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pancreas Flashcards

1
Q
  • What happens in the development of the pancreas, afer 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 is the uncinate process of the pancreas originated from?
  • What do the ventral and dorsal ducts emerge as respectively?
A

Ventral bud and duct

Ventral - Main pancreatic duct at the major papilla
Dorsal - Accessory pancreatic duct at the minor papilla
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3
Q
  • Is the accessory pancreatic duct present in everyone?

- What 2 ducts join at the major papilla?

A

No, in most adults it has been degenerated

Main pancreatic duct  common Bile duct
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4
Q
  • What does the fact the the pancreas is a retoperitoneal structure mean?
A

It does not exist within the abdomen

It is behind the posterior to the peritoneum
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5
Q
  • Which vein is formed by the joinng of the splenic vein and the superior mesenteric vein?
A

Portal vein

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6
Q
  • What is MRCP used for and how does it work?
A

Procedure can be used to determine whether gallstones are lodged in any of the ducts surrounding the gallbladder

Uses magnetic resonance imaging to visualise the biliary and pancreatic ducts non-invasively
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7
Q
  • What is pancreas divisum and why does it cause the patient to have recurrent episodes of pancreatitis?
A

Ventral bud and dorsal buds fail to fuse and 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 pancreatits
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8
Q
  • What type of imaging is used when a patient is bleeding internally and how is it done?
A

Angiography - accessing femoral artery, put needle in and thread wire via femoral artery to aorta. Then put dye into the coeliac axis

When patients are bleeding
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9
Q
  • How do you define Endocrine vs 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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10
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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11
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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12
Q
  • Describe the structure of acini in the pancreas

- What do acini secrete into ducts?

A

Attached to ducts
Grape-like clusters of secretory units

Pro-enzymes
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13
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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14
Q
  • Are there more islets in the head or the tail of the pancreas?
A

Tail

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15
Q
  • Are the islets poorly or highly vasculated?

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

A

Highly, so it has a very good blood supply
Ensures that all endocrine cells have a site for close access to a site for secretion

alpha = 15-20%
beta = 60-70%
gamma = 5-10%
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16
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
17
Q
  • Describe the components of pancreatic juice formed by the Acinar cells
  • Describe the other components of pancreatic juice formed by the Duct and Centroacinar cells
A

Low volume, Viscous, Enzyme-rich

High volume, Watery, HCO3- rich

18
Q
  • What are the functions of the bicarbonate secretion in the pancreatic juice?
A

Neutralises acid chyme from stomach

Prevents damage to duodenal mucosa

Raises pH to optimum range for pancreatic enzymes to work

Washes low volume enzyme secretion out of pancreas into duodenum
19
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
20
Q
  • Describe how HCO3- is produced and secreted by the pancreatic duct cells
A

CO2 enters pancreatic duct cell from blood and catalysed by carbonic anhydrase it reacts with H20 to form H+ and HCO3-

Na+ moves down gradient via paracellular junctions and H20 follows from the blood to the lumen

AE1 transporter exchanges HCO3- from 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+ concn. gradient in the cell, Na+/K+ATPase transports Na+ into blood and K+ into cell

To maintain K+ concn. gradient in cell, K+ returns to blood via K+ channels

Cl- returns to lumen via Cl- channel (CFTR) to maintain concn. gradient established by AE1 transporter
21
Q
  • What makes gastric venous blood alkaline and pancreatic venous blood acidic?
A

Stomach- H+ → Gastric Juice, HCO3- → blood

Pancreas- HCO3- secreted as pancreatic juice, H+ → blood
22
Q
  • Which classes of digestive enzymes are present in the Acinar cell enzyme secretion?
  • Why are proteases released as inactive pro-enzymes and what are they stored in?
  • what would happen if there was a blockage in MPD?
A

Lipases - Fat
Proteases - Protein
Amylase - Carbohydrates

Protects acini and ducts from auto-digestion, zymogen granules

may overload protection-> auto digestion

23
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

24
Q
  • What enzyme is secreted by the duodenal mucosa and what does it do?
  • What is the function of trypsin?
A

Enterokinase (enteropeptidase)
Converts trypsinogen → trypsin

Converts all other proteolytic and some lipolytic enzymes into their active form
25
Q
  • Why is it not dangerous to secrete lipase in its active form?
  • What can a lack of pancreatic enzymes lead to?
A

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

Malnourishment
26
Q
  • Describe how the cephalic phase is involved in the control of pancreatic juice secretion?
A

Reflex response to sight/smell/taste of food

Enzyme-rich component only

Low volume - 'mobilises' enzymes
27
Q
  • Describe how the gastric phase is involved in the control of pancreatic juice secretion?
A

Stimulation of pancreatic secretion originating from food arriving in the stomach

Same mechanisms involved as for cephalic phase
28
Q
  • Describe how the intestinal phase is involved in the control of pancreatic juice secretion?
A

Hormonally mediated when gastric chyme enters duodenum

Both components of pancreatic juice stimulated enzymes & HCO3- juice flows into duodenum
29
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)
30
Q
  • What hormone controls the pancreatic juice bicarbonate secretion in the duct and centroacinar cells?
  • What compounds stimulate the release of CCK from the duodenal I cells?
A

Secretin (cAMP)

Amino Acids and Fatty Acids
31
Q
  • What effect does trypsin have on the release of CCK from duodenal I cells?
  • Is acinar fluid isotonic?
A

Inhibitory

Yes and it resembles plasma in its concentrations of Na+, K+, Cl- and HCO3-
32
Q
  • Why is secretin-stimulated secretion richer in HCO3- than acinar secretion?
A

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

As it flows down into the larger pancreatic ducts, it becomes richer in HCO3- due to there being more duct and centroacinar cells
33
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-
34
Q
  • Does CCK alone have any effect on HCO3- secretion?
  • When does CCK have an effect on HCO3- secretion?
  • What effect does secretin have on enzyme secretion?
  • What effect does bile and Bruner’s gland secretions have on the pH?
A

no

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

none

Increase pH

35
Q

summarise what happens when a meal has been eaten

A

food is mixed and digested in stomach at a Ph of 2

H+ ions detected in duodenum, inc secretin and increased pancreatic juice
increased bile and Brunner gland secretions

peptides and fats in duodenum cause a sharp increase in CCK and vagal nerve stimulation, stimulates pancreatic enzyme release

CCK potentiates effects of secretin on aqueous component, needed as most of duodenum not at low enough PH

BRS (41 decks)

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