Intrinsic factor 1 Necessary for absorption of B12 Pyloric Sphincter Circular muscular valve separating stomach from duodenum Regulates movement of food and acid from stomach to small intestine Chyme acid food Small Intestine Three sections Jejunum Ileum Duodenum 1 ft 20 ft total Gastric bypass bypasses duodenum which is the main site of absorption digestion Duodenum receives secretions from gall bladder and pancreas Folded into finger like projections called villi Villi are covered with microvilli Lining Micro villi brush border Digestion of nutrients usually completed on brush border Enterocytes cells that line the villi 1 Villar tip cells the most absorption come off and are secreted as waste 2 Mid villar cells move up to the top of villi as tip cells are shed Secrete digestive enzymes and hormones CCK and secretin 3 Crypt cells responsible for cell replication Digestion and absorption continues Jejunum Ileum Absorption Enterohepatic circulation of bile bile is recycled by being absorbed in the ileum and then is sent back to the liver bile emulsifies fats all the way through the small intestine Large Intestine Smooth lining no villi Water and electrolyte absorption Intestinal microflora Bacterial breakdown of fiber Production of vitamin K and B Temporary storage and concentration until defecation Accessory Organs Pancreas Acini secrete enzymes into GI tract Zymogens inactive enzymes not digesting yet Pancreatic amylase and lipase Islet tissue Secrete hormones into blood 1 beta insulin 2 alpha glucagon 3 delta somatostatin not connected to GI Liver Makes bile 1 Emulsifier for fats required for fat digestion 2 Bile made in hepatocytes from cholesterol stored in gall bladder after digestion of fat bile reabsorbed in ileum enterohepatic circulation Metabolizes drugs alcohol and other toxins Makes plasma proteins Site of urea synthesis 1 Albumin major transport protein maintains osmotic pressure low albumin allows for fluid to leave blood stream and pool in intercellular spaces edema 2 Transferrin transports iron 3 Lipoproteins 5 types chylomicron VLDL IDL LDL HDL Carries various lipid cholesterol components to tissues Circulation of nutrients Vascular system Lymph system Carbohydrates Carries nutrients in blood to liver and then disperses it to body enterohepatic circulation everything passes through the liver first then to the rest of the body bloodstream Exogenous lipid transport Lipids lacteal takes them to the thoracic region not to the liver first Major source of energy fuel in the average diet Approximately of total caloric intake in the form of 1 Polysaccharides starches and dextrins 2 Simple sugars sucrose lactose and fructose Chemical structures Simple glyceraldehyde Complex glycogen Monosaccharides Types 1 3 triose 2 4 tetrose 3 5 pentose 4 6 hexose 5 7 heptose Hexose 1 Major source of energy 2 Glucose fructose and glactose Pentose Made from hexoses Ribose 1 ATP 2 DNA RNA Dietary monosaccharides Glucose most abundant monosaccharide blood sugar Fructose Galactose Disaccharides Formed from condensation of 2 monosaccharides Types Glucose glucose maltose dehydration rxn making water alcohol Glucose fructose sucrose table sugar Glucose galactose lactose dairy High fructose corn syrup 50 glucose 50 fructose 1 Cane sugar and beet sugar 2 Table sugar processed food 45 glucose 55 fructose HFCS 1 Solution made from corn 2 Processed foods Oligosaccharides 3 10 monosaccharides Raffinose gal glu fruc Stachyose gal gal gluc fruc Found in beans peas and whole bran Unable to be enzymatically digested but bacteria in get can ferment them differ in how they are held together Polysaccharides Starch Glycogen Storage form of CHO in plants Types 1 Amylose glucose linked by 1 4 bonds linear molecule 2 Amylopectin glucose linked by 1 4 bonds linear and 1 6 branches branches chain polymer Storage form of CHO in animals 1 Liver 2 Muscle Highly branched Energy source Glycogenolysis Non digestible Defined by USDA Fiber 1 Dietary fiber found intact and intrinsic in plants 2 Functional fiber has been isolated extracted manufactured and have beneficial effects Types 1 Insoluble does not dissolve in water decreases transit time increases fecal bulk ex lignans celluloses some hemicelluloses 2 Soluble dissolves in water increases transit time ex pectins gums some hemicelluloses Fermented by bacteria in colon 1 Hydrogen methane gas CO2 short chain fatty acids short chain fatty acids Acetic acid Butyric acid and Propionic acid Functions of short chain Fas a Stimulate water and sodium absorption into mucosa b Provide colonocytes with energy c Enhanced immune function d Reduces atrophy of gut preventing bacteria from entering blood stream and causes sepsus e Decreases cholesterol by 1 Decreasing pH of gut decreased reabsorption of bile and 2 May inhibit cholesterol synthesis in liver Excreted as fecal matter carries bile with it soluble fiber carries more bile than insoluble Sources Fruits vegetables and whole grains Digestion of Carbohydrates Begins in mouth Salivary glands produce salivary amylase Digests 1 4 bonds Does not break down 1 6 bonds Amylose digestion Branched starches Action of salivary amylase is incomplete 1 6 bonds time spent in mouth Stomach Small Intestine HCL inactivates salivary amylase and denatures proteins Pancreatic secretions Bicarbonate Pancreatic amylase Brush border enzymes Sucrase sucrose glucose fructose Lactase lactose glucose galactose Maltase maltose glucose glucose Absorption and Transportation of carbs Location Small intestine Mechanisms of transport Passive diffusion Facilitated diffusion Active transport Passive diffusion of solute through membrane No energy required Limited
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