Term
| what is the GI responsible for? |
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Definition
| digestion, absorption, and elimination of nutrients |
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Term
| who discovered HCl in the stomach? |
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Definition
| william beaumont - found it in the guy with the hole in his stomach |
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Term
| what are the three phases of digestion? |
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Definition
| the cephalic, gastric, and intestinal phase |
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Term
| what does the cephalic phase consist of? |
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Definition
| the hypothalamus triggers hunger by integrating signals from nerve cells throughout the body, as well as from messages carried by hormones |
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Term
| what two major roles does peristalsis play? |
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Definition
| propulsion and mixing of the food through the GI tract |
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Term
| what are the 3 digestive enzymes in the mouth? what is the net effect? |
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Definition
| *alpha amylase which hydrolyzes alpha 1,4 linkages, *lingual lipase which hydrolyzes short and medium chain FAs, and *carbonic anhydrase which produces bicarb (neutralizes salivary pH). the net effect of the enzymes is breakdown of the the carbs into shorter saccharides and lipids into shorter FAs |
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Term
| is there any protein digestion in the mouth? |
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Definition
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Term
| what is the main purpose of the esophagus? why is acid particularly harmful to it? |
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Definition
| the main purpose of the esophagus is carrying food via peristalsis. the esophagus is not mucus coated and therefore if acid backs up into it, damage will occur |
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Term
| what starts the digestion of protein? |
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Definition
| the formation of pepsin from pepsinogen in the stomach (HCl activated) |
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Term
| are carbs digested in the stomach? |
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Definition
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Term
| are short and medium chain FAs digested in the stomach? |
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Definition
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Term
| what are the main functions of the stomach in digestion? |
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Definition
| the stomach performs a reservoir function (short term food storage ~4 hrs), churns chyme, and protein and lipid hydrolysis are initiated. |
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Term
| what is the kitchen appliance comparison for the mouth and stomach? |
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Definition
| mouth: chopping board, stomach: blender |
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Term
| what is the function of the endocrine pancreas? |
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Definition
| synthesis, storage, and secretion of the hormones *insulin and *glucagon into the venous circulation that drains the pancreas |
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Term
| what are the functions of the exocrine pancreas? |
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Definition
| production/delivery of HCO3- to neutralize acidic chyme (pH of 2) coming from the stomach and production/delivery of digestive enzymes to continue digestion in the small intestine |
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Term
| what digestive enzymes are produced in the exocrine pancreas and what is their function? |
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Definition
| *amylase, which digests starch/glycogen. *lipase/colipase, which digest *triaglycerols/phospholipids, and *tripsin/elastase/chymotrypsin which digest peptides/proteins. these are all produced in their inactive pro- form, and become activated when they reach the small intestine |
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Term
| what is the function of the gall bladder? how is it stimulated to action? |
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Definition
| the gall bladder is responsible for storage and release of bile which is produced in the liver. when lipids/proteins are sensed in the small intestine, *cholecystokinin* is released along with lipases from the pancreas to aid in their digestion |
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Term
| what is the major site of digestion in the body? |
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Definition
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Term
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Definition
| a hormone which signals the secretion of HCO3- to neutralize low pH |
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Term
| what are the 3 forms of digestion in the small intestine? |
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Definition
| *intraluminal digestion (w/in the lumen of the small intestine), *enterocytes (between absorptive cells on the brush border) and intracellular digestion (w/in cells) |
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Term
| what are the digestive enzymes of the small intestinal surface and their substrate? |
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Definition
| maltase (maltose), sucrase (sucrose), amylase (amylose), B-glucosidase (glucosylceramide), lactase (lactose), endopeptidase (protein), y-glutamyl transferase (glutathione + amino acid), enteropeptidase (trypsinogen), and alkaline phosphatase (organic phosphates) |
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Term
| what is the purpose of the brush border of the small intestine? |
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Definition
| the brush border is the *site absorption of nutrients* which is enhanced via increased surface area created by villi and microvilli which house many enzymes and lacteals (lymph channels which carry fat soluble vitamins out) |
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Term
| what are the functions of the large intestine? |
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Definition
| digestion of whatever is not digested in the small intestine, such as indigestible carbs (fibers), storage of waste products for up to 24-48 hrs, and absorption of water/electrolytes |
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Term
| how are "undigestable" fibers broken down in the larger intestine? |
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Definition
| anaerobic bacteria break down fibers into short and medium chain FAs which are sent to the liver and used for beta oxidation and energy |
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Term
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Definition
| "good bacteria" like lactobacillus which replenishes those found in the large intestine |
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Term
| what are the functions of blood and lymph in digestion? |
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Definition
| blood travels through the GI tracts and picks up most water-soluble nutrients/fluids that are absorbed through the mucosal membranes of the small intestine. lymphatic vessels pick up most lipids/fat soluble vitamins/fluids that have escaped from the cardiovascular system |
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Term
| what are some of the general functions of the liver? |
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Definition
| the liver is the site for bile formation and secretion by heptocytes and that hepatic bile is then concentrated and stored in the gallbladder and emptied into the duodenum |
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Term
| what organs of the GI are essential/nonessential? |
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Definition
| the *pancreas and *small intestine are essential for digestion/absorption while gastric (stomach) digestion is nonessential for adequate nutrition |
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Term
| what are the 2 forms of active nutrient transport in the GI? |
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Definition
| transcellular, or through the cells and paracellular, which is through the tight junctions between the cells |
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Term
| if nutrients are transported transcellularly across GI epithelium, what 2 membranes must they cross? |
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Definition
| nutrients traveling transcellularly have to cross the *luminal plasma membrane, through the enterocyte and then through the *contra luminal plasma membrane |
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Term
| what is found on the luminal plasma membrane? |
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Definition
| microvilli, brush border, peptidase, oligosaccharides, nutrients, transport proteins and chyme |
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Term
| what is found on the contra luminal plasma membrane? |
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Definition
| mainly Na+/K+ ATPase, adenyl cyclase, few microvilli, intracellular enzymes, capillaries, and lymph (less enzymes overall) |
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Term
| what is the time for digestion in the mouth, esophagus, stomach, sm intestine, lg intestine? |
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Definition
| mouth: seconds, esophagus: seconds, stomach: 3.5 hrs, sm intestine: 5 hrs, lg intestine: 12-24 hrs |
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Term
| what is the progression of proteins as they move through the GI and become amino acids? |
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Definition
| polypeptides ->(pepsin, trypsin, chymotrypsin, elastase)-> free AAs and oligopeptides ->(endopeptidase, aminopeptidase, dipeptidase)-> free AAs and dipeptides/tripeptides ->(carried intracellularly by Na+ pumps and broken down by di/tripeptidase) -> free AAs, which are carried out of the enterocytes into the bloodstream by Na+/K+ pumps |
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Term
| what is the progression of carbohydrates (starch, lactose, sucrose) as they move through the GI and become glucose/galactose/fructose? |
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Definition
| starch is broken down by amylase in the lingual phase into maltose, dextrin, and trisaccharides, which then at the brush border in the small intestine and are broken down by alpha-glucosidases to form glucose. lactose is broken down by lactase at the brush border to form galactose and sucrose is broken down by sucrase to form fructose at the brush border. |
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Term
| how are the breakdown products of carbohydrates transported at the small intestine brush border? |
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Definition
| galactose and glucose are brought intracellularly by SGLT-1 while fructose is brought intracellularly by GLUT-5. all three are brought out of the cell, into the bloodstream by GLUT-2 |
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Term
| how are lipids digested and absorbed? |
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Definition
| in the lumen of the small intestine, triacylglycerol emulsifies and is then broken down by bile acid, lipase and colipase to produce fatty acid 2-monoacylglycerol micelles. smaller micelles (medium chain FAs) can be directly absorbed through the enterocytes and into the blood stream. larger micelles (long chain FAs) are packaged into chylomicrons, which are then released by the enterocytes into the bloodstream |
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Term
| what processes occur in the stomach related to absorption/digestion of vitamins? |
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Definition
| vitamins are released in the stomach by the process of bolus breakdown, intrinsic factor is released by parietal cells which is necessary for vit B12 absorption and HCl reduces Fe3+ iron to Fe2+, which is necessary for Hb formation |
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Term
| what processes occur in the liver related to absorption/digestion of vitamins? |
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Definition
| the liver produces bile, which is necessary for absorption of fat-soluble vitamins (which ultimately are absorbed in the liver) |
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Term
| what processes occur in the pancreas related to absorption/digestion of vitamins? |
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Definition
| digestive enzymes released by the pancreas help to further the release of fat soluble vitamins, esp vit A |
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Term
| where does the majority of vitamin digestion/absorption occur? |
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Definition
| the small intestine...surprise. fat soluble vitamns are absorbed along with dietary fat |
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Term
| what processes occur in the large intestine related to absorption/digestion of vitamins? |
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Definition
| bacteria in the large intestine are responsible for vit K and biotin production, which are then absorbed |
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Term
| what is peptic ulcer disease? |
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Definition
| excessive gastric juice creates a wound in the wall of the GI tract (stomach or duodenum). it can be related to stress, NSAIDs useage and 90% of pts are infected with H. pylori |
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Term
| what causes heartburn/GERD? |
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Definition
| loosening of the lower esophageal sphincter leads to chyme backing up and burning the non-protective surfaces of the esophagus |
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Term
| what are common disorders of carbohydrate digestion? |
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Definition
| lack of lactase enzyme, which declines w/age or can be due to damage to absorption cells. deficiency in carb transport, due to lack of SGLT or GLUT-1 (cannot transport simple sugars into enterocyte). lack of GLUT-1 deficiency syndrome is characterized by infants seizures/delay of motor/mental development - to which a ketogenic diet is the solution (high lipids, low carbs, low protein) |
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Term
| what are disorders of protein digestion/malabsorption? |
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Definition
| deficiency of pepsinogen, trypsinogen, and enteropeptidase (rare) OR defects in neutral amino acid transport: *hartnup disease*, which occurs in the small intestines and kidney and leads to pellagra-like skin (light sensitive dermatitis eruptions), gross aminoaciduria, cerebellar ataxia, and psychosis. hartnup disease is due to a tryptophan transport defect, causing both a niacin and serotonin deficiency |
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Term
| what is an indicator of lipid malabsorption? what could this be due to? |
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Definition
| steatorrhea (excess fat in feces) is an indicator of lipid malabsorption, which can be due to impairment in lipolysis, micelle formation, absorption, chylomicron formation, and transport of chylomicrons via lymph to blood |
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Term
| what is rapid gastric emptying? what can cause it? |
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Definition
| a reduction in the efficiency of lipid interaction w/bile and pancreatic secretions. it can be the result of gastrectomy (as in tx of stomach ulcer or CA) |
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Term
| what might lead to overly-acidic duodenal pH? |
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Definition
| inactivation of pancreatic lipase and decreased ionization of bile acids - as seen in *zollinger-ellison syndrome (due to tumors in the pancreas/duodenum called gastrinomas that secrete gastrin, leading to peptic ulcers) |
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Term
| what is the effect of delayed CCK release? what might cause this? |
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Definition
| delayed CCK release can result in deficiency of bile and pancreatic secretions and is associated with mucosal destruction, regional enteritis and gluten enteropathy |
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Term
| what can lipase/colipase deficiency result in? |
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Definition
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Term
| what happens with pancreatic insufficiency? |
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Definition
| defective lipolysis, like that seen in chronic pancreatitis and pancreatic duct obstruction (CF) |
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Term
| what happens with absent or decreased bile salts? |
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Definition
| decreased lipolysis due to impaired micelle formation |
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Term
| what are general malabsorption problems? |
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Definition
| cholesterol stone (cholelithiasis), cystic fibrosis, celiac disease, and A-B-lipoproteinemia |
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Term
| what is cholesterol stone? |
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Definition
| when the pancreatic bile duct is obstructed b/c of a stone and hormones cannot be released |
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Term
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Definition
| pts cannot digest proteins (glutens) in rye, barley, wheat |
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Term
| what is A-B-lipoproteinemia? |
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Definition
| a deficiency in any protein that has the A-beta, such as LDL, chylomicrons, ec |
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