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BRS Gastroenterology > Pancreas > Flashcards

Pancreas Flashcards

1
Q

What happens in the development of the pancreas, after the proximal duodenum rotates clockwise?

A

Ventral and dorsal pancreatic buds and ducts fuse.

Bile and pancreatic ducts join to drain together at major papilla.

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2
Q

What does the uncinate process of the pancreas originate from?

A

Ventral bud and duct

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3
Q

What do the ventral and dorsal ducts emerge as respectively?

A

Ventral - MPD at the major papilla

Dorsal - APD at the minor papilla

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4
Q

Is the accessory pancreatic duct present in everyone?

A

No, in most adults it has been degenerated

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5
Q

What 2 ducts join at the major papilla?

A

MPD and CBD

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6
Q

What does the fact the the pancreas is a retroperitoneal structure mean?

A

It doesn’t exist within the abdomen.

It’s behind the posterior peritoneum.

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7
Q

What structures sits in front of the pancreas?

A

Transverse colon and stomach

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8
Q

Which vein is formed by the joining of the splenic vein and the superior mesenteric vein?

A

Portal vein

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9
Q

Is the accessory pancreatic duct visible in MRCP?

A

No

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10
Q

What is pancreas divisum and why does it cause the patient to have recurrent episodes of pancreatitis?

A

Ventral and dorsal buds fail to fuse so the ventral duct, which usually has a large enough capacity to cope with the flow of the pancreatic juice can no longer do so. The large flow has to therefore go through a minor duct and so they get recurrent episodes of pancreatitis.

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11
Q

What is the most useful method of imaging for the pancreas?

A

CT Scan

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12
Q

Define endocrine and exocrine secretion.

A

Endocrine: Secretion into the blood stream to have effect on distant target organ (Autocrine/Paracrine) - Ductless glands

Exocrine: Secretion into a duct to have direct local effect

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13
Q

What are the main endocrine secretions of the pancreas and their actions?

A

Insulin:
Anabolic hormone
Promotes glucose transport into cells and storage as glycogen
Decreased blood glucose
Promotes protein synthesis and lipogenesis

Glucagon:
Increases gluconeogenesis and glycogenolysis
Increases blood glucose

Somatostatin - Inhibits everything - “Endocrine cyanide”

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14
Q

What percentage of the pancreatic secretion is endocrine and what part of the pancreas does this?

A

2%

Islets of Langerhans

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15
Q

What hormones do the IoH secrete?

A

Insulin, glucagon and somatostatin

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16
Q

What percentage of the pancreatic secretion is exocrine and what does this involve?

A

98%

Secretion of pancreatic juice into duodenum via MPD/sphincter of Oddi/ampulla.

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17
Q

Describe the structure of acini in the pancreas.

A

Attached to ducts.

Grape-like clusters of secretory units.

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18
Q

What do acini secrete into ducts?

A

Pro-enzymes

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19
Q

Describe the structure of islets.

A

Derived from branching duct system but lose contact with the ducts to become islets. Differentiate into alpha and beta cells secreting into the blood.

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20
Q

Are there more islets in the head or the tail of the pancreas?

A

Tail

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21
Q

Are the islets poorly or highly vasculated?

A

Highly

Ensures thast all endocrine cells have a site for close access to a site for secretion.

22
Q

How much of the islets are composed of alpha, beta and delta cells respectively?

A 
alpha = 15-20% - glucagon 
beta = 60-70% - insulin 
delta = 5-10% - somatostatin
23
Q

Compare the structures of the secretory acinar cells and the duct cells in the acini of the pancreas.

A

Secretory acinar cells - Large with apical secretions

Duct cells - Small and pale

24
Q

Compare the 2 components of pancreatic juice formed by the Duct and Centroacinar cells, and the acinar cells.

A

Duct and centroacinar cells - High volume, watery, HCO3- rich

Acinar cells - Low volume, viscous, enzyme-rich

25
Q

What cells in the pancreas secrete HCO3-?

A

Duct and centroacinar cells

26
Q

What are the functions of the bicarbonate secretion in the pancreatic juice?

A

Neutralises acid chyme from stomach by:

  • preventing damage to duodenal mucosa.
  • raising pH to optimum range for pancreatic enzymes to work.

Washes low volume enzyme secretion out of pancreas into duodenum.

27
Q

How does HCO3- affect the pH of pancreatic juice?

A

Increases

pH of pancreatic juice - 7.5-8.0.

28
Q

Why does HCO3- secretion stop increasing when pH goes below 3?

A

Bile also contains HCO3- and helps neutralise acid chyme.

Brunners glands secrete alkaline fluid.

29
Q

Outline the effect of duodenal pH on bicarbonate secretion.

A

Duodenal pH <5 - linear increase in pancreatic HCO3- secretion, but when duodenal pH <3 there’s not much more increase in HCO3- secretion.

30
Q

Describe how HCO3- is produced and secreted by the pancreatic duct cells.

A

CO2 enters blood and, catalysed by carbonic anhydrase, it reacts with H20 to form H+ and HCO3-. Simultaneously, Na+ moves down its concentration gradient via paracellular junctions and H20 follows from the blood to the lumen.
AE1 transporter exchanges HCO3- from pancreatic duct cell into lumen with Cl- into the duct cell.
Na+/H+ antiporter active on the basolateral membrane and Na+ enters the cell down gradient.
To maintain Na+ concentration gradient in the cell, Na+/K+ATPase transports Na+ into blood and K+ into cell - using ATP (Primary AT).
To maintain K+ concentration gradient in cell, K+ returns to blood via K+ channels.
Cl- returns to lumen via Cl- channel (CFTR) to maintain concentration gradient established by AE1 transporter.

31
Q

Compare the pH of gastric and pancreatic venous blood.

A

GVB - Alkaline (gastric juice is acidic)

PVB - Acidic (pancreatic juice is alkaline)

32
Q

What makes gastric venous blood alkaline and pancreatic venous blood acidic?

A

Stomach
H+ → Gastric Juice
HCO3- → blood

Pancreas
HCO3- secreted → juice
H+ → blood

33
Q

Which classes of digestive enzymes are present in the Acinar cell enzyme secretion?

A

Lipases - Fat
Proteases - Protein
Amylase - Carbohydrates

34
Q

Why are proteases released as inactive pro-enzymes?

A

Protects acini and ducts from auto-digestion.

35
Q

What other protective mechanisms against auto-digestion of the pancreas are there?

A

Pancreas contains trypsin inhibitor to prevent trypsin activation.
Enzymes only activated in the duodenum - where they have to start digesting food.

36
Q

What enzyme is secreted by the duodenal mucosa and what does it do?

A

Enterokinase (enteropeptidase)

Converts trypsinogen → trypsin

37
Q

What is the function of trypsin?

A

Converts all other proteolytic and some lipolytic enzymes in to their active form.

38
Q

Why is it not dangerous to secrete lipase in its active form?

A

Requires colipase for action and the presence of bile salts for effective action.

39
Q

What can a lack of pancreatic enzymes lead to?

A

Malnourishment

40
Q

What is a side effect you might expect from anti-obesity drug Orlistat which inhibits pancreatic lipases?

A

Steatorrhoea

41
Q

Describe the 3 phases involved in the control of pancreatic juice secretion?

A

Cephalic phase:
Reflex response to sight/smell/taste of food.
Enzyme-rich component only.
Low volume - ‘mobilises’ enzymes.

Gastric phase:
Stimulation of pancreatic secretion originating from food arriving in the stomach.
Same mechanisms involved as for cephalic phase.

Intestinal phase:
Hormonally mediated when gastric chyme enters duodenum.
Both components of pancreatic juice stimulated enzymes & HCO3- juice flows into duodenum.

42
Q

What 2 components is the pancreatic juice enzyme secretion controlled in the acini by?

A

Vagus nerve - Cholinergic; vagal stimulation of enzyme secretion (& communicates info from gut to brain)

Cholecystokinin (CCK) (Ca2+/PLC)

43
Q

What hormone controls the pancreatic juice bicarbonate secretion in the duct and centroacinar cells?

A

Secretin (cAMP)

44
Q

What compounds stimulate the release of CCK from the duodenal I cells?

A

AAs and FAs

45
Q

What effect does trypsin have on the release of CCK from duodenal I cells?

A

Inhibitory

46
Q

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

A

Because of the HCO3-/Cl- exchange in the extralobular duct.

As it flows down into the larger pancreatic ducts, it becomes richer in HCO3-.

47
Q

Describe the negative feedback loop involved in the control of HCO3- secretion in ducts?

A

Decrease in pH in duodenum activates S cells to release Secretin.
Secretin stimulates pancreatic ductal HCO3- secretion which increases pH.
Since pH is increased, the S cells cannot be stimulated to release more secretin, controlling the secretion of HCO3-.

48
Q

Does CCK alone have any effect on HCO3- secretion?

A

No

49
Q

When does CCK have an effect on HCO3- secretion?

A

It markedly increases HCO3- secretion that has been stimulated by secretin.

50
Q

What effect does secretin have on enzyme secretion?

A

None

51
Q

What effect does bile and Bruner’s gland secretions have on the pH?

A

Increase pH

BRS Gastroenterology (11 decks)

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