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Physiology 2 > Small Intestine > Flashcards

Small Intestine Flashcards

1
Q

pancreas produces (generally)

A

hydrolytic enzymes and high volume bicarbonate rich solution

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2
Q

liver and gallbladder generally produce

A

bile (fat absorption)

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3
Q

hydrolytic enzymes in the pancreas are produced by

A

acinar cells

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4
Q

bicarbonate rich high volume solution is produced by

A

duct cells

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5
Q

acinar cells are rich in ER because

A

they produce vast quantities of digestive enzyme

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6
Q

bicarbonate secretion players

A

Cl/HCO3 antiport pushes HCO3 out, Cl in
CFTR maintains luminal Cl concentration
HCO3 is imported by Na/HCO3 cotransporter and made internally by carbonic anhydrase
the resultant H+ is removed by a Na/H exchange on the basolateral membrane
Na and H2O also enter the lumen paracellularly

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7
Q

regulation of bicarbonate secretion is done at the level of the

A

CFTR channel

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8
Q

Cephalic phase of pancreatic secretion

A

enzymes are released following vagal stimulation that causes ACh, VIP, GRP and to some extent gastrin; bicarbonate release from the duct cells is somewhat affected

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9
Q

Gastric phase duodenal secretion

A

vago-vagal stimulation further the release of enzymes

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10
Q

intestinal phase duodenal secretion

A

most pancreatic enzyme release happens here; signal is chyme entering the duodenum, specifically H+, fatty acids longer than 8C, protein digestion products

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11
Q

intestinal phase response is via… (mechanism)

A

endocrine and neurocrine pathways

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12
Q

secretin comes from, is stimulated by, and stimulates… cells that produce it are located in the..

A

Protons stimulate S cells to release secretin which stimulates HCO3 and water release from duct cells
S cells are found in the duodenal mucosa

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13
Q

protons promote what in addition to the release of secretin?

A

activation of a vago-vagal reflex that stimulates additional release of enzymes and bicarb/H2O

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14
Q

what do fat and peptides cause the release of?

A

CCK-RP (paracrine) from epithelial cells which causes release of CCK from I cells in the duodenal mucosa

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15
Q

what besides CCK-RP causes CCK release? where is it released from?

A

monitor peptide released from pancreatic acinar cells

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16
Q

what does CCK do?

A

promotes the effects of secretin and ACh on duct cells (to increase the release of HCO3 and H2O)

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17
Q

promotion of bicarb release in the duct cells is mediated by which three modifiers? how are they different?

A

secretin, CCK, ACh
secretin is the Gs
CCK and ACh are Gq and Gi respectively

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18
Q

bile functions

A

emulsification of fats, solubilization of fat digestive products, elimination of non-soluble by-products (including bilirubin)

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19
Q

what percentage of the bile is recovered following a bile bolus?

A

95%

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20
Q

composition of bile in the gall bladder

A 
70/20/5/1/4
bile acid/bile salt
phospholipids
cholesterol
bilirubin
everything else
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21
Q

primary bile acids

A

cholic acid and chenodeoxycholic acid

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22
Q

secondary bile acids

A

lithocholic acid and deoxycholic acid

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23
Q

what feature of bile acids makes them more soluble than cholesterol?

A

carboxylic acid groups with a high pKa

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24
Q

conjugated bile acids are conjugated with…

A

glycine or taurine and are salts with Na

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25
synopsis of bilirubin removal
bilirubin is produced by the reticuloendothelial system during the breakdown of the heme part of hemoglobin; it is bound to albumin and shipped to the liver where it is excreted in the bile to be eliminated with feces or urine as stercobilin or urobilin
26
what is BSEP?
bile salt export pump
27
what does BSEP do?
export bile salts against a gradient
28
what transports bilirubin
MRP2
29
movement of the bile acids and other bile components draws what? how? what does this do to bile tonicity?
water and electrolytes via leaky tight junctions (paracellularly); bile is isotonic (to plasma)
30
bile acid dependent bile secretion is what?
secretion of the electrolyte laden bile acid solution from hepatocytes along with bile acids; constitutive in humans
31
bile acid independent bile secretion is caused by what? secreted from where?
secretin, VIP, glucagon; release of bicarbonate rich solution; cholangiocytes
32
cholangiocytes can also do what?
resorb water under the right conditions
33
what forms micelles in the bile? how big are they?
bile salts; they are amphipathic; 40-70 angstroms
34
micelles form above what arbitrary line?
critical micelle concentration
35
formation of gallstones is called? blockage?
cholelithiasis; cholestasis
36
gallbladder secretion is controlled by? fires during?
vagal stimulation (ACh release) and CCK release; occurs during the intestinal and cephalic phases
37
fate of bile acids after digestion? 3
1) reabsorption as bile salt through ASBT 2) reabsorption as unconjugated bile acid through membrane diffusion 3) elimination
38
bile acid pool is how big? weight
3 g (elimination is 0.3-0.9/day)
39
membrane bound digestive enzyme
maltase, sucrase, lactase, isomaltase, trehalase, peptidases
40
luminal enzymes
lipases, amylase, carboxypeptidase (A&B), trypsin, chymotrypsin, elastase, cholesterol esterase, pepsin
41
plant complex sugars are... | animal complex sugars are...
amylopectin | amylase
42
carbohydrate digestion
luminal amylase in mouth starts but is inactivated by pH in stomach luminal pancreatic amylase cleaves alpha-1,4 linkages membrane bound carbases finish the job (alpha 1.6 linkages and disaccharide cleavage)
43
glucose uptake is facilitated by
GLUT5 and SGLT on the apical membrane | GLUT 2 on the basal membrane
44
examples of endoproteases
trypsin, pepsin, chymotrypsin, elastase
45
most proteases are converted from their zymogenic form by | which can also be activated by...
trypsin, enterokinase
46
amino acids must be broken down to what level to be absorbed?
di and tri peptides are absrobed most easily
47
PepT1 does what?
imports oligopeptides
48
oligopeptides are broken down to their constituent amino acids where?
inside epithelial cells
49
most dietary fats are in the form of....
triglycerides, cholesterol esters with lesser amounts of phospholipids
50
what keeps the emulsification going in the duodenum?
digestion products, denatured proteins
51
what does colipase do?
binds to a lipase molecule to help it displace a bile acid
52
what is the product of lipase digestion?
mixed micelles full of long chain fatty acids, these mixed micelles are in solution
53
where do the mixed micelles go to deposit the fatty acids?
unstirred aqueous layer above the apical membrane
54
what protein may have a role in transporting cholesterol across the apical membrane
NPC1L1 (along with the removal properties of ABCG5/8)
55
importer of folate is called what?
PteGlu1 (untransformed folate) is imported by SLC19A1
56
how much of the following do you need a day?
Ca - 1000mg/day Fe - 10 mg/day I - 0.1 mg/day
57
pathologically increased peristaltic activity mimics what?
diarrhea
58
pathologically decreased peristaltic activity mimics what?
GI blockage
59
Migrating motor complex; what causes it?
proximal to distal peristaltic waves that occur during fasting; brought on by motilin
60
toxic substances cause what to happen in the intestine?
giant migrating complexes

Physiology 2 (15 decks)

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