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Y1 Alimentary > Pancreas > Flashcards

Pancreas Flashcards

1
Q

Where does the pancreas develop from?

A

Foregut derivative arising at the foregut-midgut juntion. Dorsal and ventral buds, ventral bud is part of hepatobiliary bud

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2
Q

How is the pancreas subdivided?

A

Head, neck, body, tail and uncinate (latin for hook like) process

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3
Q

Where is islet tissue most abundant?

A

Tail

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4
Q

What are the main posterior relations to the pancreas?

A

IV, abdominal aorta and left kidney

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5
Q

What arteries have close relations with and supply the pancreas?

A

Coeliac and superior mesenteric arteries

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6
Q

Define endocrine?

A

Secretion into blood stream to have an effect on distant target organs (autocrine/paracrine) - ductless glands

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7
Q

Define exocrine?

A

Secretion into a duct to have a direct local effect

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8
Q

What are the main endocrine secretions of the pancreas?

A

Insulin, glucagon, somatostatin

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9
Q

What does insulin do?

A

Anabolic hormone that promotes glucose transport into cells and storage as glycogen. Reduces blood glucose, promotes protein synthesis and lipogenesis

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10
Q

What does glucagon do?

A

Increase gluconeogenesis and glycogenolysis (to increase blood glucose)

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11
Q

What does somatostatin do?

A

Endocrine cyanide

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12
Q

What is the endocrine part of the pancreas? What percentage of the pancreas is it?

A

Islets of langerhans. 2%

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13
Q

What does the endocrine part of the pancreas do?

A

Secretes hormones into blood - insulin and glucagon and regulates blood glucose, metabolism and growth effects

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14
Q

What does the exocrine part of the pancreas do?

A

Secretes pancreatic juice into duodenum via pancreatic duct/common bile duct
Digestive function

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15
Q

What percentage of the pancreas does exocrine actions?

A

98%

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16
Q

What kinds of pancreatic cells are involved in exocrine action?

A

Ducts and acini

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17
Q

What do acini look like?

A

Grape like clusters of secretory units

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18
Q

What do acinar cells secrete?

A

Pro-enzymes into ducts

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19
Q

What do endocrine cells become in pancreas?

A

Alpha and beta islets of langerhans

More in tails than head

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20
Q

Where do the endocrine pancreatic cells derive from?

A

Branching duct system

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21
Q

What are the composition of islets of langerhans (how much of there of each type of cell)

A

15-20% alpha cells
60-70% beta cells
5-10% delta cells

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22
Q

What do delta cells produce in islets of langerhans?

A

Somatostatin

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23
Q

Why must the islets of langerhans be highly vascular?

A

Ensure all endocrine cells have close access to a site for secretion

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24
Q

What are the two components of pancreatic juice?

A

Low volume of viscous, enzyme rich acinar cells

High volume of HCO3 rich duct and centroacinar cells

25
Q

What is the point of the bicarbonate secretion in the pancreas?

A

Neutralises acid chyme from the stomach, preventing damage to duodenal mucosa and raises pH to optimum range for pancreatic enzymes to work

26
Q

Where is the bicarbonate secreted from in the pancreas?

A

Duct and centroacinar cells

27
Q

What else does the bicarb solution in the pancreas do other than neutralise?

A

Washes low vol enzyme secretion out of pancreas and into the duodenum

28
Q

When does the pancreas secrete more bicarb?

A

When the pH is less than 5 but at less than 3 there is not much more increase in bicarb rate

29
Q

Why does the bicarb secretion stop when the pH is still acid?

A

Bile also contains bicarb and helps neutralise the acid chyme in liver and brunners glands also secrete alkaline fluid in small intestine

30
Q

What is the mechanism of bicarbonate secretion?

A
  1. Seperation H+ and HCO3- by carbonic anhydrase. Na+ down gradient via paracellular tight junctions and H2O follows
  2. exchange of Cl/HCO3 (lumen) and Na/H (basolateral memb) driven by electrochemical gradients
  3. Na gradient maintained using Na/K pump - atp primary active transport
  4. K returns to blood - K channel and Cl returns to lumen via Cl channel
31
Q

What are zymogens

A

Pro-enzymes

32
Q

Why are acinar cell enzymes secreted?

A

For digestion of fat (lipases), protein (proteases) and carbs (amylase)

33
Q

Where are acinar cell enzyme secretions synthesised and stored?

A

In zymogen granules

34
Q

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

A

????????

35
Q

What are proteases released as in pancreas? Why?

A

Inactive proenzymes

Protects acini and ducts from autodigestion

36
Q

Where do the acinar cell enzyme secretion enzymes become activated?

A

Duodenum

37
Q

What can a blockage of pancreatic duct do?

A

Overload protection and result in autodigestion = acute pancreatitis

38
Q

What does the pancreas contain to prevent trypsin activation?

A

Trypsin inhibitor

39
Q

Where does the enterokinases cleave the trypsinogen?

A

Between valine and isoleucine

40
Q

What starts protein digestion?

A

Pepsin in the stomach in acid conditions

41
Q

What happens when chyme enters duodenum from stomach?

A

Pepsin mixed into it, but is soon inactivated as alkaline conditions

42
Q

What enzyme is secreted from what to convert typsinogen to trypsin?

A

Duodenal mucosa secretes an enzyme - enterokinase (enteropeptidase)

43
Q

What does trypsin do?

A

Converts all other proteolytic and some lipolytic enzymes

44
Q

What is special about lipase?

A

Lipase is secreted in active form but requires colipase which is secreted as a precursor

45
Q

What is an anti obesity drug that inhibits pancreatic lipases?

A

Orlistat

hense reduce intestinal fat absorption

46
Q

What are side effects to orlistat?

A

A pancreatic lipase inhibitor cauess:

Steatorrhoea

47
Q

When does steatorrhea occur?

A

When pancreatic lipase secretion is significantly reduced eg in CF, chronic pancreatitis, orlistat

48
Q

How is pancreatic secretion regulated? What nerve and what does it do?

A

Vagus nerve
Cholinergic
Communicates info from gut to brain

49
Q

What happens in the 3 stages of food digestion but in the pancreas?

A
  1. cephalic phase - enzyme rich component only. Low vol - mobilises enzymes
  2. stimulation of pancreatic secretion, same mech as cephalic
  3. hormone mediated, gastric chyme enter duodenum and both components of pancreatic juice stimulated - enzymes and HCO3
50
Q

How is bicarbonate secretion controlled in pancreas?

A

Release of hormone Secretin (cAMP)

51
Q

How is enzyme secretion controlled in pancreas?

A

Vagal reflex and

Hormone - cholecystokinin (CCK) (Ca2+/PLC) - CCK also stimulate bile secretion

52
Q

How is CCK switched off in pancreas?

A

Cephalic phase ends when meal eaten, absorption of fats and peptides removes local luminal stimulus for CK release from mucosa

53
Q

What effect does CCK alone have on bicarbonate secretion in pancreas?

A

no effect

54
Q

What effect does CCK and secretin together have on bicarb secretion in pancreas?

A

Markedly increase bicarb release

55
Q

What effect does vagus nerve have on bicarb secretion in pancreas?

A

Similar lack of effect as CCK

56
Q

What effect does secretin have on enzyme secretion in pancreas?

A

NO EFFECT

57
Q

What stimulates release of secretin in pancreas?

A

H+ ions in duodenum stimulate realse, and also stimulate release of pancreatic juice to raise the pH

58
Q

What causes a sharp CCK rise in pancreas

A

Peptides and fat in duodenum

Y1 Alimentary (21 decks)

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