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66 Cards in this Set
- Front
- Back
gastric acid is stimulated by?
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histamine (H2), Ach (M3), and Gastrin(CCKB) on the parietal cell, in the fundus of the stomach
Ach and Gastrin work via Ca++ pathways, Histamine via cAMP |
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What stimulates CCK secretions?
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Fatty Acids and Amino Acids
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How do pancreatic and salivary amylase digest starches?
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attack the alpha 1-4 linkage, of amylose, amylopectin and glycogen
these will digest starches to oligo and disaccarides |
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What linkages are seen in cellulose?
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Beta 1-4
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Where is GLUT 5 in the enterocyte?
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on the ends of the villi, at the apical side, allowing for passive diffusion of fructose into the enterocyte (glucose and galactose need Na+ cotransport)
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What is the SGLT-1 pump?
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Na+ cotransport bringing in glucose and galactose into the enterocyte
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What hormones does the duodenum secrete?
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CCK, Secretin, GIP, HCO3-
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Where is Iron Absorbed?
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Duodenum
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What controls pancreatic secretions?
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Secretin, CCK and the Vagus Nerve
Secretin and CCK are released by the neuroendocrine cells of the duodenum |
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By what mechanism are monosaccarides absorbed into the blood from the enterocyte?
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GLUT 2
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Where are proteins digested?
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in the stomach and small intestine, by proteases
Stomach: beginning with pepsin, completed in small intestine with brush border and pancreatic proteases pepsin is NOT essential for normal protein digestion |
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What is the optimum pH of pepsin?
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1-3 pepsinogen is activated to pepsin
5: pepsin is denatured |
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What is the first step in intestinal protein digestion?
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trypsinogen is cleaved into trypsin by enterokinase (brush border)
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What are the pancreatic proteases?
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trypsinogen, chymotrypsinogen, proelastase, procarboxypeptidase A and B
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What is the function of the pancreatic proteases?
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they hydrolyze dietary protein to amino acids, di, tri, and oligo-peptides.
oligopeptides must be broken down by brush border peptidases |
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In what form(s) can carbohydrates be absorbed? proteins?
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Monosaccarides ONLY
Amino Acids, Di-Peptides, and Tri-Peptides |
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How are amino acids absorbed?
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Much like glucose and galactose; they need Na+ cotransport (there are four separate transporters, one for each type of aa (neutral, acidic, basic, imino))
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How are dipeptides and tripeptides absorbed?
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by H+ cotransporters, once inside the cell, cytosolic peptidase will hydrolyze to aa (some other di and tri will be absorbed into the bloodstream unchanged)
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What are some disorders of protein digestion or absorption?
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If you have a pancreatic enzyme deficiency, or a defect in the intestinal epithelial transporters
Cystic Fibrosis Chronic Pancreatisis Cystinuria (transporter for the dibasic aa is absent)--> failure to absorb the aa, excreted in the feces |
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What is cystinuria?
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Absence of the transporter for the dibasic amino acids in both the GI and the kidney. Thus, no absorption of cystine, lysine, arginine and ornithine
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Where does the digestion of lipids take place?
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Begins in the stomach with gastric and lingual lipase and is completed in the small intestine with pancreatic lipases, cholesterol ester hydrolase and PLA2
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What is the primary emulsifying agent for fat in the stomach? in the small intestine?
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Stomach:gastric and lingual lipases hydrolyze about 10% of ingested TAG to glycerol. In the stomach, the proteins keep the fat droplets from coalescing
Small intestine: bile acids, the rate of gastric emptying is critical for absorption (CCK slows this down to allow for pancreatic enzymes to digest the lipids) |
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What is colipase?
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secreted from the pancreas in the inactive form (procolipase) which is activated by trypsin. It is needed for pancreatic lipase to digest the lipids.
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What are bile salts function?
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Together with lysolecithin and products of lipid digestion surround and emulsify lipids. Colipase displaces bile salts at the lipid-water interface to allow for lipase-colipase binding
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What does PLA2 do?
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hydrolyzes phospolipids to lysolecithin and fatty acids
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What initiates the gastric phase of digestion?
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Distention, acidity, amino acids, and peptides
This stimuli triggers response, both secretory and contractile via short and long neural reflexes, and with gastrin |
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What is gastrin?
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Hormone secreted by G cells in the antrum of the stomach. They are stimulated by the same things that stimulate the gastric phase (distension, acid, amino acids and peptides)
gastrin works on the parietal cells to increase H+ secretion, and to increase the growth of the mucosa, along with increasing the motility |
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Who is in the CCK family?
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CCK, Secretin, motilin and ghrelin
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What percent of vagal fibers are afferent? efferent?
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90% AFFerent
10% EFFerent |
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What afferent nerves are involved in the swallowing reflex?
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V, IX, X
trigem, vagus, glossopharyngeal |
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What efferent nerves act to aid in swallowing?
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V, VII, IX, X, XII
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What kind of esophageal secretions are there?
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Entirely mucoid, derived from simple and compount mucous glands
lubricate, prevents esophageal excoriation |
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When is the free H+ concentration the highest in the stomach?
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When you aren't eating. The free H+ acts as an inhibitor on gastric secretion, by stimulating the D cell to secrete somatostatin to put the brakes on the parietal cell
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What happens to free H+ concentration in the stomach during digestion.
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The food buffers it, so less free H+ lessens the inhibition on gastric secretion via somatostatin
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What is the first phase of acid secretion in the parietal cell?
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Co2 passively diffuses in
CA catalyzes production of H2Co3, which dissociates into H+ and HCO3-; the H+ is ACTIVELY transported into the lumen of the stomach (H+K+ ATPase);HCO3 has a transporter to exchange Cl- from the blood. Cl- follows after the H+, across the parietal cell into the lumen due to the positive luminal charge |
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What gastric cells have canaliculi?
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Parietal Cells, they have microvilli where the proton pumps are located
In the resting state, they are tubovesicular membranes, but in the secreting state, they fuse and expand |
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How does volume affect gastric empyting rate?
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Increased volume, increased motility
think pete after eating a chipotle. poops soon after |
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How does pH affect gastric emptying rate?
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Acidic things take longer; slows the empyting
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How does osmolarity affect gastric emptying rate?
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Hyper and Hypo tonic slow it down
Isotonic is the fastest |
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How does the calorie intake affect gastric empyting rate?
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The amount of calories consumed is linear, and proportional to the amount of time it takes to empty
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What stimulates CCK release?
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AA, Fatty Acids, MONITOR PEPTIDE & CCK releasing peptide ( MP and CCKRP are released from the pancreas, at basal levels (but is degraded by trypsin... so at basal levels, it doesn't stimulate CCK)
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How is HCO3 secreted from the pancreas?
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Secretin induces a bicarb secretion via a HCO3/Cl- exchange. HCO3 is released into the lumen, H+ is sent into the ECF in exchange for Na+; secretin induces an increased number of Cl- channels on the apical side of the cell to bring Cl- into the lumen (via cAMP phosphorylation)
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What transport mechanisms are important in the gallbladder?
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Na+ K+ ATPase, move Na+ from lumen into the outside, which will concentrate bile in the gallbladder
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what is the difference between a bile salt and a bile acid?
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bile acids get conjugated to bile salts (with the addition of glycine or taurine) which makes them soluble & ionized. They can be deconjugated in the small intestine with the removal of the polypeptide.
unconjugated are NOT water soluble; conjugated are |
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Bile Salt Recycling
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95% recycled in the terminal ileum
So the liver only makes as much as is excreted each day |
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How does flow rate affect saliva concentration?
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low flow rates: saliva has high K and HCO3, low Na, Cl
higher flow rates, less time to remove Na & Cl, and to put in K.. so the saliva has plasma like concentrations HCO3 secretion is selectively stimulated when saliva stimulation is secreted |
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What is the alkaline tide?
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When HCO3- is secreted into the blood stream in exchange for Cl- this alkalinizes the blood.. this HCO3- will later be used in the pancreatic secretions to occur
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What is GRP?
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The NT used when the parasympathetic (vagus) nerve innervates the G-cell to secrete gastrin, which will increase parietal cell secretion of H+
GRP=Ach equivalent at the G cell |
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how does somatostatin affect H+ release?
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Direct pathway: inhibits the stimulatory effects of histamine via the cAMP pathway
Indirect:inhibits the release of Histamine and Gastrin |
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Gastric Ulcers
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decreased H+ secretion because it leaks back through the damaged mucosa
Increased Gastrin secretion though, in response to the low H+ levels |
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What is the composition of pancreatic secretion?
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Isotonic
Super High HCO3- normal plasma concentrations of Na+ and K+ very low Cl- pancreatic lipase, amylase and protease |
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How does flow rate affect pancreatic secretions?
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At LOW flow rates, secretions are high in Na and Cl
at HIGH flow rates, secretions are high in Na+ and HCO3 but they are always isotonic |
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What do the ductal cells of the pancreas do?
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Add in HCO3 and take out Cl via HCO3-Cl exchange mechanism in the luminal membrane
H20 moves into the lumen to be a part of the secretions |
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What does secretin do to the pancreas?
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Acts on pancreatic ductal cells to increase HCO3- secretion
secretin is released from the S cells in the duodenum, in response to the H+ coming from the stomach |
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How is bile formed?
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Continuously by the hepatocytes, drains from the hepatocyte into the bile duct, for storage in the gallbladder
primary bile salts are synthesized from cholesterol; in the intestine, bacteria synthesize secondary bile acids; synthesis of new bile acids occurs to replace what is excreted in the feces |
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How are bile salts recycled?
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In the terminal ileum with a na+ bile salt cotransporter, using secondary active transport
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What would happen if you poisoned the Na+K+ pump on the basolateral wall of the enterocyte?
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You wouldn't keep the low intracellular Na concentration that is needed for Na+ to bring in the glucose and galactose via SGLT-1 pump
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What happens if you destroy the chief cells?
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No pepsingogen.. no pepsin.. but protein breakdown can STILL occur
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What is the primary ion secreted into the intestinal lumen?
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Chloride, regulated by cAMP
Na+ follows Chloride passively, with H20 following behind this is how cholera works, it stimulates Cl secretion by ADP ribosylating the alpha stimulatory subunit of the Gs protein, which increases intracellular cAMP which then opens Chloride channels into the lumen |
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Vibrio Cholera
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ADP ribosylates the alpha s subunit of the Gs protein couple to adenyl cyclase, which permanently activates it. This increases intracellular cAMP, which opens Cl channels. Cl- out into the lumen, Na+ and H20 follow, leading to secretory diarrhea
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How are vitamins absorbed?
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Fat Soluble: just like fats
Water Soluble: Na+ dependent cotransport (just like amino acids, or gluose and galactose) Vit b12 is absorbed in the ileum, requiring intrinsic factor loss of this results in pernicious anemia |
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Dysplastic Nevus
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outbreak of brown spots all over
must go to dermatologist once a year to have them looked out, could be precursor for malignant melanoma |
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Pittyriasis Rosa
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herald patch
christmas tree arrangment non pruritic rash, oblong, red on the outside, pale in the middle |
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Malignant Melanoma
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Superficial Spreading (most common)
Lentigo Malignant (least likely to met, see on the face) Nodular ( Acral Melanoma (most aggressive of all malignant melanoma, occurs in black population, look at soles of feet, under nails) Depth of invasion is most important .76 mm, less won't invade, more will |
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Spider Bites
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Black Widow: red hourglass is on the ventral side, the female eats the male after mating
Neurotoxin, that produces tetanus-like symptoms, particularly in the abdomen, painful bite Brown Recluse: violin spider, painless bite necrotoxin that causes an ulcer the most potent toxin in the world |
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Piloerection, sebaceous glands have
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erector pili muscle
androgen receptors |