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GASTROENTEROLOGY > Pancreas > Flashcards

Pancreas Flashcards

1
Q

What does the pancreas originate from?

A

Foregut outgrowths

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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 ducts 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 - once they have completely lost contact with ducts = islets

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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 - indo 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 - 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

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?

A
  1. Bicarbonate

2. Pancreatic enzymes

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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 hhe 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. Washes low volume enzyme secretion out pancreas

43
Q

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

A

prevents damage to duodenal mucosa

Raises pH to optimum range for pancreatic enzymes to work

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 remain constant when pH is still acid (pH less than 3?

A

No need for pancreatic bicarbonate -

  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 - bicarbonate is secreted into the duct

51
Q

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

A

The presence of Na+/K+ ATPase Pumps - pumps 3 x Na+ into blood for every 2 K+ into the cell therefre resulting in a high concentration of Na+ outside the cell in the blood

52
Q

How does Na+ reenter the pancreatic duct cell after it has been pumped up by Na/K+ ATPase?

A

It flows through an antiporter - Na+/H+ antiporter with Na+ going into the pancreatic duct cell and H+ (which as produced as a byproduct of water and CO2 reaction) 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 blood after being pumped into the cell through the Cl-/ HCO3- exchanged?

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

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 byt 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

Presence of bile salts in order 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 affect 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

Secretin has NO EFFECT on enzyme secretion

95
Q

Describe the summary of a meal?

A
  1. Food mixed, digested in stomach, pH 2
  2. Chyme into duodenum
  3. This chyme is acidic and therefore pH drops
  4. This causes more Secretin from S cells to be released - increased pancreatic juice secretion + bile & Brunner’s gland secretions
  5. Peptides & fat in duodenum cause sharp ↑ in CCK & vagal nerve stimulation
  6. CCK potentiates the effects of secretin
96
Q

At what point does CCK and Vagal 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 not at ↓pH

GASTROENTEROLOGY (25 decks)

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