Alimentary Systems 4 - Pancreas Flashcards Preview

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Flashcards in Alimentary Systems 4 - Pancreas Deck (21)
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1
Q

Briefly describe pancreatic development

A
  • Develops as a foregut derivative, involving dorsal and ventral buds. Ventral is part of the hepatobiliary bud.
  • Duodenum rotates to form a C shape - ventral bud swings round and both fuse
  • Ventral bud becomes the main pancreatic duct
  • Acini grow first then the fleshy islets
2
Q

List the components of the pancreas moving outwards

A
  • Head
  • Uncinate (ventral bud)
  • Neck
  • Body
  • Tail
3
Q

How does pancreatic juice reach the duodenum?

A

Through the main and pancreatic ducts

4
Q

Describe the location of the pancreas

A

On the posterior abdominal wall extending from the C shaped duodenum to the hilum of the spleen

5
Q

List the relations of the pancreas

A
  • Posterior relations include IVC, abdominal aorta and left kidney
  • Close relations with the coeliac and superior mesenteric arteries
6
Q

List the three endocrine secretions of the pancreas.

A
  • Insulin promotes glucose transport, reduces blood glucose, and promotes protein synthesis
  • Glucagon increases gluconeogenesis and glycogenolysis
  • Somatostatin inhibits production of many hormones
7
Q

What are the two functional parts of the pancreas?

A
  • 2% endocrine, islets of Langerhans

- 98% exocrine secretes pancreatic juice into the duodenum

8
Q

Describe the appearance of the acini

A
  • Grape like clusters

- Secrete pro-enzymes into ducts

9
Q

How are the islets composed?

A
  • 15-20% a-cells which secrete glucagon
  • 60-70% b-cells which secrete insulin
  • 5-10% somatostatin
10
Q

What are the two components of pancreatic juice?

A
  • Low volume, viscous enzyme rich (produced by acinar cells)

- High volume, watery, HCO3-rich produced by duct and centroacinar cells

11
Q

Why is bicarbonate secretion in the pancreas important?

A
  • Produced by duct and centroacinar cells
  • Neutralises chyme from the stomach raising pH and preventing damage
  • Washes low volume enzyme secretion out of the pancreas
12
Q

Describe the effect of duodenal pH on bicarbonate secretion rate

A
  • pH < 3 causes little increase in bicarbonate secretion, as bile also contains bicarbonate and neutralises chyme, and brunners glands also secrete alkaline
  • pH <5 causes a significant increase in pancreatic bicarbonate secretion
13
Q

Describe the mechanism of pancreatic bicarbonate secretion

A
  • Catalysed by carbonic acid, separation of hydrogen bicarbonate
  • Na+ is moved down its gradient through paracellular tight junctions
  • Water follows
  • At the lumen, there is Cl/HCO3 exchange, with Na/H exchange at the basolateral membrane
  • Na gradient maintained by sodium potassium pump
  • Potassium is then returned to the blood by K channels
  • Chloride is returned to the lumen via chloride channels
14
Q

Where are enzymes for digestion of fat, proteins and carbohydrates synthesised and stored in the acinar cells?

A

Zymogen granules (proenzymes)

15
Q

How are acinar cells protected from damage by enzymes it produces?

A
  • Proteases released as proenzymes
  • Trypsin inhibitor produced
  • Enzymes are only activated in the duodenum
16
Q

What happens when there is blockage of the pancreatic duct?

A

Blockage of the pancreatic duct results in auto-digestion (acute pancreatitis)

17
Q

How are pancreatic enzyme functions controlled?

A
  • Altered proportions due to diet

- Lack of enzymes and bile can result in malutrition even if diet is ok

18
Q

How are pancreatic secretions controlled?

A
  • Vagus nerve (cholinergic)
  • Cephalic and gastric phase secretion due to ACth
  • Intestinal phase (70-80% of pancreatic secretion) is hormonally controlled
  • Bicarbonate controlled by secretin
  • Enzyme secretion controlled by the vagal reflex and cholecystokinin
19
Q

Compare the action in the cell of secretin and cholecystokinin

A
  • Secretin uses cAMP

- Cholecystokinin controlled by Ca2+/PLC

20
Q

How are CCK and secretin switched off?

A
  • CCK swtiched off when the cepalic phase ends, and fats and peptides are removed
  • Secretin is switched off when the pH increases
21
Q

How do CCK and secretin act separately and interact?

A
  • CCK alone has no effect on bicarbonate secretion, while it can increase bicarbonate secretion significantly once stimulated by secretin
  • Secretin has no effect on enzyme secretion