Pancreatic and biliary activity Flashcards
(172 cards)
1
Q
where do accessory organs lie?
A
These exocrine organs lie outside the digestive tract
and empty their secretions through ducts into the
digestive tract lumen.
2
Q
what makes up the billary system?
A
- Liver
- Gall bladder
3
Q
what are the accessory digestive organs?
A
- Salivary glands
- Billiary system (liver, gall bladder)
- Exocrine pancreas
4
Q
When chyme is released into duodenum, it is mixed with
A
secretions from the small intestine, liver, and exocrine pancreas within the duodenal lumen
5
Q
what is the pancreas?
A
Elongated gland that lies behind and below the stomach and above the first loop of the duodenum – contains both exocrine and endocrine tissue.
6
Q
what are acini?
A
grape like clusters of secretory cells that form sacks
7
Q
what are islets of langerhan?
A
isolated endocrine tissue
8
Q
what do endocrine organs secrete?
A
regulatory hormones
9
Q
what regulatory hormones are secreted by endocrine?
A
insulin, C-peptide, glucagon, somatostatin,
amylin, pancreatic polypeptide
10
Q
exocrine pancreas secretes fluid from two components.
What are they?
A
- Dust cells
- Acinar cells
11
Q
what do acinar cells secrete?
A
Pancreatic digestive enzyme.
12
Q
where are pancreatic digestive enzymes secreted?
A
zymogen granules
(secretory vesicles)
13
Q
zymogen granules released by
A
exocytosis
14
Q
Like pepsinogen, pancreatic enzymes are stored within…
A
… zymogen granules
15
Q
Like pepsinogen, pancreatic enzymes are stored within zymogen granules and released by
A
exocytosis as needed
16
Q
acinar cells secrete how many families of enzymes?
A
secrete 3 families of enzymes
17
Q
Acinar cells secrete 3 families of enzymes:
A
- Proteolytic enzymes
- Pancreatic amylase
- Pancreatic lipase
18
Q
what is the function of Proteolytic enzymes?
A
for protein digestion (proteolysis)
19
Q
function of pancreatic amylase
A
for carbohydrate digestion
20
Q
function of lipase
A
for fat digestion
21
Q
acinar cells also scerete?
A
co-lipase - works with bile to increase lipase activity
22
Q
why are pancreatic enzymes important?
A
These enzymes are important as they can almost completely digest
food in the absence of all other digestive secretions
23
Q
pancreatic acini secrete what juice?
A
pancreatic juice
24
Q
what are the 3 major classes of pancreatic proteolytic enzymes?
A
1) Trypsinogen
2) Chymotrypsinogen
3) Procarboxypeptidase
25
trypsinogen converted into
trypsin
26
how is trypsin activated?
Activated by enteropeptidase / enterokinase – an enzyme imbedded in the luminal membrane of the duodenal mucosa
27
Chymotrypsinogen is converted into
chymotrypsin
28
Chymotrypsinogen converted to chymotrypsin by...
... activated trypsin
29
Procarboxypeptidase is converted to
carboxypeptidase
30
Carboxypeptidases cleave
peptide bonds at the carboxyl terminus of amino
acid residues.
31
what is the result of Pancreatic Proteolytic Enzymes?
mixture of small peptides and amino acids.
32
Mucus secreted by intestinal cells prevents
against digestion of small intestine
wall
33
describe Pancreatic Amylase – Carbohydrate digestion
1) Dietary starches (polysaccharides, amylose, amylopectin)
2) glucose, maltose, sucrose, lactose, a limit dextrins
34
Amylase secreted in
active form as it does not endanger secretory cells
35
salivary amylase breaks down
starch + glycogen
36
salivary amylase breaks down starch and glycogen into
Short chain polysaccharides and disaccharides (maltose, lactose, sucrose)
37
pancreatic amylase breaks down
Short chain polysaccharides and disaccharides (Maltose, Lactose, Sucrose)
38
Pancreatic Amylase breaks down Short chain polysaccharides and disaccharides (Maltose, Lactose, Sucrose) into...
... Short chain Polysaccharides and Disaccharides (Maltose, Lactose, Sucrose, α-Limit Dextrins)
39
what does maltase, lactase, sucrase and a-limit dextrase break down?
... Short chain Polysaccharides and Disaccharides (Maltose, Lactose, Sucrose, α-Limit Dextrins)
40
Maltase, Lactase, Sucrase,
α-Limit Dextrinase breaks down Short chain Polysaccharides and Disaccharides
(Maltose, Lactose, Sucrose, α-Limit Dextrins) into...
... Monosaccharides (Glucose, fructose, Galactose).
Then absorbed via Intestinal capillaries & hepatic portal system to liver
41
42
pancreatic lipase is the main...
... eenzyme secreted by the digestive system that can digest fat.
43
pancreatic lipase hydrolyses...
... triglycerides into monoglycerides and free fatty acids
44
Lipase is also secreted in
an active form as it does not endanger the secretory cells.
45
what makes up a triglyceride?
- glycerol
- 3 fatty acid chains
46
what breaks down fats?
Lingual Lipase
47
Lingual Lipase breaks down fats into...
... Triglycerides to Diglyceride and 1 free FA
48
what does gastric lipase break down?
Triglycerides to Diglyceride and 1 free FA
49
gastric lipase breaks down Triglycerides to Diglyceride and 1 free FA into...
... Triglycerides to Diglyceride and 1 free FA
50
what do bile salts + pancreatic lipase break down?
Triglycerides to Diglyceride and 1 free FA
51
bile salts + pancreatic lipase break down Triglycerides to Diglyceride and 1 free FA into...
Triglycerides and Diglycerides to Monoglycerides
& free FAs (long/short chain)
52
Triglycerides and Diglycerides to Monoglycerides
& free FAs (long/short chain) are broken down by...
... bile salts into micelles.
53
digested fats are fianllly...
... absorbed via intestinal capillaries & hepatic portal system to liver
54
When pancreatic enzymes are deficient →
digestion is incomplete
55
pancreati clipase =
70 % of total lipase activity
56
Pancreatic enzyme deficiency causes
serious maldigestion and malabsorption
57
what is the clinial manifestation of Pancreatic enzyme deficiency?
steatorrhea
58
what is steatorrhea?
Excessive undigested fat in the
faeces
59
What are the symptoms of steatorrhea?
weight loss, abdominal cramps, gas
60
describe the stools of someone with pancreatic insufficiency?
Pale, bulky, foul-smelling, often floating stools, difficult to flush;
may leave oily residue in toilet wate
61
In pancreaatic insufficency, carbohydrates and protein are impaired to lesser degree because of
... salivary, gastric and small intestinal enzymes contributing to digestion
62
cyme entering the duodenum is
highly acidic
63
Chyme entering the duodenum is highly acidic and must be
neutralized quickly, to prevent enzyme denaturation and damage
to the intestinal mucosa
64
Pancreatic duct cells secrete
NaHCO3 (sodium bicarbonate) in duodenal lumen
65
Pancreatic duct cells secrete NaHCO3 (Sodium bicarbonate) in
duodenal lumen → what does this do?
neutralizes the acidic chyme
66
how much NaHCO3 is secreted per day?
1 - 2 L per day
67
NaHCO3: Largest component of
pancreatic secretion
68
Process of alkaline secretion involves
carbonic anhydrase
69
The lipid-permeable CO2 enters the cell through
the basolateral membrane
70
pool for the generation of H2CO3 and HCO3-
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HCO3- leaves the cell via
a luminal anion exchanger.
72
the accumulated Cl- recycles
vial luminal Cl- channels
73
pancreatic secretion is regulated primarily by
hormones secretin and cholecystokinin
74
secretin action
1) acid in duodenum
2) increased secretin released into blood
3) pancreatic duct cells stimulated
4) increase NaHCO3 secreted into duodenal lumen
5) neutralises acid
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Acid in the duodenum
stimulates
the release of secretin
76
secretin is carried int he blood to the
pancreas
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secretin stimulate pancreatic duct cells where they are
stimulated to increase hteir NaHCO3 secretion
78
Increased NaHCO3 secreted into duodenal lumen maintains
the neutrality of the small intestine
79
Cholecystokinin (CCK) regulates....
... pancreatic enzyme secretion
80
Cholecystokinin (CCK) maint stimulus is...
... fat (and to a lesser extent protein) within the duodenum
81
CCK released from duodenal
mucosa where it
travels in the
blood to pancreatic acinar cells to
increase secretions
82
All three types of pancreatic digestive enzymes are...
... packaged together in zymogen granules
(amylase, lipase, protease)
83
the proportion of enzymes released does not
vary
84
the proportion of
enzymes released does not vary
even if
a fatty/protein rich meal is
consumed. Only the total number
of enzymes will vary.
85
CCK action
1) fat / protein in duodenum
2) Increased CCK released into blood
3) Pancreatic acinar cells
4) Increased pancreatic enzymes secreted into duodenal lumen.
86
what are the different functions of the liver?
1. Storage: glycogen, vitamin A & K, Iron
2. Synthesis (Gluconeogenesis)
3. Detoxification (Phase 1 & 2)
4. Hormone production (IGF-1)
5. Hormone inactivation (Insulin)
6. Bile Production
7. Bilirubin production
8. Urea production
9. Cholesterol production
10. Vitamin D activation
11. Drug metabolism
87
liver in direct contact with blood from two sources which are
1) Hepatic artery
2) Hepatic portal vein
88
what is the portal triad made up of?
1. Hepatic arteriole
2. Portal venule
3. One or two small bile ductules
4. Lymphatic vessels
5. Branch of the vagus nerve
89
what are liver sinusoids?
Expanded capillary spaces which run between hepatocytes
* Radiate like spokes linking up parts of the liver
90
what are kupffer cells?
Resident macrophages in the liver
91
what do kupffer cells do?
* Engulf and destroy bacteria and old red blood cells
* Only function not carried out by hepatocyte
92
hepatocyte constantly produces
bile which drains into the bile canaliculus
- This drains to bile duct
93
Hepatic stellate cells are also knonw as?
perisinusoidal cells
94
Pericytes* found in the
perisinusoidal space (AKA space of Disse)
95
what do hepatic stellate cells have in their cytoplasm?
Presence of multiple lipid droplets in their cytoplasm → store vitamin A as retinol ester
96
Hepatic stellate cells are a major cell type involved in...
... liver fibrosis
97
what is liver fibrosis
scar tissue in response to liver damage
98
The bile canaliculus runs between
the cells within the hepatic plate
99
Hepatocytes continuously
secrete
bile
100
Hepatocytes continuously secrete bile (even between meals) into
these thin channels which carries the bile to a bile
duct at the periphery of the lobule.
101
The bile ducts from the various lobules converge
to ....
... eventually form the common bile duct, which transports the bile from the liver to the duodenum.
102
Each hepatocyte is in contact with a ....
... sinusoid on one side and a bile canaliculus
on the other side.
103
what is the ampulla of vater ?
where the bile and pancreatic ducts merge
104
what is the ampulla of vater also knowna s?
hepatopancreatic ampulla
105
Opening of the bile duct into the duodenum is guarded by the
sphincter of Oddi, which prevents bile (& pancreatic secretions) from
entering the duodenum except during digestion.
106
The amount of bile secreted per day is between
250 ml - 1 litre depending on stimulation
107
When the sphincter is closed, bile is diverted into the
gallbladder where it is stored and concentrated between meals
108
what is the gall bladder?
* Small sac-like structure tucked beneath liver
109
the gall bladder is the site of...
... bile storage and concentration between meals
110
Concentration occurs due to
active transport of salt out of the gallbladder, with
water following osmotically → 5-10 times concentration
111
how much bile acids secreted per meal
* 3-15 g of bile acids can be secreted per meal
112
Cholecystokinin (CCK) stimulates the gall bladder to
contract and secrete bile when meal is eaten
113
CCK stimulates relaxation of the
sphincter of Oddi
114
CCK stimulates increased....
... bile secretion by the liver
115
what are gallstones?
precipitation occurs due to increased concentration & prolonged storage of bile salts in the gallbladder → slow progression
116
what is cholelithiasis?
formation of gallstones in the biliary tract, usually in the gallbladder
117
what is Choledocholithiasis?
presence of one or more gallstones in the common bile duct
118
what is Cholecystectomy?
surgical removal of
Gallbladder. Bile is stored in the common bile
duct (which becomes dilated)
119
Cholecystectomy results in
lifestyle changes
120
what is Lithotripsy?
ultrasound shock waves break stones or other calculi (plural of calculus) into particles small enough that can be excreted.
121
bile does not contain any
digestive enzymes
122
Bile does not contain any digestive enzymes, but contains several
... organic constituents that aid in the digestion and absorption of fats
123
Bile does not contain any digestive enzymes, but contains several
organic constituents that aid in the digestion and absorption of fats such as...
- Cholesterol
- Bile salts
- Lecithin
- Bilirubin
- Aqueous alkaline fluid
124
what is cholesterol?
sterol lipid
125
what are bile salts?
derivatives of cholesterol, actively secreted into bile
126
what is Lecithin?
phospholipid
127
what is Bilirubin ?
breakdown product of red blood cells
128
Aqueous alkaline fluid – it is similar to...
pancreatic NaHCO3
129
Most bile salts (95%) are
re-absorbed in the terminal ileum
130
Most bile salts (95%) are re-absorbed in the terminal ileum; with the
remaining 5 % lost in
faeces
131
Most bile salts (95%) are re-absorbed in the terminal ileum; with the
remaining 5 % lost in faeces. They are returned to the...
... liver which re-secrete them.
132
Bile salts act as
detergents (emulsification)
133
Bile salts act as detergents (emulsification): converting...
... large fat lobules into a lipid emulsion -> many small fat droplets suspended in aqueous chyme -> increased surface area.
134
fat droplets =
undigested triglycerides
135
fat droplets are not
water soluble
136
fat droplets must be made
smaller so pancreatic lipase can have access to all
triglycerides, not just those at the surface.
137
bile salts are described as...
... amphipathic (AKA amphiphilic)
138
bile salts have a
lipid soluble part - steroid derived from cholesterol
139
the lipid soluble part of bile salts are...
... hydrophobic (no affinity to water)
140
the water soluble part of bile salts are
hydrophillic (affinity to water).
141
bile salt hydrophillic parts are negatively...
... charged.
142
the two parts of bile salts?
lipid soluble and water soluble part
143
bile salts absorb onto the surface of
the fat glubule - lipid part dissolves into the fat droplet leaving the charged water soluble part projectin
144
* Intestinal movements break up....
... large fat droplets into smaller ones
145
* Intestinal movements break up large fat droplets into smaller ones
* These small droplets would quickly re-coalesce if it wasn’t for...
... bile salts adsorbing on the surface which prevent them from reforming
146
The hydrophilic parts of the bile salts
create a...
shell of negative charge that
repels other negative charges
147
Bile Salts Prevent...
... re-coalescence of fat globules
148
Bile Salts Prevent re-coalescence of fat globules
Creates a greater surface area for ...
... lipase to attack the triglycerides
149
Lipase alone cannot
penetrate the bile salt layer
150
Uses Co-lipase (pancreas) which has both a
lipid-soluble and water soluble component (similar to bile salt)
151
Co-lipase displaces some
bile salts and lodges into the fat globule
152
Co-lipase binds to ...
... lipase anchoring it to the site of action
153
what are the three mechanisms which stimulate bile secretion?
- Chemical mechanisms
- Hormonal mechanisms
- Neural mechanisms
154
chemical mechanisms of stimulating bile secretion?
Bile salts themselves – enterohepatic recirculation – stimulates more bile secretion
155
Hormonal mechanisms of stimulating bile secretion?
Secretin
Cholecystokinin
156
in bile, secretin stimulates?
alkaline bile secretion by liver ducts
157
in bile, Secretin does not
increase bile salt secretion
158
in bile, Cholecystokinin triggered by
presence of food, especially fat in chyme in intestines
159
in bile, cholecystokinin stimulates
gallbladder contraction and bile secretion
160
Neural mechanisms of stimulating bile secretion?
* Vagal stimulation of the liver – minor role
during cephalic phase of digestion
* Increase in liver bile flow before food
reaches stomach or intestine
161
Bilirubin does not play a role in
digestion
162
bilirubin is a waste product actively excreted in
bile
163
what is bile salt?
Yellow bile pigment derived from worn out red blood cells, made from the haem (iron-containing) part of haemoglobin
164
Bilirubin is extracted from
the blood by the hepatocytes and once in the intestine is modified by bacterial enzymes to give the characteristic brown colour of faeces.
165
Small amounts of bilirubin are re-absorbed by
the intestine,
166
Small amounts of bilirubin are re-absorbed by the intestine, where it is
eventually excreted in the urine – largely responsible for the yellow
colour of urine
167
If bile duct is obstructed (e.g
gallstone) faeces become
grayish white
168
If rate of production exceeds
rate of excretion →
increasing level of bilirubin in the blood
169
If rate of production exceeds rate of excretion → increasing
level of bilirubin in the blood →
jaundice
170
Other possible causes of a blocked bile duct include...
... cysts of the common bile duct.
171
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