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P1: GI > Pancreatic Secretions and Control > Flashcards

Pancreatic Secretions and Control Flashcards

1
Q

What do the secretions of the pancreas join with and where?

A

→The secretions from the pancreas join with the secretions from the gallbladder
→via the common bile duct

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2
Q

Where are the pancreatic secretions emptied?

A

→emptied into the duodenum via the Sphincter of Oddi

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3
Q

What are the functional units of the pancreas?

A

→ Acinar cells

→consists principally of pyramidal epithelial cells → digestive enzymes

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4
Q

What do acinar cells do?

A

→ Release enzymes

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5
Q

What are acinar cells connected to?

A

→Duct that secretes bicarbonate

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6
Q

What do the acini form?

A

→Acini form sacs that connect to the ductal tree and empty into the duodenum

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7
Q

What are intercalated ducts made from?

A

→ squamous epithelium

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8
Q

What are interlobular ducts made from?

A

→ Columnar epithelium- goblet cells

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9
Q

What are interlobular ducts made from?

A

→columnar epithelium/goblet cells

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10
Q

What do the ductal cells release?

A

→bicarbonate rich secretions that are identical to salivary secretions
→except that there is a lot more bicarbonate in it.
→This neutralizes acid.

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11
Q

Where do the bicarbonate secretions come from?

A

→ Ductal and acinar cells

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12
Q

What control are bicarbonate secretions under?

A

→ Secretin

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13
Q

What are the enzyme secretions of the acinar cells under?

A

→CCK

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14
Q

What is the pathway that enzymes take?

A

Acini → microvilli→ intercalated duct → intralobular duct → interlobular duct → pancreatic duct

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15
Q

How much fluid does the pancreas secrete per day?

A

→1.5L

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16
Q

What are the pancreatic secretions made from?

A

→Sodium and HCO3- rich juice, albumin, globulin and digestive enzymes

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17
Q

What do acinar cells secrete?

A

→digestive enzymes to break down carbohydrates, fats, proteins and nucleic acids

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18
Q

Why are enzymes secreted as zymogens?

A

→prevent autodigestion

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19
Q

Where does enzyme activation occur?

A

→in the duodenum

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20
Q

What are the anions that are secreted in pancreatic juice?

A

→HCO3-,
→Cl-
→SO42-
→HPO42-

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21
Q

What are the cations that are secreted in pancreatic juice?

A

→Na+
→K+,
→Ca2+
→Mg2+

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22
Q

What do the HCO3- secretions occur?

A

→ Secretions from the gallbladder help to neutralize gastric acid

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23
Q

How is the composition of the juice varied as it moves through the ducts?

A

→The composition of the juice is modified as it travels through the duct : epithelial cells actively exchange Cl-/HCO3-

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24
Q

How does H2CO3 form?

A

→H+ is actively eliminated by Na+/H+ exchanger
→H+ is exchanged for K+ driven by Na+/K+ ATPase
→H+ neutralizes HCO3- (H2CO3 is formed)
→More CO2 and HCO3- is produced in the blood
→CO2 diffuses in and forms H2CO3 with H2O

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25
What is the rate of pancreatic juice production proportional to?
→ [HCO3-]pancreatic juice and its rate of production∝ [HCO3-]blood
26
What happens to Cl- and amylase after you infuse secretin?
→There is reciprocal change in the concentrations of Cl- and HCO3- after the infusion of secretin →reduced amylase and Cl- concentrations upon secretin infusion may be a dilution effect due to volume increase in the pancreatic juice
27
Why does Cl- and amylase decrease after infusing secretin?
→The amount of chloride and amylase decreases | → there are more increased watery secretions so the other components decrease.
28
What are the 3 major types of enzymes?
→Proteolytic enzymes (trypsin, chymotrypsin, carboxypeptidase) →Amylase →Lipase Also →Ribonuclease →Deoxyribonuclease
29
What is the activator and substrate of trypsin?
→A : Secreted as trypsinogen - activated by enterokinase/enteropeptidase and by trypsin →S: Proteins and polypeptides
30
What is the substrate of pancreatic lipase?
→triglycerides
31
What is the activator and substrate of Pancreatic α amylase?
→ A: Cl- | →S: Starch
32
What is the substrate of ribonuclease and deoxyribonuclease?
→ RNA | → DNA
33
What is the activator and substrate of elastase?
→ A: Trypsin | → S: Elastin
34
What is the activator and substrate of Phospholipase A2?
→ A: Trypsin | → S: Phospholipids (lecithin)
35
What is the activator and substrate of carboxypeptidase A+B?
→ A: Trypsin | → S: Proteins and polypeptides
36
What is the activator and substrate of colipase?
→ A: trypsin | → B: fat droplets
37
How are proteolytic enzymes secreted and why?
→Enzymes secreted as proenzymes | → Prevent autodigestion
38
Where is enterokinase and when is it secreted?
→ Brush border of duodenum | → Secreted in response to CCK
39
What does enterokinase do?
→ trypsinogen to trypsin
40
What is meant by an autocatalytic reaction?
→ Once one trypsin is formed it can go on and convert more trypsinogens to trypsin
41
What are inhibitors of autodigestion?
→Kazal inhibitor - enzyme Y (chymotrypsin C, caldecrin) | →Intracellular pH of zymogen granule = acidic (keeps zymogen inactive)
42
What happens in acute pancreatitis?
→Trypsin activates phospholipase A2 in the pancreatic duct | →Increase in pancreatic alpha amylase - diagnostic test
43
What does activation of PLA2 in the pancreatic duct do?
→converts Lecithin → Isolecithin (PLA2) | →Isolecithin → disruption of pancreatic tissue, membrane damage and necrosis
44
What reaction does amylase catalyze?
→polysaccharides → disaccharides
45
What reaction does lipase catalyze?
→triglycerides → fatty acids and glycerol
46
What happens in pancreatic insufficiency?
→poor digestion of lipids and their malabsorption which causes steatorrhoea
47
What is the percentage of the enzymes that reach the small intestine?
→Amylase - 75% →Trypsin - 20% →Lipase - 1%
48
What membranes do chymotrypsinogen and amylase cross in the pancreas and what does this suggest?
→Chymotrypsinogen and amylase cross the basolateral membrane of the pancreas →Suggests bidirectional permeability of the basolateral membrane to digestive enzymes
49
How are pancreatic secretions controlled?
→ Neuroendocrine secretions
50
What happens to pancreatic secretions with parasympathetic stimulation?
→enhances the rate of secretion of enzymes and aqueous components of pancreatic juice
51
What happens to pancreatic secretions with sympathetic stimulation?
→inhibits secretion
52
What do secretin and CCK do?
→ stimulate secretion of pancreatic fluid ( enzyme and bicarbonate rich secretions)
53
What happens during the cephalic phase?
→Vagal (ACh and VIP) stimulation of gastrin release from the antrum → some protein-rich pancreatic juice
54
What happens during the gastric phase?
→Distension (vagal reflex on fundus or antrum) amino acid and peptide ( in antrum) stimulated gastrin secretion → release of enzyme rich pancreatic juice
55
What happens as the result of a vagotomy?
Vagotomy → 50% decrease in response to acidic chyme
56
What happens in the intestinal phase?
→Secretin and CCK →Acidic chyme in the duodenum and jejunum induces secretion of pancreatic juice with bicarbonate in it to neutralize the acid.
57
Where is secretin produced?
→from mucosa of duodenal and jejunum
58
What does secretin induce?
→Induces pancreatic duct cells to secrete HCO3- rich pancreatic juice but decreased enzyme content
59
What does secretin stimulate in the liver?
→ the production of bile by the liver
60
Where is CCK secreted from and in response to what?
→ from duodenal and jejunum in response to fatty acids
61
What does CCK stimulate?
→stimulates pancreatic acinar cells to synthesize and release enzyme rich pancreatic juice →stimulates the secretion of concentrated bile from gallbladder for fat absorption
62
What effect does CCK have on the gallbladder?
→Contracts the gallbladder and relaxes the sphincter of Oddi → release of bile into the duodenum
63
What does CCK potentiate?
→Potentiates the effect of secretin which is a weak agonist of acinar cells
64
What is a consequence of cystic fibrosis?
→The pancreatic ducts are blocked and the intestines cannot absorb nutrients fully →Steatorrhea

P1: GI (15 decks)

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