Pancreatic Secretions U6L03 Flashcards
1
Q
what organ produces the vast majority of digestive enzymes
A
pancreatic
2
Q
protease examples (4)
A
3
Q
what are zymogens?
A
have no enzymatic activity and need to be activated
4
Q
____ is activated to ___by cleavage by enteropeptidase (present in the mucosa of the gut)
A
trypsinogen is activated to trypsin
5
Q
____ cleaves chymotrypsinogen to produce **active chymotrypsin. **
A
trypsin
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.
7
Q
examples of lipases
A
lipase, phopholipase
8
Q
amylases digest
A
carbs
9
Q
nucleases examples
A
ribonuclease
deoxyribonuclease
10
Q
aquous juice is high in
A
bicarbonate, to neurtailize the stomach
11
Q
aqueous juice is produced by
A
duct cells and central acinar cells
12
Q
enzyme juice is produced by ___
A
acinar cells
13
Q
aqueous juice and enzyme juice are examples of ___ secretions
A
exocrine
14
Q
Endocrine secretions of the pancreas are produced in the
A
islets of Langerhans
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).
16
Q
path of pancreatic secretions from the intercalaray ducts?
A
intercalary ducts merge into secretory ducts –> ducts or Wrisung and Santori –> duodenum
17
Q
__ allows for pancreatic enzymes to function at optimal ph
A
bicarbpmate
18
Q
why cant pepsin attack duodenal mucosa?
A
its inactive at neurtal ph
19
Q
___ dilutates the enzyme juice
A
aqueous secretion
20
Q
what is the fundamental secretory unit of the exocine pancreas?
A
acinus and an intercalated duct
21
Q
The ___ cell is a cuboidal cell with abundant mitochondria that secretes bicarbonate
A
duct
22
Q
The zymogen granule protects the pancreas from
A
auto-digestion
23
Q
what happens with enzymes in pancreatitis>
A
enzymes are released into the cell instead of being packaged in granules.
24
Q
The acinar cell has large condensing vacuoles that are gradually reduced in size and form mature ___
A
zymogen granules (which contain proenzymes)
25
\_\_\_\_ increase intracellular calcium in acinar cells (3)
CCK, ACh, and gastrin
26
\_\_\_\_ and ___ increase cAMP in acinar cells (2)
Secretin and VIP
27
Secretin and ___ act synergistically
CCK
28
VIP is a neurotransmitter in the gut normally not important in pancreatic secretion, but it becomes important in
pancreatic tumors known as vipomas, which result in a watery diarrhea.
29
what are vipomas? what NT is important with them?
pancreatic tumor that cause watery diarrhea
VIP
30
Both ___ and ___ stimulate NaCL secretion from the acinar cells
ACh and CCK
31
Both ACh and CCK stimulate NaCl secretion, probably through ____ of basolateral and apical ion channels.
phosphorylation
32
secretion of nacl of the acinar cell does what?
sends water outward
33
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.
CO2
34
Bicarbonate accumulates inside the duct cell and exits across the apical membrane via a\_\_\_exchanger.
Cl-/HCO3-
35
what is the cl channel in the cl/hco3 exchanger?
This chloride channel is the CFTR (Cystic Fibrosis Transmembrane Regulator) channel
36
what ope CFTR (Cystic Fibrosis Transmembrane Regulator) channel? what mechanism does it act?
secretin, utilizing cAMP as its second messenger to open the chloride channel.
The channel only opens when its R domain is phosphorylated by PKA
37
what happens to co2 after it enters the duct cell
hydrated by carbonic anhydrase (CA) to carbonic acid, ---\> which rapidly dissociates to form H+ and HCO3-
38
what happens with the H+ produced after co2 that enters the duct cells is hydrated?
proton **moves across the basolateral membrane**
1. by a **_Na+/H+ exchanger_**
2. or an **_electrogenic proton pump._**
39
what **acidifies _venous blood_** during secretion
**electrogenic proton pump** and by **Na/H exhange in the basolateral membrane** during
40
what stimualtes aquaeous secretion by the pancreatic duct cells
secretin and cck
41
secretin activates ___ channel
cftr cl channel
42
cftr channel replensihes
CL- needed for cl/hclo exchange
43
**CCk** potentiates the action of **secretin** by priming the
NA/K atpase
44
apical K channel is activated by
Ca
45
cck activates via plc to increase
the intracellular ca --\> potentiates action of ca
46
the ___ pathway pulls Na into the tight junctions, allowing water to flow through
paracellular
47
HCO2 exchanges with CL in ducts when
rate of secretion is low
48
pancreas secretes large amounts during ___ of digestion
the intestinal phase
secrete low rate before eating
49
as the rate of secretion increases, the bicarbonate ion concentration is \_\_\_
higher
50
as the rate of secretion increases, the CL ion concentration is \_\_\_
lower
51
The '\_\_\_ hypothesis' accounts for the increase in bicarbonate with increased secretory rate.
exchange
52
effect of pancreatic ducts when CFTR channel is blocked or defective?
he pancreatic ducts become filled with a thick viscous secretion of enzymes.
53
with cystic fibrosis, how was the pancreatic enzyme secretion effected?
thick and vicious, since aquous secretion is needed to dilute
54
pancreatic secretion
1. ____ phase is in reponse to seeing food
cephalic
55
cephalic phase activates the ___ nerve
vagal
56
cephalic phase: vagal stimulation has greater effect on enzyme secretion from acini or ductal aqueous secretion.
acini
57
\_\_\_\_ phase:-distension of body of stomach induces pancreatic enzyme secretion
gastric
58
gastric phase stimulates the __ nerve
vagal
59
antral distension release ___ which stimulates acinar cells to secrete enzymes
gastrin
60
what is released during the intestinal phase?
secretin and cck
61
secretin is released into the blood by ___ cells
s cells
62
secretin inhibits (2)
gastric acid secretion
release of gastrin
63
secretin stimulates the release of
1. pepsinogen
2. aqueous secretion
64
what is secretin high in?
volume
HCO3 content
65
what is secretin low in
enzyme content
66
what is cck released in response from
fatty acids or amino acids entering the duodenum
67
what cells release cck?
l cells
68
cck elicits enzyme secretion by
acinar cells
69
what dtwo things does cck ellicit?
enzyme and aqueous secretion
70
how does cck cause the release of bile?
cck causes gallbladder contraction and relazes the spcinter of odi
71
\_\_\_ causes gallbladder contraction
cck
72
what does bile contain
bile salts
bile pigments
cholesterol
neutral fats
phopsholipids
electrolytes
73
\_\_\_ circulation recycles bile salts
enterohepatic circulation
74
what is the chief bile pigment?
bilirubin
75
The rate limiting step in bile acid formation is the addition of the
hydroxyl group at position 7 by cholesterol 7 alpha-hydroxylase
76
expression of cholesterol 7 alpha-hydroxylase is reduced by
bile acid
77
cholesterol 7 alpha-hydroxylase is increased by \_\_\_
cholesterol
78
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
nuclear hormone
79
why must high levels of bile be regulated?
high lelves have carinogenic properties
80
what is a Choleretic, substance?
timulates the liver to increase output of bile
81
the liver secretes bile \_\_\_
salts
82
The liver conjugates ___ with glycine or taurine to their respective bile salts.
primary and secondary bile acids
83
what is bile salt?
bile acid + conjugate amino acid
84
bile salts are conjugated with mostly
glycine (75%) and taurine (25)
85
conugate bile salts are ____ at a neutral Ph and are water soluble
anionic
86
bile salts are \_\_\_phipathic
amphiphatic
87
why do bile salts need to be amphipathic?
helps them emulsify and soluble ingested fats and steroids
88
-OH groups and ionized groups make bile salts
water soluble
89
Non-conjugated bile salts have a pK of
ca. 7
, i.e., at a pH of 7 only half are ionized, i.e., only half are effective amphipaths.
90
\_\_\_ conjugates have a pK of 3.7
Glycine
91
\_\_\_ conjugates have a pK of 1.5.
taurine
92
how does secondary compared to promary bile salts?
secondary is less soluble
93
\_\_\_make bile salts less water soluble by deconjugating it
intestinal bacteria
94
bile is made by the liver and secreted into ___ before the bile ducts
bile canaliculi
95
pathway of boile from the bile ducts to the ball bladder?
Bile ducts → hepatic ducts → common bile duct → duodenum cystic duct → gall bladder
96
when can bile flow freely into the duodenum?
When the sphincter of Oddi is open bile
97
amount of bile secreted by the liver?
amount of bile in total bile salt pool?
secreted by liver -- 12-25g
total bile salt pool -- 3-4g
98
bile salts are reabsorbed and secreted ___ during a meal
twice
99
how much bile is lost in the feces?
.5g
100
The body makes about 800 mg of cholesterol every day and about \_\_\_% of that is used to make bile salts.
50
101
Bile returns to the liver in what state?
bound to albumin
102
role of** ****sodium taurocholate cotransporting polypeptide**and**organic anion transporting polypeptide**
receptors that take up bile into the liver
103
bile acid depdentent secretion is by \_\_l cells
hepatic parenchyma
104
Most bile acid are reabsorbed as conjugated bile salts (BA-Z-) in the\_\_\_
terminal ileum
105
why do Certain bile constituents concentrate in the gallbladder
(1) the active transport of Na+, Cl- and HCO3- out of the lateral membranes of gallbladder epithelial cells
(2) continued micellar formation.
106
what responds to cephalic stimuli?
botht eh gallblader and stomach
107
gallbladder emptying is stimulated by
vagus
cck
108
bile salts form \_\_- when concentrated
micelles
109
what are micelles made of
bile salts, lecithin and cholesterol
110
. Above the critical micelle concentration (CMC) bile salts are spontaneously self associated into
mixed micelles
111
purpose of micelles?
solvents for hydrophobic waste products to be removed from the body and hydrophobic components of the diet to be captured from the intestine.
112
Cholesterol gallstone formation may be divided into three stages:
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
lechin and bile salts tend to make ___ soluble
chiolesterol
114
high cholesgerol and low bile salt conetration could lead to
insoluble bile salts
115
secretion functions
- 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
CCK FUNCTIONS
- 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
