The pancreas

Question 1

How does the pancreas develop?

Answer 1

Foregut and midgut derivative

• dorsal and ventral buds at the junction of f and m
• ventral is part of hepatobiliary bud

Then, duodenum rotates, forming C shape, taking ventral bud with it, allowing it to fuse with dorsal bud.

Question 2

What are the different areas of the pancreas>

Answer 2

Head neck body tail and uncinate

- tail . - islet most common in tail

Question 3

Where is the pancreas?

Answer 3

Under . stomach, medial to ileum and side to the spleen

LIES ON POSTERIOR . ABDOMINAL WALL

Supplied by mesenteric artery and coeliac artery

Question 4

Endo v exo crine

Answer 4

Endo - secretion into blood - effect on distant target organ 2PERCENT
INSULINGLUCAGONSOMATOSTATIN
Exo . - secretion into duct for direct effect 98PERCENT - digestion

Question 5

How can pancreatic cells be differentiated?

Answer 5

Exocrine

• ducts
• acini - secrete pro-enzymes

Endocrine

• derived from branch
• lose contact and form islets
• further differentiation into alpha or beta cells

Question 6

Describe islet composition

Answer 6

alpha - 15pc
beta - 60pc
delta - 10pc

Question 7

What are the parts of pancreatic juice?

Answer 7

bicarbonate
enzyme
released by diff cells

• acinar cells - enzyme release
• duct and centroacinar cells - diff part, not enzymes as no secretory granules

Question 8

What is the functional unit of the exocrine pancreas and how does it look?

Answer 8

Acinar

- blind ended tubule

Question 9

How is bicarbonate secreted? - include mechanism

Answer 9

From duct and centroacinar cells

Catalysed by carbonic anhydrase

leading to the formation of HCO3- from carbonic acid.

Na+ moves through tight junction, bringing water with it and forming the liquid part

HCO3- is exchanged for a Cl-

Protons are pumped out into blood - opp end by secondary active transport

Na gradient maintained by Na/K pump

Question 10

What is the function of the bicarb secretion

Answer 10

Helps neutralise acidic chyme and stops burning of mucosa

raises pH for enzymes to work

Watery base allows . washing of enzymes down to duodenum - prevents buildup

Question 11

Why might bicarbonate secretion stop at pH 5

Answer 11

Because there are other mechanisms that help neutralsie acid

• Bile has bicarb for chyme

Brunners gland secrete alkaline fluid

Question 12

How does CF arise?

Answer 12

Mutation of gene but, Cl- channel broke so the secretions are much thicker

Question 13

How does the splitting of H2CO3 differ in stomach and pancreas?

Answer 13

The H+ in stomach goes to gastric juice, whereas in pancreas it goes to the blood.

The HCO3- goes to blood in stomach but pancreatic juice in pancreas

Thus, the gastric venous blood is alkaline, whereas pancreatic is acidic.

Question 14

How are enzymes secreted? Are they active? What happens?

Answer 14

Acinar cells

Enzymes that break all fats, carbs and proteins,

Stored in zymogen granules
- pro-enzymes

Hence, they are only activated in the duodenum
- trypsin inhibitor

Question 15

What might occur if the pancreas were to become blocked?

Answer 15

Overload protection and result in auto-digestion due to accumulation of trypsin that becomes active.

This is acute pancreatitis

Question 16

Why might pancratic function differ?

Answer 16

Adaptations to diet

- fat high, low protein diet etc

Question 17

Without pancreatic enzymes, what might occur? Give an example . of drugs that utlise this

Answer 17

Malnutrition, due to the inability to digest foods and obtain nutrients.

Orlistat - lipase inhibitor
- Stops fat digestion and hence intestinal fat absorption
But, leads to steatorrhea

Question 18

What can cause steatorrhea?

Answer 18

CF
Chronic pancreatitis
Orlistat

Question 19

Which nervous system controls the pancreatic secretion?

Answer 19

Autonomic system

• Parasympathetic
  
  • Cholinergic
  • VAGUS NERVE

Question 20

How is pancreatic secretion controlled?

Answer 20

Cephalic phase

• reflex to smell
• enzyme mobilisation

Gastric
- pancreatic stimulation by food in stomach

Intestinal

• HORMONAL, when gastric chyme enters duodenum
• Stimulates both components of the juice

Question 21

What controls secretion of bicarbonate and enzymes?

Answer 21

Bicarb - Secretin - (cAMP_

• purely hormonal
  
  • Presence of acid - senses protons
  • Hence, gastric acid becomes less acidic and then decreases action of secretin

Enzyme - Cholecyostokinin - (PLC)

• hormonal and vagal reflex
  
  • peptide and fat levels
  • has sensors
  • cuases CCK release which goes to acinar cells
  • Acinus releases proenzymes

Question 22

What is the importance of secretin?

Answer 22

First hormone found

Question 23

What is the other role of CCK

Answer 23

Bile secretion stimulation -

smooth muscle contracts due to it

Question 24

How is CCK switched off?

Answer 24

Once fats and peptides digested, nothing to stimulate in the lumen

May be other mechanisms

Question 25

Which hormones cause bicarbonate release?

Answer 25

CCK and secretin both needed!

• CCK has no effect on bicarb secretion
• Secretin has a little effect
• Secretin has no effect on enzyme secretion

Question 26

Describe the cascade that occurs following the entrance of food into the stomach

Answer 26

Food mixed in sdtomach

Chyme squirted into duodenum

H+ in duodenum causes secretin release, which causes pancreatic juice release - bicarb

Peptides and fat cause rise in CCK - leading to enzyme release