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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
What cells in the pancreas secrete HCO3-?
Duct and centroacinar cells
26
What are the functions of the bicarbonate secretion in the pancreatic juice?
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
How does HCO3- affect the pH of pancreatic juice?
Increases | pH of pancreatic juice - 7.5-8.0.
28
Why does HCO3- secretion stop increasing when pH goes below 3?
Bile also contains HCO3- and helps neutralise acid chyme. | Brunners glands secrete alkaline fluid.
29
Outline the effect of duodenal pH on bicarbonate secretion.
Duodenal pH <5 - linear increase in pancreatic HCO3- secretion, but when duodenal pH <3 there's not much more increase in HCO3- secretion.
30
Describe how HCO3- is produced and secreted by the pancreatic duct cells.
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
Compare the pH of gastric and pancreatic venous blood.
GVB - Alkaline (gastric juice is acidic) PVB - Acidic (pancreatic juice is alkaline)
32
What makes gastric venous blood alkaline and pancreatic venous blood acidic?
Stomach H+ → Gastric Juice HCO3- → blood Pancreas HCO3- secreted → juice H+ → blood
33
Which classes of digestive enzymes are present in the Acinar cell enzyme secretion?
Lipases - Fat Proteases - Protein Amylase - Carbohydrates
34
Why are proteases released as inactive pro-enzymes?
Protects acini and ducts from auto-digestion.
35
What other protective mechanisms against auto-digestion of the pancreas are there?
Pancreas contains trypsin inhibitor to prevent trypsin activation. Enzymes only activated in the duodenum - where they have to start digesting food.
36
What enzyme is secreted by the duodenal mucosa and what does it do?
Enterokinase (enteropeptidase) | Converts trypsinogen → trypsin
37
What is the function of trypsin?
Converts all other proteolytic and some lipolytic enzymes in to their active form.
38
Why is it not dangerous to secrete lipase in its active form?
Requires colipase for action and the presence of bile salts for effective action.
39
What can a lack of pancreatic enzymes lead to?
Malnourishment
40
What is a side effect you might expect from anti-obesity drug Orlistat which inhibits pancreatic lipases?
Steatorrhoea
41
Describe the 3 phases involved in the control of pancreatic juice secretion?
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
What 2 components is the pancreatic juice enzyme secretion controlled in the acini by?
Vagus nerve - Cholinergic; vagal stimulation of enzyme secretion (& communicates info from gut to brain) Cholecystokinin (CCK) (Ca2+/PLC)
43
What hormone controls the pancreatic juice bicarbonate secretion in the duct and centroacinar cells?
Secretin (cAMP)
44
What compounds stimulate the release of CCK from the duodenal I cells?
AAs and FAs
45
What effect does trypsin have on the release of CCK from duodenal I cells?
Inhibitory
46
Why is secretin-stimulated secretion richer in HCO3- than acinar secretion?
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
Describe the negative feedback loop involved in the control of HCO3- secretion in ducts?
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
Does CCK alone have any effect on HCO3- secretion?
No
49
When does CCK have an effect on HCO3- secretion?
It markedly increases HCO3- secretion that has been stimulated by secretin.
50
What effect does secretin have on enzyme secretion?
None
51
What effect does bile and Bruner's gland secretions have on the pH?
Increase pH

BRS Gastroenterology (11 decks)

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