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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
Q

synopsis of bilirubin removal

A

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
Q

what is BSEP?

A

bile salt export pump

27
Q

what does BSEP do?

A

export bile salts against a gradient

28
Q

what transports bilirubin

A

MRP2

29
Q

movement of the bile acids and other bile components draws what? how? what does this do to bile tonicity?

A

water and electrolytes via leaky tight junctions (paracellularly); bile is isotonic (to plasma)

30
Q

bile acid dependent bile secretion is what?

A

secretion of the electrolyte laden bile acid solution from hepatocytes along with bile acids; constitutive in humans

31
Q

bile acid independent bile secretion is caused by what? secreted from where?

A

secretin, VIP, glucagon; release of bicarbonate rich solution; cholangiocytes

32
Q

cholangiocytes can also do what?

A

resorb water under the right conditions

33
Q

what forms micelles in the bile? how big are they?

A

bile salts; they are amphipathic; 40-70 angstroms

34
Q

micelles form above what arbitrary line?

A

critical micelle concentration

35
Q

formation of gallstones is called? blockage?

A

cholelithiasis; cholestasis

36
Q

gallbladder secretion is controlled by? fires during?

A

vagal stimulation (ACh release) and CCK release; occurs during the intestinal and cephalic phases

37
Q

fate of bile acids after digestion? 3

A

1) reabsorption as bile salt through ASBT
2) reabsorption as unconjugated bile acid through membrane diffusion
3) elimination

38
Q

bile acid pool is how big? weight

A

3 g (elimination is 0.3-0.9/day)

39
Q

membrane bound digestive enzyme

A

maltase, sucrase, lactase, isomaltase, trehalase, peptidases

40
Q

luminal enzymes

A

lipases, amylase, carboxypeptidase (A&B), trypsin, chymotrypsin, elastase, cholesterol esterase, pepsin

41
Q

plant complex sugars are…

animal complex sugars are…

A

amylopectin

amylase

42
Q

carbohydrate digestion

A

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
Q

glucose uptake is facilitated by

A

GLUT5 and SGLT on the apical membrane

GLUT 2 on the basal membrane

44
Q

examples of endoproteases

A

trypsin, pepsin, chymotrypsin, elastase

45
Q

most proteases are converted from their zymogenic form by

which can also be activated by…

A

trypsin, enterokinase

46
Q

amino acids must be broken down to what level to be absorbed?

A

di and tri peptides are absrobed most easily

47
Q

PepT1 does what?

A

imports oligopeptides

48
Q

oligopeptides are broken down to their constituent amino acids where?

A

inside epithelial cells

49
Q

most dietary fats are in the form of….

A

triglycerides, cholesterol esters with lesser amounts of phospholipids

50
Q

what keeps the emulsification going in the duodenum?

A

digestion products, denatured proteins

51
Q

what does colipase do?

A

binds to a lipase molecule to help it displace a bile acid

52
Q

what is the product of lipase digestion?

A

mixed micelles full of long chain fatty acids, these mixed micelles are in solution

53
Q

where do the mixed micelles go to deposit the fatty acids?

A

unstirred aqueous layer above the apical membrane

54
Q

what protein may have a role in transporting cholesterol across the apical membrane

A

NPC1L1 (along with the removal properties of ABCG5/8)

55
Q

importer of folate is called what?

A

PteGlu1 (untransformed folate) is imported by SLC19A1

56
Q

how much of the following do you need a day?

A

Ca - 1000mg/day
Fe - 10 mg/day
I - 0.1 mg/day

57
Q

pathologically increased peristaltic activity mimics what?

A

diarrhea

58
Q

pathologically decreased peristaltic activity mimics what?

A

GI blockage

59
Q

Migrating motor complex; what causes it?

A

proximal to distal peristaltic waves that occur during fasting; brought on by motilin

60
Q

toxic substances cause what to happen in the intestine?

A

giant migrating complexes

Physiology 2 (15 decks)

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