6. Pancreas

Question 1

What does the developing pancreas start from?

Answer 1

It arises from the foregut-midgut junction forming a ventral pancreas and dorsal pancreas

Question 2

What is the ventral bud a part of?

Answer 2

The hepatobilary bud

Question 3

What happens when the duodenum swings round?

Answer 3

It rotates to form a C shape - ventral pancreas swings round to lie next to the dorsal pancreas and fuse together

Question 4

Which bud becomes the main pancreatic duct?

Answer 4

The ventral bud

Question 5

How is the pancreas described?

Answer 5

Head, neck, body, tail and uncinate (tail)

Question 6

Where is the highest proportion of islets of Langerhans in the pancreas?

Answer 6

Tail section

Question 7

Where does the pancreatic juice enter?

Answer 7

Duodenum via the pancreatic duct

Question 8

Where does the pancreas sit in?

Answer 8

The C shape of the duodenum

Question 9

How far the does pancreas extend across?

Answer 9

It reaches the spleen

Question 10

What is posterior to the pancreas?

Answer 10

The IVC, aorta and left kidney

Question 11

Where does pancreas get its blood supply from?

Answer 11

The coeliac and mesenteric arteries

Question 12

Define endocrine

Answer 12

Endocrine is secretion of hormone into the blood. (autocrine/paracrine) ductless glands

Question 13

Define exocrine

Answer 13

Exocrine is secretion into a duct - direct local effect

Question 14

What is insulin

Answer 14

Anabolic hormone, promotes glucose transport into cells and storage as glycogen, reduces blood glucose level, promotes protein synthesis and lipogenesis

Question 15

What is glucagon

Answer 15

Increases gluconeogenesis and glycogenolysis (increases blood glucose)

Question 16

What is somatostatin

Answer 16

Suppresses the release of a lot different hormones. ‘endocrine cyanide’

Question 17

What are the two functional parts of the pancreas?

Answer 17

Endocrine and exocrine

Question 18

How much of the pancreas is made up of endocrine glands?

Answer 18

2%

Question 19

How much of the pancreas is made up of exocrine glands?

Answer 19

98%

Question 20

What is an example of an endocrine gland?

Answer 20

Islets of Langerhans

Question 21

What does the exocrine glands secrete?

Answer 21

Secretes pancreatic juice into the duodenum via the pancreatic duct/common bile duct, It has digestive function

Question 22

How do pancreatic diseases affect the 2 functional parts of the pancreas?

Answer 22

It effects both exocrine and endorine effect e.g cystic fibrosis

Question 23

What structures exist from the ducts of the pancreas?

Answer 23

Acini and islets

Question 24

Where does the endocrine tissue arise from?

Answer 24

It is derived from branching duct system, loses contact with ducts to form islets

Question 25

Where does exocrine tissue originate from?

Answer 25

Ducts which have acini

Question 26

What are acini?

Answer 26

Grape like clusters of secretory unit

Question 27

What do acini secrete?

Answer 27

They secrete pro-enzymes stored in zymogen granules into ducts

Question 28

Describe the composition of alpha, beta and delta cells in the islets of Langerhans

Answer 28

15-20% are a-cells - glucagon 60-70% are b-cells - insulin 5-10% are d-cells - somatostatin

Question 29

Why are the islets highly vascularised?

Answer 29

To ensure that all the cells have close sites for secretion

Question 30

What lines a pancreatic duct?

Answer 30

Columnar epithelium

Question 31

What are the two components of pancreatic juice?

Answer 31

Low volume, viscous, enzyme rich - acinar cells | High volume, watery, HCO3- rich - duct cells

Question 32

What are centroacinar cells?

Answer 32

Join the duct and acinar cells

Question 33

What is function of the bicarbonate secretion?

Answer 33

1) neutralises acid chyme from stomach | 2) washes low volume enzyme secretion out of pancreas into duodenum

Question 34

Why is the acid chyme neutralised?

Answer 34

To prevent damage to endothelium and raise pH for optimum range for pancreatic enzymes to work

Question 35

What is the concentration of bicarbonate in the secretion?

Answer 35

120 mM

Question 36

What happens when duodenal pH falls?

Answer 36

The rate of bicarbonate secretion increases. It plateaus at pH 3

Question 37

What helps the pancreas to neutralise the acid chyme?

Answer 37

Brunners gland in the duodenum (small intestine) and bile also contains bicarbonate

Question 38

How is bicarbonate secreted out of the pancreas?

Answer 38

1) H+ and HCO3- is produced - catalysed by carbonic anydrase 2) Na+ moves into the lumen via tight junctions by diffusion. H2O follows 3) The HCO3- is then exchanged with Cl- at the lumen, driven by electrochemical gradient 4) The H+ is then exchanged with Na+ at the basal lateral membrane, driven by electrochemical gradient 5) the Na+ gradient is maintained from the sodium potassium exchange pump - uses ATP 6) Any potassium brought in by the pump then diffuses back into the blood by K-channels 7) Cl- returns to the lumen via Cl-channels, this ensures that there will still be Cl- to exchange the HCO3- with

Question 39

What does cystic fibrosis effect?

Answer 39

The CFTR, which causes the chloride channel to not work

Question 40

What is synthesised and stored in zymogen granules?

Answer 40

pro-enzymes (lipases, proteases and amylases)

Question 41

How are proteases released from the zymogen granules?

Answer 41

inactive - protects the acini and ducts from self digestion

Question 42

What prevents trypsin activation?

Answer 42

trypsin inhibitor

Question 43

When do the enzymes become activated?

Answer 43

In the duodenum

Question 44

What can cause acute pancreatitis?

Answer 44

Blockage of the pancreatic duct - overload protection causing autodigestion

Question 45

What and where is trypsin activated?

Answer 45

Activated by enterokinase in the duodenum. trypsinogen to trypsin

Question 46

How does the pancreas adapt to diet?

Answer 46

It changes the proportion of different enzymes it secretes

Question 47

What is essential for normal digestion of meal? Lack of these can lead to malnutrition

Answer 47

Pancreatic enzymes and bile

Question 48

What does orlistat do?

Answer 48

It inhibits pancreatic lipases - causing steatorrhoea (fatty stool)

Question 49

How is orlistat used?

Answer 49

Anti-obesity drug - weight loss agent

Question 50

What is the role of the vagus nerve?

Answer 50

Parasympathetic stimulation. Cholinergic and communicates information from gut to brain and vice versa

Question 51

Which phase causes most of pancreatic secretion?

Answer 51

The intestinal phase causes 70-80% of pancreatic secretion. This is hormonally mediated

Question 52

What is the bicarbonate secretion controlled by?

Answer 52

Secretin (caMP)

Question 53

What is enzyme secretion controlled by?

Answer 53

Cholecystokinin CCK (Ca2+/PLC)

Question 54

What does CCK also stimulate?

Answer 54

Bile secretion

Question 55

What do lipases need to work?

Answer 55

Bile salts

Question 56

What releases secretin?

Answer 56

H+ binds to enteroendocrine cells in the duodenum which releases secretin into the blood.

Question 57

What effect does the HCO3- have on the duodenum?

Answer 57

It increases pH in the lumen switching off secretin secretion

Question 58

What releases CCK?

Answer 58

Peptides and fats bind to enteroendocrine cells which releases CCK into the blood

Question 59

What can stimulate the acinus?

Answer 59

Vagus - ACh | CCK in the blood

Question 60

How is CCK release switched off?

Answer 60

Absorption of fats and peptides removes the local luminal stimulus for CCK release

Question 61

What has a synergistic effect on the release of bicarbonate?

Answer 61

CCK + Secretin