pancreatic exocrine function

Question 1

where is the pancreas

Answer 1

deep in the retroperitoneum

Question 2

function of pancreas

Answer 2

1. endocrine secretion
2. exocrine secretion

Question 3

describe exocrine gland of pancreas

Answer 3

contains the acinar and duct tissue,

Question 4

describe endocrine gland of pancreas

Answer 4

contains the islets of Langerhans.

Question 5

what is majority of pancreas made up of

Answer 5

the exocrine portion (85% by mass)

Question 6

what does the exocrine portion do

Answer 6

secretes digestive enzymes, water and bicarbonate to assist in digestion.

Question 7

what does bicarbonate do ( 2 roles)

Answer 7

1. helps in neutralising stomach acid -

important because the small intestine is not specialised to withstand the strong acids from the stomach

this is because the small intestine, unlike the stomach, lacks a thick protective mucous layer

2. the digestive enzymes secreted by the pancreas reach their optimum function at a basic pH

this is achieved by the bicarbonate secretions of the pancreas.

Question 8

what is the functional unit of the exocrine pancreas

Answer 8

includes the acinus and its duct system

Question 9

what are acinar cells specialised in

Answer 9

enzyme synthesis, storage and secretion.

Question 10

what does the duct system do

Answer 10

modifies the aqueous secretions.

this mechanism is stimulated by the parasympathetic system and inhibited by the sympathetic system.

Question 11

describe digestive enzyme secretion

Answer 11

1. acinar cells produce digestive enzymes on the ReR
2. they are then moved to the to the Golgi complex where they form condensing vacuoles.
3. These condensing vacuoles are then concentrated into inactive zymogen granules in pancreatic acinar cells and stored for secretion.
4. They are secreted into the main pancreatic duct, which merges with the bile duct at the head of the pancreas and forms the Ampulla of Vater.
5. From here it enters the duodenum.

Question 12

which digestive enzymes are secreted

Answer 12

1. proteases
2. pancreatic lipase
3. amylase

Question 13

describe proteases

Answer 13

Chymotrypsinogen and Trypsinogen

Digest proteins and peptides to single amino acids

Question 14

describe pancreatic lipases

Answer 14

Digests triglycerides, monoglyceride and free fatty acids

Question 15

describe amylase

Answer 15

Starch and maltose (disaccharides)

Question 16

how is carbonic acid formed (H2CO3).

Answer 16

when water and carbon dioxide combine

catalysed by the enzyme carbonic anhydrase

Question 17

what does carbonic acid disassociate into

Answer 17

hydrogen ions (H+) and bicarbonate ions (HCO3–)

H2CO3 -> H+ + HCO3–

Question 18

what happens to H+ ions

Answer 18

they are transported out of the pancreatic ductal cells into the blood in exchange for Na+ ions by an H+/Na+ antiporter.

The Na+ ions that enter the cell are then removed by the Na+/H+/ATPase.

Question 19

what happens to the HCO3– produced from the dissociation of carbonic acid

Answer 19

it is transported into the intercalated ducts of the pancreas in exchange for Cl–.

An intracellular build up of Cl– is avoided by a chloride channel which allows chloride ions to return to the lumen of the intercalated ducts.

Question 20

what happens to the bicarbonate ions, Na+ ions and wate

Answer 20

they move through the intercalated ducts and end up at the main pancreatic duct ready for secretion into the duodenum upon an appropriate stimulus.

Question 21

how much bicarbonate secretion

Answer 21

total 1 litre/24 hours

Question 22

how much bicarbonate secretion

Answer 22

total 1 litre/24 hours

Question 23

what stimulates the pancreas to secrete enzymes

Answer 23

vagal innervation to the pancreas

this occurs when we see, smell or taste food
or
when the stomach wall is stretched.

Question 24

what stimulates the pancreas to secrete enzymes

Answer 24

vagal innervation to the pancreas

this occurs when we see, smell or taste food
or
when the stomach wall is stretched.

Question 25

what does acidic chyme entering the duodenum stimulate

Answer 25

stimulates S cells to release secretin - a hormone that causes the pancreatic cells to secrete the alkaline parts of the pancreatic juices.

Question 26

what do the fatty acids and protein present in the chyme, combined with the acidic pH stimulate

Answer 26

trigger I cells in the duodenum to release the hormone cholecystokinin (CCK). this hormone also leads to secretion of digestive enzymes in the pancreatic juices. also CCK stimulates bile secretion via gallbladder contraction.

Question 27

where is the main pancreatic duct anatomically

Answer 27

it merges with the bile duct, which leads to the Ampulla of Vater. It is here that these secretions pour into the duodenum and help neutralise and digest chyme.

Question 28

how does the digestion of fats and proteins affect pancreatic secretion

Answer 28

as proteins and fats are digested and absorbed pH rises stimuli for CCK and secretin disappear pancreatic secretion reduces.

Question 29

role of gastrin and CCK

Answer 29

stimulate enzyme secretion and neutralise gastric acid entering small intestines

Question 30

symptoms of pancreatic exocrine insufficiency

Answer 30

maldigestion diarrhoea steatorrhoea weight loss

Question 31

consequences of pancreatic exocrine insufficiency

Answer 31

malnutrition oesteoporosis increased cardiovascular morbidity symptom burden

Question 32

treatment of pancreatic exocrine insufficiency

Answer 32

- pancreatic enzyme replacement therapy - STOP smoking - bone health assessment - treat the underlying cause

Question 33

what initiates protein digestion

Answer 33

pepsin in the stomach

Question 34

where does majority of protein digestion occur

Answer 34

in the small intestine

Question 35

how are pancreatic proteases stored

Answer 35

as proenzymes (trypsinogen and chymotrypsinogen)

Question 36

what activates trypsinogen

Answer 36

enterokinase

Question 37

what does trypsin activate

Answer 37

chymotrypsinogen and additional trypsinogen

Question 38

what do lipases do

Answer 38

hydrolyse triglycerides to monoglyceridees and free fatty acids

Question 39

what do bile salts do

Answer 39

aid triglyceride digestion and absoprtion of monoglycerides and free fatty acids

Question 40

what is fat digestion dependent on

Answer 40

pancreatic and hepatic secretion

Question 41

where is cholecystokinin produced

Answer 41

I cells of duodenum & jejunum

Question 42

what stimulates cholecystokinin

Answer 42

HCL proteins ans fats entering duodenum

Question 43

what does cholecystokinin do

Answer 43

causes pancreatic enzyme and HCO3- secretion gallbladder contraction inhibition of gastric acid secretion delays gastric emptying

Question 44

where is secretin produced

Answer 44

upper small intestine

Question 45

what stimulates secretin

Answer 45

low duodenal pH

Question 46

what does secretin do

Answer 46

causes pancreatic water and bicarbonate secretion

Question 47

where is gastrin produced

Answer 47

G cells in stomach

Question 48

what stimulates gastrin

Answer 48

gastric distension and irritation

Question 49

what does gastrin do

Answer 49

HCl secretion - parietal cells enzyme release - acinar cells

Question 50

which cells secrete HCO3- (bicarbonate)

Answer 50

duct cells - epithelial cells lining the ducts

Question 51

which cells secrete digestive enzymes

Answer 51

gland cells at the pancreatic end of the duct system the enzymes secreted are either active or precursors

Question 52

give 2 active enzymes

Answer 52

alpha amylase lipase

Question 53

what does alpha amylase do

Answer 53

converts starch to maltose

Question 54

what does lipase do

Answer 54

Converts triglycerides to monoglyceride & fatty acids

Question 55

what does zymogen do

Answer 55

protects pancreatic cells from autodigestion

Question 56

what is enterokinase

Answer 56

is a proteolytic enzyme that splits off a peptide from pancreatic trypsinogen forming the active enzyme TRYPSIN

Question 57

what is trypsin

Answer 57

a proteolytic enzyme which in turn goes on to active other pancreatic zymogens once activated by splitting off peptide fragments

Question 58

what do trypsin & chymotrypsin do

Answer 58

chymotrypsin are enzymes used to break peptide bonds in proteins to form peptide fragments i.e. they digest ingested proteins

Question 59

what inhibits pancreatic exocrine secretion

Answer 59

somatostatin produced by the D cells in the pancreatic islets/ islets of Langerhans

Question 60

how does somatostatin inhibit exocrine secretion

Answer 60

through the inhibition of cholecystokinin-stimulated enzyme secretion and secretin-stimulated bicarbonate secretion

Question 61

what are the 4 cell types in the islets of langerhans

Answer 61

* Alpha cells - produce glucagon * Beta cells - produce insulin & amylin * Delta/D cells - produce somatostatin * PP cells - produce pancreatic polypeptide

Question 62

what does autoimmune destruction of the islets of langerhans cause

Answer 62

diabetes mellitus

Question 63

what are the 3 phases of pancreatic secretion

Answer 63

- cephalic - gastric - intestinal

Question 64

what initiates the cephalic phase

Answer 64

the sensory experience of seeing & eating food

Question 65

what happens in cephalic phase

Answer 65

involves parasympathetic vagus nerve stimulation of acinar cells to produce digestive enzymes

Question 66

what initiates gastric phase

Answer 66

the presence of food within the stomach

Question 67

what happens in gastric phase

Answer 67

also involves parasympathetic vagus nerve stimulation of acinar cells to produce digestive enzymes

Question 68

what happens by the end of the cephalic & gastric phases

Answer 68

the pancreatic ducts are filled with inactive digestive zymogens ready for release into the intestinal lumen along with bicarbonate via the sphincter of Oddi

Question 69

what happens when amino acids + fatty acids are present in the duodenum

Answer 69

then CCK is released and the gallbladder contracts inducing enzyme secretion

Question 70

what initiates the intestinal phase

Answer 70

the emptying of stomach contents into the small Intestine

Question 71

what happens in the intestinal phase

Answer 71

involves release of both secretin and cholecystokinin which stimulate pancreatic ductal cells to synthesize aqueous sodium bicarbonate solution