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BRS > The pancreas > Flashcards

The pancreas Flashcards

1
Q

What are the steps of pancreatic embryology?

A
  1. Abdominal accessory organs arise as foregut outgrowths: liver bud, gallbladder, ventral pancreatic bud and duct, dorsal pancreatic bud and duct
    2.Proximal duodenum rotates clockwise- takes 11 weeks
  2. 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

How is the duodenum arranged?

A

Divided into D1, D2, D3, D4

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3
Q

What is the right colic flexure also known as?

A

hepatic flexure (bend in colon)

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4
Q

What is the left colic flexure also known as?

A

splenic flexure (bend in colon)

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5
Q

What is a method of imaging the pancreas

A

MRCP- Magnetic Resonance cholangiopancreatography

Angiography- for bleeding- put a needle into the femoral artery to the aorta

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6
Q

What is pancreatic division?

A

Main pancreatic duct and ventral duct do not fuse together

Patients with this will get recurrent pancreatitis

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7
Q

What is endocrine secretion?

A

Secretion into blood stream to have effect on distant target organ (autocrine/paracrine)- ductless glands (2% of secretion)

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8
Q

What is exocrine secretion?

A

Secretion into a duct to have direct local effect (98% of secretion)

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9
Q

What are the main endocrine secretions of the pancreas?

A

Insulin, glucagon and somatostatin

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10
Q

What is the role of insulin?

A

Anabolic hormone
Promotes glucose transport into cells and storage as glycogen
decreases blood glucose levels
promotes protein synthesis and lipogenesis

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11
Q

What is the role of glucagon?

A

Increased gluconeogenesis and glycogenolysis

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12
Q

What’s the role of somatostatin?

A

“endocrine cyanide”

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13
Q

What cells carry out endocrine secretion?

A

Islets of langerhans
Secrete hormones into blood- insulin, glucagon, somatostatin, pancreatic polypeptide
Regulate glucose, metabolism and grown effects

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14
Q

What is the role of exocrine secretion of the pancreas?

A

Secretes pancreatic juice into duodenum via main pancreatic duct /sphincter of oddi/ampulla
Has digestive function

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15
Q

What cells are found in the pancreas

A

Acini:

  • ducts
  • grape like clusters of secretory units
  • acinar cells secrete proenzymes into ducts

Islets:

  • derived from branching duct system
  • lose contact with ducts- become islets
  • differentiate into alpha and beta cells secreting into blood
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16
Q

How are islets composed?

A

Alpha cells: form about 15-20% of islet tissue and secrete glucagon
Beta cells: form about 60-70% of islet tissue and secrete insulin
delta cells: form about 5-10% of islet tissue and secrete somatostatin
Acini: islets are highly vascular ensuring that all endocrine cells have close access to site for secretion

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17
Q

What is the role of exocrine secretion of the pancreas?

A

Secretes pancreatic juice into duodenum via main pancreatic duct /sphincter of oddi/ampulla
Has digestive function

18
Q

What cells are found in the pancreas

A

Acini:

  • ducts
  • grape like clusters of secretory units
  • acinar cells secrete proenzymes into ducts

Islets:

  • derived from branching duct system
  • lose contact with ducts- become islets
  • differentiate into alpha and beta cells secreting into blood
19
Q

How are islets composed?

A

Alpha cells: form about 15-20% of islet tissue and secrete glucagon
Beta cells: form about 60-70% of islet tissue and secrete insulin
delta cells: form about 5-10% of islet tissue and secrete somatostatin

20
Q

How are exocrine acini composed?

A

Exocrine pancreatic units
Have secretory acinar cells: large with apical secretion granules
Duct cells: small and pale

21
Q

What is pancreatic juice made up out of?

A

Acinar cells secrete low volume, viscous, enzyme-rich pancreatic juice
Duct and centroacinar cells secrete high volume, watery, HCO3- rich pancreatic juice

22
Q

How is bicarbonate secreted?

A

Secreted by duct and centroacinar cells
Pancreatic juice is high in bicarbonate- 120mM with a pH of 7.5- 8.0
It neutralizes chyme from stomach which prevents damage to duodenal mucosa and raises pH to optimum range for digestive enzymes
It washes low volume enzyme secretion out of pancreas into duodenum

23
Q

How does duodenal pH effect HCO3- secretion rate?

A

Duodenal pH is <5 there is a linear increase in pancreatic HCO3- secretion
If duodenal secretion is <3 there isn’t as much of an increase in HCO3- secretion
The reason this happens is because bile salts contain HCO3- and also help neutralise chyme
Brunners glands also secrete alkaline fluid

24
Q

What is the mechanism of pancreatic HCO3- secretion

A

1.Separation of H+ and HCO3- by carbonic anhydrase
Na+ moves down conc. gradient via paracellular tight junctions and H2O follows

  1. Cl-/HCO3- exchange at lumen. Na+/H+ exchange at basolateral membrane into bloodstream (by Na/H exchanger type 1- NHE1)- this is driven by an electrochemical gradient (High extracellular Na and Cl-)
  2. Na+ gradient into cell from blood maintained by Na+/K+ exchange pump. Uses ATP- primary active transport
  3. K+ returns to blood via K+ channel. Cl- returns to lumen via Cl- channel (cystic fibrosis transmembrane conductance regulator CFTR)
25
Q

What happens overall in bicarbonate secretion?

A

Stomach:

  • H+ goes into gastric juice
  • HCO3- goes into blood
  • Gastric venous blood is alkaline

Pancreas:
- HCO3- secretes into juice
-H+ secreted into blood
Pancreatic venous blood is acidic

26
Q

What enzymes do acinar cells secrete?

A

Lipases, proteases and amylase
Proteases are released as inactive proenzymes (zymogen)- Protects acini and ducts from autodigestion
Pancreas also contains a trypsin inhibitor to prevent trypsin activation
Enzymes are activated in the duodenum
Blockage of main pancreatic duct may overload protection and cause autodigestion

27
Q

How is lipase secreted?

A

Secreted in active form however requires colipase which binds to fat globules
Lipases require the presence of bile salts for effective action

28
Q

How are pancreatic enzyme secretions modified?

A

They adapt to diet

Lack of pancreatic enzymes and bile can lead to malnutrition

29
Q

What drug inhibits pancreatic lipases and what side effects does it have?

A

Orlistat
Leads to increases faecal fat
Occurs when pancreatic lipase secretion is reduced
Can be used for CF or chronic pancreatitis

30
Q

What are the 3 phases that control pancreatic juice secretion?

A

Cephalic, gastric and intestinal phase

31
Q

What controls pancreatic juice secretion in acini?

A

Enzyme secretion controlled by:

  1. Vagus nerve:
    - cholinergic
    - vagal stimulation and enzyme secretion
  2. Cholecystokinin (CCK)
32
Q

What happens in the gastric phase?

A

Stimulation of pancreatic secretion originating from food arriving in the stomach
Same mechanisms as in cephalic phase

33
Q

What happens in the intestinal phase?

A

70-80% of pancreatic secretion
Hormonally mediated when gastric chyme enters duodenum
Both components of pancreatic juice stimulated
Enzymes and HCO3- juice flows into duodenum

34
Q

What controls pancreatic juice secretion in acini?

A

Enzyme secretion controlled by:

  1. Vagus nerve:
    - cholinergic
    - vagal stimulation and enzyme secretion
  2. Cholecystokinin (CCK)
35
Q

What controls pancreatic juice secretion in duct and centroacinar cells?

A

Bicarbonate secretion controlled by:

Secretin (cAMP)

36
Q

How does the vagus nerve control enzyme secretion in acinar cells

A

Acetylcholine is the NT

37
Q

What mechanisms are responsible for controlling release of CCK?

A 
Released from duodenal I cells
Stimulatory effects
Inhibitory effects
CCK- releasing peptide (CCK-RP)
Gastrin releasing peptide (GRP)
38
Q

Can CCK work alone?

A

CCK alone has no effect on HCO3- secretion
It needs secretin
Secretin has no effect on enzyme secretion
Vagus nerve has similar effect to CCK

39
Q

How would you summarise secretions in response to a meal?

A

H+ ions in duodenum -> increase in secretin -> increase in pancreatic juice -> increase in pH (+bile and brunner’s gland)

Peptides and fats in duodenum->increase in CCK and vagal stimulation -> pancreatic enzyme release

40
Q

How is HCO3- secretion controlled in ducts?

A

Low duodenal pH stimulates s cells to secrete secretin which stimulate pancreatic HCO3- secretion which raises the pH

41
Q

Can CCK work alone?

A

CCK alone has no effect on HCO3- secretion
It needs secretin
Secretin has no effect on enzyme secretion

42
Q

How would you summarise secretions in response to a meal?

A

H+ ions in duodenum -> increase in secretin -> increase in pancreatic juice -> increase in pH (+bile and brunners gland)

Peptides and fats in duodenum->increase in CCK and vagal stimulation -> pancreatic enzyme release

BRS (60 decks)

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