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BRS 11 Gastroenterology > Pancreas > Flashcards

Pancreas Flashcards

1
Q

What does the pancreas originate from?

A

Foregut outgrowth

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2
Q

During the development of the pancreas, which direction does the proximal duodenum rotate?

A

Clockwise

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3
Q

What happens to the dorsal and ventral pancreatic ducts after 11 weeks?

A

They fuse

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4
Q

What is the name of the structure which the bile and pancreatic ducts drain together into?

A

Major papilla

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5
Q

Describe the embryology of the pancreas?

A
  1. Abdominal accessory organs arise as the foregut outgrowths
  2. Proximal duodenum rotates clockwise
  3. Ventral and dorsal pancreatic ducts and buds fuse and form the major papilla
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6
Q

Which major vein runs behind the pancreas?

A

Inferior vena cava and the portal vein

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7
Q

What are the four sections of the pancreas called?

A

Head, neck, body and tail

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8
Q

Where does the head of the pancreas fit into?

A

The circular shape of the duodenum

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9
Q

Which pair of artery and vein runs directly behind the pancreas?

A

Superior mesenteric artery and vein

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10
Q

Which artery runs along the superior border of the pancreas?

A

Splenic artery

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11
Q

What does MRCP do?

A

Magnetic resonance cholangiopancreatography - provides detailed pictures of the hepatobiliary system and pancreas

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12
Q

How do you define Endocrine vs Exocrine secretion?

A

Endocrine = into blood stream to have an effect on a distant target

Exocrine = into the duct to have a direct local effect

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13
Q

Which endocrine hormones does the pancreas secrete?

A
  1. Insullin
  2. Glucagon
  3. Somatostatin
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14
Q

What type of hormone is insulin?

A

An anabolic hormone

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15
Q

What does insulin do?

A

promotes glucose transport into cells & storage as glycogen

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16
Q

Other than glucose uptake into cells, what does insulin promote?

A

promotes protein synthesis & lipogenesis

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17
Q

Which are the main endocrine cells of the pancreas?

A

Islet of Langerhans

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18
Q

What percentage of the gland is responsible for endocrine secretions?

A

2%

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19
Q

What is the main pancreatic exocrine secretion?

A

Pancreatic juice

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20
Q

Where does pancreatic juice get secreted into?

A

Main Pancreatic Duct / Ampulla / Sphincter of Oddi

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21
Q

What are acini?

A

Acini are grape-like clusters of secretory units

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22
Q

What do acinar cells secrete?

A

Acinar cells secrete pro-enzymes into ducts

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23
Q

What are Islets derived from and when do they become islets?

A

Derived from the branching duct system
Become islets when they have completely lost contact with ducts

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24
Q

Where are more islets found in the pancreas?

A

More found in the tail than in the head

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25
Q

What type of secretion do acinar cells partake in?

A

Exocrine (into ducts)

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26
Q

Where are centro acinar cells found?

A

Between acinus and duct

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27
Q

What do the intercellular canaliculi drain into?

A

Drain into pancreatic duct

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28
Q

Which cell type of Islet form 15-20% of the islet tissue?

A

Alpha cells

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29
Q

What do alpha cells secrete?

A

Glucagon

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30
Q

Which islet cell type forms about 60-70% of islet tissue type?

A

Beta cells

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31
Q

What do beta cells secrete?

A

Insulin

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32
Q

What do gamma cells secrete?

A

Somatostatin

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33
Q

What percentage of islet tissue do delta cells take up?

A

5-10%

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34
Q

Which are the more vascularised cell type in the pancreas and why?

A

Islets as this ensures that they have close access to a site for secretion

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35
Q

What are the exocrine pancreatic units (acini) composed of?

A

Secretory acinar cells and duct cells

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36
Q

What do the duct cells of the acini look like?

A

Small and pale

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37
Q

What do the secretory acinar cells of the acini look like?

A

Large with apical secretion granules

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38
Q

What are the two components of the pancreatic juice and what are they made by?

A
  1. Bicarbonate – high volume, watery part made by duct and centroacinar cells
  2. Enzymes – low volume, viscous part made by acinar cells
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39
Q

Which component of the acini secrete the enzyme rich fluid which is viscous and has a low volume?

A

Acinar cells

40
Q

Which component of the acini secrete the bicarbonate rich fluid which is watery and has a high volume?

A

Duct and centroacinar cells

41
Q

What is the concentration of bicarbonate in plasma compared to pancreatic juice?

A

25 mM compared to 120 in pancreatic juice

42
Q

What are the two primary roles of bicarbonate which the pancreas secretes?

A
  1. Neutralise acidic chyme from stomach
  2. Wash low volume enzyme secretion out of the pancreas
43
Q

What are the two benefits of neutralising acidic chyme from the stomach?

A
  1. Prevents damage to duodenal mucosa
  2. Raises pH to optimum range for pancreatic enzymes
44
Q

What happens to bicarbonate secretion when the duodenal pH is less than 5?

A

Linear increase in bicarbonate secretion

45
Q

What happens to bicarbonate secretion when duodenal pH is less than 3?

A

Not much more increase in bicarbonate secretion

46
Q

Why does the rate of HCO3- secretion from the pancreas remain constant when pH is still acidic (less than 3)?

A

No need for pancreatic bicarbonate, as:
1. Bile also contains HCO3- and helps neutralise acid chyme
2. Brunners glands secrete alkaline fluid

47
Q

What enzyme catalyses the reaction between carbon dioxide and water to produce H+ ions and bicarbonate?

A

Carbonic anhydrase

48
Q

In the production of bicarbonate, which substances move through paracellular tight junctions into the lumen of the duct?

A

Na+ and therefore water follows

49
Q

Where does the HCO3- generated from the action of carbonic anhydrase go? And what is it exchanged for?

A

Into the lumen of the pancreatic duct
Exchanged for a Cl- ion

50
Q

Across which membrane in the pancreas does chloride shift occur?

A

Across the apical membrane as bicarbonate is secreted into the duct lumen

51
Q

What maintains the Na+ gradient from high to low across the pancreatic duct cell?

A

Na/K ATPase pumps
Move 3Na into blood for every 2K into the cell
Results in high concentration of Na in blood

52
Q

How does Na+ re-enter the pancreatic duct cell after it has been pumped into the bloodstream by Na/K ATPase?

A

It flows through the Na+/H+ antiporter
Na+ moves into the pancreatic duct cell and H+ (byproduct of reaction between CO2 and H2O) leaves the cell

53
Q

How does K+ return back into the blood after Na/K ATPase pumps it into the cell?

A

Using a K+ Channel

54
Q

How does Cl- return into the lumen after being pumped into the cell through the Cl-/ HCO3- exchanger?

A

CFTR Channel

55
Q

What is the pH of pancreatic venous blood?

A

Acidic due to presence of H+ ions into it

56
Q

What might be the problem for an organ making a cocktail of digestive enzymes?

A

A disease like acute pancreatitis may result in the enzymes digesting the actual organ itself

57
Q

What enzymes are found int the enzyme rich acinar cell secretions?

A

Enzymes for digestion of:
fat (lipases)
protein (proteases)
carbohydrates (amylase)

58
Q

Where are acinar cell enzymes stored and synthesized?

A

→ synthesised & stored in zymogen granules

59
Q

Where are pancreatic enzymes activated?

A

In the duodenum

60
Q

Why are the proteases released as inactive pro-enzymes?

A

protects acini & ducts from auto-digestion

61
Q

What in the duodenum activates pancreatic enzymes?

A

Proteases

62
Q

What activates proteases like trypsinogen?

A

enterokinase - causes trypsinogen to be converted into trypsin which can activate the other pancreatic enzymes

63
Q

What might the blockage of the main pancreatic duct lead to?

A

Might overload protection leading to autodigestion and acute pancreatitis

64
Q

Where is enterokinase secreted from?

A

Duodenal mucosa

65
Q

What is the purpose of enterokinase?

A

Converts trypsinogen into trypsin

66
Q

Is lipase secreted as a precursor or a zymogen?

A

Precursor – secreted in the active form but requires another enzyme to be active

67
Q

What does lipase require in order to be activated and effective?

A

Presence of colipase to be activated and bile salts to be effective

68
Q

In what way are pancreatic enzyme secretions able to adapt?

A

They can adapt to diet

69
Q

What might lack of pancreatic enzymes lead to?

A

Malnutrition even if dietary input is sufficient

70
Q

Why are pancreatic enzymes considered more important than salivary, gastric enzymes?

A

Pancreatic enzymes (+ bile) essential for normal digestion of a meal:

71
Q

Anti-obesity drug Orlistat inhibits pancreatic lipases – what side effects might you expect?

A

Steatorrhoea - increase faecal fat

72
Q

What three situations might you expect to find increased faecal fat, and why?

A

Decreased intestinal fat absorption:

  1. Cystic fibrosis
  2. Chronic pancreatitis
  3. Orlisat
73
Q

What are the three phases of pancreatic juice secretion?

A

Cephalic Phase
Gastric Phase
Intestinal Phase

74
Q

Which phase of pancreatic juice secretion is considered a reflex?

A

Cephalic

75
Q

Describe what happens during the cephalic phase of pancreatic juice secretion?

A

Only enzyme rich, low volume component from acini is released in response to the sight / smell / taste of food

76
Q

Describe what happens during the gastric phase of pancreatic juice secretion?

A

Similar mechanism to cephalic - Stimulation of pancreatic juice secretion from the food arriving in the stomach

77
Q

Describe what happens during the intestinal phase of pancreatic juice secretion?

A

gastric chyme enters duodenum

Both components of the pancreatic juice are secreted into duodenum

78
Q

Which phase of pancreatic juice secretion is hormonally mediated?

A

Intestinal only

79
Q

What controls Pancreatic juice enzyme secretion controlled in acini?

A
  1. Vagus Nerve

2. Cholecystokinin

80
Q

Which cells secrete CCK?

A

I cells

81
Q

What inhibits pancreatic juice enzyme secretion?

A

Gastrin

82
Q

What is Pancreatic juice bicarbonate secretion controlled in duct & centroacinar controlled by?

A

Secretin

83
Q

What neurotransmitter is used to stimulate pancreatic enzyme secretion?

A

ACh via the vagus nerve

84
Q

What stimulates the release of CCK from duodenal I cells?

A

Amino acids and fatty acids in the duodenum

85
Q

What inhibits the release of CCK from I cells?

A

Trypsin

86
Q

What is the osmolarity of acinar fluid?

A

Isotonic

87
Q

What does acinar fluid resemble in terms of concentrations of ions?

A

Plasma concentrations of Na+, K+, Cl− & HCO3− are all similar

88
Q

Why is secretin-stimulated secretion richer in HCO3- than acinar secretion?

A

Because of Cl−/HCO3−exchange

89
Q

what stimulates secretion of H2O & HCO3- from cells lining extralobular ducts?

A

Secretin

90
Q

Describe the Secretin / Bicarbonate negative feedback loop?

A
  1. Luminal pH drops in duodenum
  2. This is detected by the S cells in the duodenum and jejunum
  3. Increases the release of secretin
  4. This increases bicarbonate secretion which raises the pH
91
Q

What effect does CCK alone have on bicarbonate secretion?

A

None

92
Q

How can bicarbonate secretion be increased?

A

Having CCK and Secretin stimulus

93
Q

Does the vagus nerve have any impact on bicarbonate secretion alone?

A

No

94
Q

Does secretin have any affect on enzyme secretion?

A

No

95
Q

Describe the summary of a meal?

A
  1. Food mixed and digested in stomach at pH 2
  2. Chyme moves into duodenum
  3. This chyme is acidic and pH drops
  4. This causes more secretin from S cells to be released, increasing pancreatic juice secretion
  5. Combination of pancreatic juice, bile and Brunner’s gland secretions increases pH to neutral/alkaline
  6. Peptides and fat in duodenum cause sharp increase in CCK and vagal nerve stimulation, stimulating pancreatic enzyme release
  7. Increase peaks by 40 mins and continues until stomach is empty
  8. CCK potentiates the effects of secretin
96
Q

At what point does CCK and Vagus Nerve Stimulation peak after a meal?

A

By 30 minutes, continues until stomach empties

97
Q

Why is CCK needed to potentiate the effect of secretin on aqueous component?

A

Most of duodenum is not at a low pH

BRS 11 Gastroenterology (25 decks)

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