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PHSL233 > Lecture 31 - Pancreatic and Biliary Secretion > Flashcards

Lecture 31 - Pancreatic and Biliary Secretion Flashcards

1
Q

Where is CCK released from?

A

I-cells in the duodenum due to fat and protein digestive products

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2
Q

What does CCK do?

A

Inhibits gastrin secretion in the antrum (via D-cell)
Increases protein secretion in the pancreatic acini

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3
Q

Where is secretin released from?

A

S-cells in the small intestine due to acidification of the duodenum

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4
Q

What does secretin do?

A

Inhibits gastrin secretion in the antrum (via D-cell)
Increases fluid secretion in the pancreatic duct

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5
Q

What is the structure of the exocrine pancreas?

A

Lobules
- acini
Ducts
- intercalated
- common bile
Secretory units
- acini
- intercalated ducts

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6
Q

What are the secretory cells of the pancreas?

A

Acinus
Intercalated ducts

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7
Q

What is the site of majority of fluid secretion in the pancreas?

A

Duct cells

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8
Q

What do the acinar cells in pancreas secrete?

A

Isotonic NaCl solution - 25% of secretion

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9
Q

What do the duct cells in pancreas secrete?

A

HCO3- rich fluid - 75% of secretion

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10
Q

What is the difference in osmolarity between the saliva and pancreas?

A

Saliva: 100 mOsm
Pancreas: 300 mOsm

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11
Q

What is the volume and composition of secretions from pancreas?

A

1-1.5 L of alkaline fluid and 5 -15 g protein secreted per day

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12
Q

Where are the proteins in pancreatic secretions made?

A

Acinar cells

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13
Q

What proteins do the pancreatic acinar cells secrete?

A

20 different proteins secreted - mainly digestive enzymes
- zymogens - inactive precursors of digestive enzymes
- (trypsinogen, procarboxypeptidase)
- amylase, lipase
Enzymes for all major nutrient groups

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14
Q

What cell produces the alkaline fluid in pancreatic secretion?

A

Intercalated duct cells

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15
Q

What does the alkaline fluid in pancreatic secretion do?

A

Neutralises acidic chyme from the stomach

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16
Q

What is the alkaline fluid in pancreatic secretion?

A

Isosmotic NaHCO3 solution

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17
Q

When do we have the largest volume of pancreatic secretion?

A

Intestinal phase due to CCK and secretin

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18
Q

What stimulates pancreatic secretion?

A

CCK
Secretin
- minor regulation via vagus (ACh)

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19
Q

What stimulates pancreatic acinar cells?

A

CCK and vagus (ACh)

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20
Q

What stimulates pancreatic duct cells?

A

Secretin

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21
Q

Pancreatic secretion
A. is hypotonic due to high Na+ re-absorption in pancreatic ducts.
B. is stimulated by somatostatin.
C. contains trypsinogen released from zymogen granules.
D. is elevated during the gastric phase.

A

C. contains trypsinogen released from zymogen granules.

A - Salivary gland not pancreatic
B - Somatostatin always switch off - not involved with pancreatic secretion
D - Elevated in intestinal phase

22
Q

What are pancreatic acinar cells specialised for?

A

Protein secretion
- zymogen granules

23
Q

How does CCK and ACh stimulate secretion of pancreatic acinar cells?

A

Increase in intracellular Ca2+

24
Q

How do acinar cells secrete isotonic NaCl solution/What is fluid secretion in pancreatic acinar cells driven by?

A

By electrogenic Cl- secretion

25
Q

Why does increase in Ca+ in pancreatic acinar cells increase secretion?

A

By activating a Ca2+ dependent apical Cl- channel (CFTR)
- also stimulates secretion of enzymes

26
Q

What is secretion by pancreatic duct cell dependent on?

A

Dependent on apical Cl-/HCO3- exchanger

27
Q

Why is Cl-/HCO3- exchanger inactive at rest?

A

Due to little Cl- in duct lumen

28
Q

What is Cl- in pancreatic duct lumen controlled by?

A

Controlled indirectly via a cAMP-dependent Cl- channel (CFTR) activated by secretin

29
Q

How does secretin increase pancreatic duct cell secretion?

A

Increasing cAMP
Activation of apical Cl- channel (cAMP-activated)
Increased Cl- in duct lumen
luminal Cl- exchanged for HCO3-
Result: HCO3- secretion

30
Q

Why does Na+ diffuse paracellular in pancreatic duct cells?

A

Due to electric gradient set up by Cl- and HCO3- movement

31
Q

Why do we also have the secretion of NaHCO3 in pancreatic duct cells?

A

Na+ diffuses across the paracellular pathway due to potential set up by Cl- and HCO3- movement
Water follows because of the osmotic gradient

32
Q

The secretion of a bicarbonate-rich solution by pancreatic duct cells is driven by CCK, BECAUSE
bicarbonate secretion in stimulated pancreatic duct cells is facilitated by CFTR.

A

D - First false, second true

Driven by secretin not CCK, CCK for acinar cells

33
Q

What epithelia are the pancreatic duct cells?

A

Leaky

34
Q

What are the differences in salivary and pancreatic duct secretion?

A

Tight vs leaky epithelium
Chloride secreted to drive bicarbonate secretion (boosted by secretin in pancreas)
NO change in sodium content (pancreas)
Major site of fluid secretion in pancreas

35
Q

How does the liver process absorbed nutrients and control metabolism?

A

Gluconeogenesis, glucose buffering, fatty acid oxidation, synthesis of plasma proteins (e.g., albumin)

36
Q

What is the exocrine function of the liver?

A

Secretion and excretion

37
Q

What is secretion and excretion of liver?

A

Provision of bile acids and alkaline fluid to:
- aid digestion and absorption of fats
- neutralise gastric acid
Degradation and conjugation of waste products of metabolism
Detoxification of poisonous substances
Excretion of waste metabolites and detoxified substance in bile

38
Q

What is function of liver assisted by?

A

Blood supply

39
Q

Where is bile secreted in liver?

A

Bile secreted by hepatocytes lining canaliculi

40
Q

What do ducts in liver secrete?

A

HCO3- rich fluid

41
Q

Where is liver secretion stored and concentrated?

A

Gall bladder between meals

42
Q

What is the volume and composition of liver secretion?

A

0.5 L day-1 - secreted continuously
Excretory products
- bile pigments - waste products
- cholesterol - excreted by liver
- steroids, heavy metal, drugs
Products associated with digestion
- HCO3- rich fluid - secreted by duct cells
- bile salts

43
Q

What makes up bile salts?

A

Amphipathic compounds
- hydrophillic and hydrophobic surface
Primary bile acid
- Cholic acid

44
Q

What are the two sources of bile salts in liver secretion?

A

Newly synthesised
Enterohepatic circulation

45
Q

What percentage of bile salts are absorbed in the enterohepatic circulation?

A

95%

46
Q

What is the mechanism of bile salt absorption in the enterohepatic circulation?

A

Small intestine
- limited passive absorption
- active absorption in ileum
Colon
- limited role

47
Q

What are the three mechanisms of biliary secretion?

A

Nervous
Hormonal
Bile salts

48
Q

What is the control of biliary secretion in the cephalic and gastric phases?

A

Minor, PNS

49
Q

What is the control of biliary secretion in the intestinal phase?

A

Hormonal
- secretin stimulates production of HCO3- rich solution by ducts
- CCK stimulates contraction of gallbladder
Bile salts
- arrival of bile salts in portal venous blood stimulates absorption by liver and subsequent secretion

50
Q

The liver produces a bicarbonate-rich bile, BECAUSE bile acids are required to reabsorb protein in the intestine.

A

C - First true, second false
Bile acids to reabsorb fat

51
Q

What stimulates biliary secretion?

A

CCK and secretin

52
Q

What is the purpose of bile acids in biliary secretion?

A

To reabsorb fat

PHSL233 (32 decks)

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