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Physiology > Pancreatic Secretions U6L03 > Flashcards

Pancreatic Secretions U6L03 Flashcards

1
Q

what organ produces the vast majority of digestive enzymes

A

pancreatic

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2
Q

protease examples (4)

A
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3
Q

what are zymogens?

A

have no enzymatic activity and need to be activated

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4
Q

____ is activated to ___by cleavage by enteropeptidase (present in the mucosa of the gut)

A

trypsinogen is activated to trypsin

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5
Q

____ cleaves chymotrypsinogen to produce **active chymotrypsin. **

A

trypsin

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6
Q

In pancreatitis the pancreas becomes inflamed and the digestive enzymes are activated when?

A

before they reach the intestine causing damage to the pancreas.

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7
Q

examples of lipases

A

lipase, phopholipase

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8
Q

amylases digest

A

carbs

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9
Q

nucleases examples

A

ribonuclease

deoxyribonuclease

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10
Q

aquous juice is high in

A

bicarbonate, to neurtailize the stomach

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11
Q

aqueous juice is produced by

A

duct cells and central acinar cells

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12
Q

enzyme juice is produced by ___

A

acinar cells

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13
Q

aqueous juice and enzyme juice are examples of ___ secretions

A

exocrine

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14
Q

Endocrine secretions of the pancreas are produced in the

A

islets of Langerhans

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15
Q

endocrine secretions of the pancreas inclide

A

(1) glucagon (secreted by alpha cells)
(2) insulin (secreted by beta cells)
(3) somatostatin (secreted by delta cells).

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16
Q

path of pancreatic secretions from the intercalaray ducts?

A

intercalary ducts merge into secretory ducts –> ducts or Wrisung and Santori –> duodenum

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17
Q

__ allows for pancreatic enzymes to function at optimal ph

A

bicarbpmate

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18
Q

why cant pepsin attack duodenal mucosa?

A

its inactive at neurtal ph

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19
Q

___ dilutates the enzyme juice

A

aqueous secretion

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20
Q

what is the fundamental secretory unit of the exocine pancreas?

A

acinus and an intercalated duct

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21
Q

The ___ cell is a cuboidal cell with abundant mitochondria that secretes bicarbonate

A

duct

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22
Q

The zymogen granule protects the pancreas from

A

auto-digestion

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23
Q

what happens with enzymes in pancreatitis>

A

enzymes are released into the cell instead of being packaged in granules.

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24
Q

The acinar cell has large condensing vacuoles that are gradually reduced in size and form mature ___

A

zymogen granules (which contain proenzymes)

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25
Q

____ increase intracellular calcium in acinar cells (3)

A

CCK, ACh, and gastrin

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26
Q

____ and ___ increase cAMP in acinar cells (2)

A

Secretin and VIP

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27
Q

Secretin and ___ act synergistically

A

CCK

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28
Q

VIP is a neurotransmitter in the gut normally not important in pancreatic secretion, but it becomes important in

A

pancreatic tumors known as vipomas, which result in a watery diarrhea.

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29
Q

what are vipomas? what NT is important with them?

A

pancreatic tumor that cause watery diarrhea

VIP

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30
Q

Both ___ and ___ stimulate NaCL secretion from the acinar cells

A

ACh and CCK

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31
Q

Both ACh and CCK stimulate NaCl secretion, probably through ____ of basolateral and apical ion channels.

A

phosphorylation

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32
Q

secretion of nacl of the acinar cell does what?

A

sends water outward

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33
Q

in the duct cell

The initial step in bicarbonate secretion by the duct cell is diffusion of ____ from the blood
across the basolateral membrane into the duct cell.

A

CO2

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34
Q

Bicarbonate accumulates inside the duct cell and exits across the apical membrane via a___exchanger.

A

Cl-/HCO3-

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35
Q

what is the cl channel in the cl/hco3 exchanger?

A

This chloride channel is the CFTR (Cystic Fibrosis Transmembrane Regulator) channel

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36
Q

what ope CFTR (Cystic Fibrosis Transmembrane Regulator) channel? what mechanism does it act?

A

secretin, utilizing cAMP as its second messenger to open the chloride channel.

The channel only opens when its R domain is phosphorylated by PKA

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37
Q

what happens to co2 after it enters the duct cell

A

hydrated by carbonic anhydrase (CA) to carbonic acid, —> which rapidly dissociates to form H+ and HCO3-

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38
Q

what happens with the H+ produced after co2 that enters the duct cells is hydrated?

A

proton moves across the basolateral membrane

  1. by a Na+/H+ exchanger
  2. or an electrogenic proton pump.
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39
Q

what acidifies venous blood during secretion

A

electrogenic proton pump and by Na/H exhange in the basolateral membrane during

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40
Q

what stimualtes aquaeous secretion by the pancreatic duct cells

A

secretin and cck

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41
Q

secretin activates ___ channel

A

cftr cl channel

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42
Q

cftr channel replensihes

A

CL- needed for cl/hclo exchange

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43
Q

CCk potentiates the action of secretin by priming the

A

NA/K atpase

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44
Q

apical K channel is activated by

A

Ca

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45
Q

cck activates via plc to increase

A

the intracellular ca –> potentiates action of ca

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46
Q

the ___ pathway pulls Na into the tight junctions, allowing water to flow through

A

paracellular

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47
Q

HCO2 exchanges with CL in ducts when

A

rate of secretion is low

48
Q

pancreas secretes large amounts during ___ of digestion

A

the intestinal phase

secrete low rate before eating

49
Q

as the rate of secretion increases, the bicarbonate ion concentration is ___

A

higher

50
Q

as the rate of secretion increases, the CL ion concentration is ___

A

lower

51
Q

The ‘___ hypothesis’ accounts for the increase in bicarbonate with increased secretory rate.

A

exchange

52
Q

effect of pancreatic ducts when CFTR channel is blocked or defective?

A

he pancreatic ducts become filled with a thick viscous secretion of enzymes.

53
Q

with cystic fibrosis, how was the pancreatic enzyme secretion effected?

A

thick and vicious, since aquous secretion is needed to dilute

54
Q

pancreatic secretion

  1. ____ phase is in reponse to seeing food
A

cephalic

55
Q

cephalic phase activates the ___ nerve

A

vagal

56
Q

cephalic phase: vagal stimulation has greater effect on enzyme secretion from acini or ductal aqueous secretion.

A

acini

57
Q

____ phase:-distension of body of stomach induces pancreatic enzyme secretion

A

gastric

58
Q

gastric phase stimulates the __ nerve

A

vagal

59
Q

antral distension release ___ which stimulates acinar cells to secrete enzymes

A

gastrin

60
Q

what is released during the intestinal phase?

A

secretin and cck

61
Q

secretin is released into the blood by ___ cells

A

s cells

62
Q

secretin inhibits (2)

A

gastric acid secretion

release of gastrin

63
Q

secretin stimulates the release of

A
  1. pepsinogen
  2. aqueous secretion
64
Q

what is secretin high in?

A

volume

HCO3 content

65
Q

what is secretin low in

A

enzyme content

66
Q

what is cck released in response from

A

fatty acids or amino acids entering the duodenum

67
Q

what cells release cck?

A

l cells

68
Q

cck elicits enzyme secretion by

A

acinar cells

69
Q

what dtwo things does cck ellicit?

A

enzyme and aqueous secretion

70
Q

how does cck cause the release of bile?

A

cck causes gallbladder contraction and relazes the spcinter of odi

71
Q

___ causes gallbladder contraction

A

cck

72
Q

what does bile contain

A

bile salts

bile pigments

cholesterol

neutral fats

phopsholipids

electrolytes

73
Q

___ circulation recycles bile salts

A

enterohepatic circulation

74
Q

what is the chief bile pigment?

A

bilirubin

75
Q

The rate limiting step in bile acid formation is the addition of the

A

hydroxyl group at position 7 by cholesterol 7 alpha-hydroxylase

76
Q

expression of cholesterol 7 alpha-hydroxylase is reduced by

A

bile acid

77
Q

cholesterol 7 alpha-hydroxylase is increased by ___

A

cholesterol

78
Q

Bile acids can be thought of as steroid hormones, made by the liver and activating a___ receptor to regulate expression of cholesterol 7 alpha- hydroxylase

A

nuclear hormone

79
Q

why must high levels of bile be regulated?

A

high lelves have carinogenic properties

80
Q

what is a Choleretic, substance?

A

timulates the liver to increase output of bile

81
Q

the liver secretes bile ___

A

salts

82
Q

The liver conjugates ___ with glycine or taurine to their respective bile salts.

A

primary and secondary bile acids

83
Q

what is bile salt?

A

bile acid + conjugate amino acid

84
Q

bile salts are conjugated with mostly

A

glycine (75%) and taurine (25)

85
Q

conugate bile salts are ____ at a neutral Ph and are water soluble

A

anionic

86
Q

bile salts are ___phipathic

A

amphiphatic

87
Q

why do bile salts need to be amphipathic?

A

helps them emulsify and soluble ingested fats and steroids

88
Q

-OH groups and ionized groups make bile salts

A

water soluble

89
Q

Non-conjugated bile salts have a pK of

A

ca. 7

, i.e., at a pH of 7 only half are ionized, i.e., only half are effective amphipaths.

90
Q

___ conjugates have a pK of 3.7

A

Glycine

91
Q

___ conjugates have a pK of 1.5.

A

taurine

92
Q

how does secondary compared to promary bile salts?

A

secondary is less soluble

93
Q

___make bile salts less water soluble by deconjugating it

A

intestinal bacteria

94
Q

bile is made by the liver and secreted into ___ before the bile ducts

A

bile canaliculi

95
Q

pathway of boile from the bile ducts to the ball bladder?

A

Bile ducts → hepatic ducts → common bile duct → duodenum cystic duct → gall bladder

96
Q

when can bile flow freely into the duodenum?

A

When the sphincter of Oddi is open bile

97
Q

amount of bile secreted by the liver?

amount of bile in total bile salt pool?

A

secreted by liver – 12-25g

total bile salt pool – 3-4g

98
Q

bile salts are reabsorbed and secreted ___ during a meal

A

twice

99
Q

how much bile is lost in the feces?

A

.5g

100
Q

The body makes about 800 mg of cholesterol every day and about ___% of that is used to make bile salts.

A

50

101
Q

Bile returns to the liver in what state?

A

bound to albumin

102
Q

role of** sodium taurocholate cotransporting polypeptideandorganic anion transporting polypeptide**

A

receptors that take up bile into the liver

103
Q

bile acid depdentent secretion is by __l cells

A

hepatic parenchyma

104
Q

Most bile acid are reabsorbed as conjugated bile salts (BA-Z-) in the___

A

terminal ileum

105
Q

why do Certain bile constituents concentrate in the gallbladder

A

(1) the active transport of Na+, Cl- and HCO3- out of the lateral membranes of gallbladder epithelial cells
(2) continued micellar formation.

106
Q

what responds to cephalic stimuli?

A

botht eh gallblader and stomach

107
Q

gallbladder emptying is stimulated by

A

vagus

cck

108
Q

bile salts form __- when concentrated

A

micelles

109
Q

what are micelles made of

A

bile salts, lecithin and cholesterol

110
Q

. Above the critical micelle concentration (CMC) bile salts are spontaneously self associated into

A

mixed micelles

111
Q

purpose of micelles?

A

solvents for hydrophobic waste products to be removed from the body and hydrophobic components of the diet to be captured from the intestine.

112
Q

Cholesterol gallstone formation may be divided into three stages:

A

1. supersaturation of cholesterol - occurs in the liver (see diagram above).
2. nucleation and precipitation - seeding of cholesterol crystals or
microstones - probably occurs in the gallbladder - mechanism is
uncertain.
3. growth of microstones to form macrostones

113
Q

lechin and bile salts tend to make ___ soluble

A

chiolesterol

114
Q

high cholesgerol and low bile salt conetration could lead to

A

insoluble bile salts

115
Q

secretion functions

A
  • STIM AQUAOUS SECRETION BY DUCT CELLS
  • INC CAMP IN ACINAR CELLS
  • INHIBITS GASTRIN AND GASTRIC ACID SECRETION

STIM PEPSINOGEN

HIGH IN VOLUME, HCO3 CONTENT

LOW IN ENZYME CONTENT

116
Q

CCK FUNCTIONS

A
  • STIM AQUOUS SECRETION IN DUCT CELLS
  • POTNETIATES ACTION OF SECRETIN
  • INC INTRACELLULAR CA IN ACINAR CELLS

CAUSE NACL SECRETION FROM ACINAR CELLS

CONTRACTS THE GALLBLADDER, CAUSING RELEASE

OPENS THE SPHINCTER OF ODI

117
Q
A

Physiology (5 decks)

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