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W/Physiology > Topic 6.4 > Flashcards

Topic 6.4 Flashcards

1
Q

How much of the pancreatic secretion is endocrine?

A

About 2%

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2
Q

What are the 2 main roles of pancreatic secretion?

A
  • neutralize acid content from the stomach

- digestion using digestive enzymes

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3
Q

How much pancreatic juice is secreted per day?

A

700-900mL / day (depends on ingested food)

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4
Q

What are the characteristics of pancreatic juice secretion? (2)

A
  • Isoosmotic

- Alkaline

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5
Q

What type of secretion mechanism for pancreatic juice?

A

Sequential secretion : both acinar and duct cells will produce PJ (duct > acinar)

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6
Q

What are the 3 main differences between salivary acinar secretion and pancreatic acinar secretion?

A
  • secrete more enzymes than salivary gland, in the inactive form
  • less fluid
  • has CFTR chloride channel
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7
Q

Which of the pancreatic cells produce the majority of the fluid?

A

The duct cells

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8
Q

How do pancreatic duct cells make the pancreatic juice more alkaline?

A

By exchanging CL- for HCO3- (proximally)

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9
Q

What happens in the distal pancreatic duct cells?

A

Some HCO3- can be reabsorbed and exchanged for Cl-, the amount depends on the rate of secretion

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10
Q

What are the 3 ways of regulating pancreatic juice secretion?

A
  • Neural regulation
  • Hormonal regulation
  • Feed forward regulation (look at food)
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11
Q

Which neural regulation dominates pancreatic juice secretion?

A

parasympathetic

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12
Q

How does Ach affect PJ secretion? (3)

A
  • Acts on acinar cells
  • Gq coupled (M3)
  • Upregulates enzyme secretion
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13
Q

How does VIP affect PJ secretion? (3)

A
  • Acts on vessels (or acinar cell)
  • Gs coupled
  • Causes vasodilation to increase volume of secretion
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14
Q

What are the 2 hormones that can affect PJ secretion?

A

CCK and secretin

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15
Q

When is secretin produced?

A

When there is low duodenal pH condition

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16
Q

What is the effect of secretin on pj secretion?

A
  • acts on the duct cells

- increase HCO3- secretion

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17
Q

When is CCK produced?

A

When there is protein degradation / digested food in the stomach

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18
Q

What is the effect of CCK on the pj secretion?

A

will increase the secretion of digestive enzymes (Ca2+ signal)

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19
Q

What is the vagovagal reflex?

A

presence of food in the stomach (or intestine) increases pancreatic juice secretion

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20
Q

How much blood can the liver store?

A

0.5L

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21
Q

What are the 5 main roles of the liver?

A
  1. Metabolic role
  2. Blood reservoir
  3. Store for copper, Fe
  4. Immunological (kupffer)
  5. secretory and excretory functions
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22
Q

What is the secretory fluid of the liver?

A

bile, digestive fluid without proteins

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23
Q

What is the excretory fluid of the liver useful for?

A

removing substances that can’t be removed by kidneys (xenobiotics, heavy metals, drugs)

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24
Q

Bile production / day

A

200-1200mL/day

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25
Q

What are 4 characteristics of the bile?

A
  • Isoosmotic
  • Alkaline
  • Mixture of hepatic and gallbladder bile
  • Micellar formation
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26
Q

What happens to bile from the liver in between meals?

A

It can be redirected to the gallbladder for storage and concentration

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27
Q

What constitutes 50% of the dry weight of bile?

A

bile acids

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28
Q

What are the 4 most important components of bile?

A

bile acids, bile salts, H20, HCO3-

29
Q

What are the primary bile acids?

A

Bile acids formed in the liver

30
Q

2 examples of primary bile acids

A
  • Cholic acid

- Chenodeoxycholic acid

31
Q

What are bile salts?

A

Conjugated bile acids, for example to glycine or taurine (more water soluble)

32
Q

What are the bile acids / salts important for?

A

they are necessary for the formation of micelles due to their amphipathic nature

33
Q

What are other molecules than can be found in the micelles? (2)

A
  • phosphatidyl choline

- cholesterol

34
Q

When do gallstones happen?

A

When one of the constituents of the micelle is overproduced and can’t be integrated, thus forming crystals

35
Q

What is the daily cholesterol balance?

A

input = output = 1.25 g/day

36
Q

What are the 2 inputs of cholesterol?

A
  • Diet (20%)

- Hepatic and extrahepatic synthesis (80%)

37
Q

What are the 2 outputs of cholesterol?

A
  • As cholesterol (75%) to bile

- As bile acids (25%) to bile

38
Q

What are the 2 ways of entry of solutes into bile?

A
  • Active secretion (bile acids, conjugated bilirubin, xenobiotics)
  • Passive permeation (H20, glucose, calcium)
39
Q

What are the 2 important transporters for transport of bile out of the cell?

A
  • BSEP

- MDR (multi drug resistance)

40
Q

What does MDR3 transport?

A

phosphatidyl choline

41
Q

What does MDR1 transport?

A

cationic xenobiotics

42
Q

What does BSEP transport?

A

bile acids

43
Q

What are the 2 ways of transporting water to the bile canaliculi?

A
  • Bile acid dependant flow

- Bile acid independant flow

44
Q

What is bilirubin an end product of?

A

Porphyrin catabolism : hemoglobin - biliverdin - bilirubin

45
Q

What does bilirubin need to be transported to bile?

A

It needs to be conjugated to glucuronic acid in the cell = bilirubin glucuronidase

46
Q

Which cells can modify the bile in the ducts?

A

cholangiocytes, possess a lot of CFTR to attract Cl, H20 and HCO3-

47
Q

What are the 3 factors of bile flow?

A
  • Fluid secretion (cholangiocytes)
  • bile acid dependant flow
  • bile acid independant flow
48
Q

What is the choleretic effect?

A

Aka primary regulation : if bile ACID secretion is higher, then the total bile FLOW will be higher as well

49
Q

What are the 3 ways of regulating bile flow?

A
  • choleretic effect
  • neural regulation
  • secretin
50
Q

What are the 2 neural regulations of bile flow?

A
  • sympathetic : decreases

- parasympathetic : vagus, increases

51
Q

How does secretin regulate bile flow? (3)

A
  • acts on duct cells
  • upregulates CFTR number and function
  • increases bile secretion
52
Q

How is bile secretion compared to the plasma? (2)

A

Isotonic and alkaline

53
Q

How is H20 reabsorbed from the gallbladder?

A

standing gradient osmotic mechanism

54
Q

How much bile is lost per day?

A

0.6 g lost /day (same as daily production)

55
Q

What is the enterohepatic circulation of bile?

A

One bile molecule is reused multiple times

56
Q

How is bile released after a meal?

A

NO and VIP relax the sphincter of odi after activation of the parasympathetic system

57
Q

What is VIP coupled to ?

A

Gs

58
Q

How does Ach help with release of bile after a meal?

A

can constrict the gallbladder by binding to muscarinic 3, 4, 5 receptor

59
Q

What can enhance the effect of Ach on the release of bile? (2)

A
  • CCK (Gq), which is released in response to presence of food.
  • CCK can also activate afferent vagal nerves for the vagovagal reflex
60
Q

How much small intestine mucosa secretion / day?

A

1.5-2L / day

61
Q

What are 4 features of small intestine secretion?

A
  • Isoosmotic
  • Mostly H20
  • Most important electrolyte is HCO3-
  • No production of digestive enzymes
62
Q

What is the main regulation of small intestine secretion

A

mostly parasympathetic, with Ach and VIP : PKA phosphorylates CFTR

63
Q

What is the effect of the cholera toxin?

A

activates all Galpha SU : continuous cAMP signal irreversibly

64
Q

What are the 3 other regulators of small intestine secretion?

A
  • sympathetic system (decrease secretion)
  • ENS : distention of wall, activation of chemoreceptors
  • Paracrine mediators : serotonin (increase fluid secretion)
65
Q

4 properties of colonic secretion

A
  • rich in mucin
  • isotonic
  • no digestive enzymes
  • HCO3- rich
66
Q

How much secretion is presented to the small intestine per day?

A

8.5 L / day

67
Q

How much secretion does the small intestine remove in total / day?

A

6.5 L / day

68
Q

How much secretion does the large intestine remove in total / day?

A

1.9 L / day

69
Q

How much secretion leaves / day in the feces?

A

Around 1L / day

W/Physiology (31 decks)

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