GI tract FINAL Study Guide o Trick The Doctor s office o The GI tract is the waiting room for food o The blood is the actual examination room o The liver is the doctor and dictates what occurs in the examination Esophagus Stomach Small and Large I Mouth Rectum Gallbladder accessory to the GI Pancreas accessory to the GI Liver The Doctor o Accessory organs help with digestion of food o Mastication chewing breaks down food and increases Surface Area o Saliva Secreted from base of the tongue classic Salivary amylase Salivary lipase carbohydrates milk fat o Lysozymes o Esophagus Kill bacteria First defense against bacteria Muscular tube that connects the back of the mouth and the stomach Moves food through peristalsis Lower Esophageal Sphincter circular muscular valve Relaxes to let food into the stomach Constricts to keep food from moving back up into esophagus GERD Gastro Esophageal Reflux Disease Relaxation of lower esophageal sphincter Stomach acid comes in contact with esophagus Esophagus does not have protective lining against stomach acid Can lead to ulcers and increased risk of esophageal cancer Causes o Stomach Gastrin Spicy Foods Caffeine Fatty Foods Pregnancy Holds the food mechanical mixing and breaking down of food Gastric secretions Refer to Proteins page 19 o Release of HCL and pepsinogen o Pepsinogen denatures protein as well as lingual lipase which stops secretions activated by HCL HCL the digestion of fats and carbs in stomach o Also kills bacteria Emulsifying organs No absorption of macromolecules Absorption of alcohol and aspirin and minimal absorption of Vitamins and Minerals Mucus neutralizes acid Intrinsic factor o Pyloric sphincter protects stomach lining and contains bicarbonate which is necessary for absorption of B12 Circular muscular valve separating stomach from duodenum Regulates movement of food and acid from stomach to small I o CHYME ACID FOOD o Small Intestine 3 sections Duodenum most active and most important Main site of digestion and absorption Receives secretions from other digestive organs o Pancreas and Gall Bladder Lining of the small intestine is folded into finger like projections called villi Villi are lined with enterocytes that contain microvilli Brush Border Villi Enterocyte Microvilli o Digestion of nutrients usually completed on BB Enterocytes fully functional cells that line the villi o Produce enzymes have a nucleus Villar Tip Cells slough off Mid Villar Cells make digestive hormones CCK secretin GIP and enzymes for macronutrient digestion Crypt Cells Replication Digestion and absorption continues Absorption and enterohepatic circulation EHC of bile Jejunum Ileum o Large Intestine o Accessory organs Pancreas Smooth lining with no villi Absorption of water and electrolytes Temporary storage and concentration until defecation Microflora Breakdown of fiber Produce K and some B vitamins Makes enzymes and hormones Acini tissue o Secrete enzymes into GI tract Zymogens Pancreatic amylase CHO Pancreatic lipase Lipid Islet tissue o Secrete hormones into the blood Beta cells insulin Alpha glucagon Delta somatostatin o Not connected to the GI Liver Bile o Emulsifier for fats required for fat digestion o Made in hepatocytes from cholesterol o Stored in gallbladder o After digestion of fats bile is reabsorbed in ileum and sent back to the liver via EHC Metabolized drugs alcohol and other toxins Site of urea synthesis Plasma Transport Proteins o Albumin Major transport protein Maintains osmotic pressure Low albumin allows for fluid to leave bloodstream and pool in intercellular spaces edema transports iron o Transferrin o Lipoproteins fat soluble vitamins A D E K which carry cholesterol and transport The vascular system carries nutrients in blood to liver and then disperses it to the body EHC o Trick Liver has dibs on all nutrients in the body when we eat Lymph system carries exogenous lipids and they go into the bloodstream at the thoracic ducts Chylomicron Carbohydrates o Major source of energy fuel in the diet o Approximately of total caloric intake is in the form of CHO s o Glycogen is stored glucose liver and muscle o Different types of monosaccharide s Depends on number of carbons Pentose HMP shunt o Synthesized from hexose o Make ATP DNA and RNA Hexose glucose galactose fructose o Major source of Energy o Glucose Most abundant monosaccharide o Disaccharides condensation of 2 monosaccharides Glucose Glucose Maltose Glucose Galactose Lactose Glucose Fructose Sucrose o High fructose corn syrup A solution made form corn in a lab not natural 45 glucose and 55 fructose o Processed food o Gives food longer shelf life Sucrose and o Cane sugar and beet sugar Table Sugar o Oligosaccharides 3 10 monosaccharaides Found in beans peas whole bran and legumes such as kidney beans black eyed peas and black beans Unable to be enzymatically digested Travel to large intestine and fermented by bacteria causing flatulence o Polysaccharides Starch Storage form of CHO in plants Amylose o Linear molecule straight chain o Alpha 1 4 bonds of repeating glucose Amylopectin chain o Branched o Alpha 1 4 bonds straight chain o Alpha 1 6 branches Glycogen Storage form of carbs in animals Stored in liver and muscle o Liver increases amount of glycogen o Muscle increases the overall accumulation of glycogen Highly branched Fiber Energy from glycogenolysis Non digestible plant polysaccharides USDA Definitions o Dietary fiber naturally occurring intrinsic in plants and found intact o Functional fiber fiber added to food isolated manufactured or extracted from plant sources to add the benefit of fiber to foods deficient in fiber Insoluble fiber o NOT DIGESTIBLE o Does not dissolve in water o Decreases transit time time spent in gut o Increases fecal bulk o Ex Lignin celluloses and some hemicelluloses Soluble fiber Food Ex grape nuts o Dissolves in water o Increases transit time o Carries more bile Bile is 82 water o Ex Oatmeal pectin gums some hemicelluloses Soluble fiber NOT enzymatically digested is digested in large intestine by bacteria it is Humans lack the necessary micro flora to digest insoluble fibers Fiber is fermented in the large I producing hydrogen methane gas CO2 and Short chain fatty acids o Short Chain Fatty Acids SCFAs Stimulate water and sodium absorption into mucosa Provide colonocytes with energy Increase immune function via stimulation of immune cells and good bacteria production Without these we would get diarrhea Reduces atrophy of the gut Decreases
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