Pancreas and Small bowel Flashcards
(56 cards)
Describe the features and functions of the Endocrine part of the pancreas
2% of gland
Islet of langerhans
Thy secret hormones into blood: Insulin, Glucagon, Somatostatin and pancreatic peptide
They regulate blood glucose, metabolism and growth effects
Descirbe the features and functions of the Exocrine part of the pancreas
98% of gland
Secrete pancreatic juice into duodenum via MPD or sphincter of Oddi or ampulla
Digestive function
Describe the structure an features of Acinar cells (exocrine)
They Have ducts
they are grape like clusters of secretory units
The acinar cells secret pro-enzymes into ducts
Descirbe the structure and functions of islets cells . What are the derived from? What is their distribution across pancreas?
Derived from branching duct system
lose contact with ducts to become islets
Diffrentiate into alpah and beta cells secreting into blood
There’s a greater proportion of islets in the tail of the pancreas than the head
What are the composition of the islets cells and what do they secrete?
Describe the vasculature of islets cells
- Alpha cells (15-20%)- glucagon
- beta cells (60-70%)- insulin
- Delta cells (5-10%)- somatostatin
he islets are highly vascular ensuring that all endocrine calls have close access to a site for secretion
What are the composite cells of the acini and what are their morphological features
Secretory acinar cells- large with apical secretion granules
Duct cells- small and pale
Just between the acinar cells and duct cell is the centroacinar cells
*Figure out which is which on picture*

The exocrine cells makes pancreatic juries. Descirbe the composition of the pancreatic juices made by each respective acinar cells
Acinar cells- low volume, viscous and enzyme rich
Duct and centroacinar cells- high volume, watery and HCO3- rich

What is fucntion of the Bicarbonate secretion made by the duct and centroacinar cells
120mM [H+] from stomach (plasma conc is 25mM)
It neutralises acid chyme from stomach. This prevents damage to duodenal mucosa and raises pH to optimum range for pancreatic enzymes to work
it washes low volume enzyme secretion out of pancreas into duodenum; or else it will plug out pancreatic duct
Compare the rate of HCO3- secretion with duodenal pH
When duodenal pH isa less than 5, there’s a linear increases in pancreatic HCO3- secretion
if duodenal pH is less than 3, there’s not much more increase in HCO3- secretion; the graph levels out as there’s still bile made by liver (which contains HCO3-)

Summarise the mechanism buy which HCO3- is relased from duct and centroacinar cells ?
CO2 enters and converted to HCO3- via carbonic anhydrase. HCO3- leaves cell via Cl-/HCO3- exchanger (AE1 ) in apical membrane; Cl- is now in cell
H+ (From CO2 reaction result ) leaves via H+/Na+ antiporter (NHE-1) EXCHANGER via basolateral membrane. Na+ now in cells
Na+ leaves via Na+/K+ ATPase pump and K+ enter cell via basolateral membrane
k+ returns to blood via K+ channel
The Cl- leaves the cell through the apical membrane via CFTR (cystic fibrosis transmembrane conductance regulator)

Compare the outcomes of the bicarbonate reactions in the stomach parietal cell and pancreatic duct cells
Reaction : H2O + CO2= H2CO3 = H+ + HCO3-

What enzymes are relases from acinar cells? What are they relased as
Lipases, proteases and amylase
they are sysntheised and stores in zymogen granules
Proteases released as inactive proenzyme; it protects the acini and ducts from autodigestion
What does the pancreas release that inactivate trypsin? When are the enzymes activated
Trypsin inhibitor
enzymes only activated in duodenum
blockage of Main pancreatic duct may overload it and it could cause autodigestion
Descirbe the process of how pancreatic enzymes are activated? What activates it
Duodenal mucosa secrets enterokinase/enteropeptidase. This converts trypsinogen to trypsin and trypsin converts all the other zymogen to their acitve form
Lipase requires bile salts for effective action, and also requires colipase to become its active form

How does the pancreas adapt to diet?
High protein diet and low carb diets will make pancreas release more proteases and less amylase proportion
These enzymes (and bile) are essential for absorption, if inhibited it will cause malnutrition even if dietary input is OK
Summarise the 3 phases for the control of pancreatic juice secretion
Cephalic pahse- reflex to smell or sight of food. Secrete only enzyme rich pancreatic juices (enzymes only - low volume)
Gastric pahse- distension in stomach activates this. Same mechanism as cephalic pahse
Intestinal phase- 70-80% of secretions. This is hormonal mediated when gastric chyme enters duodenum. BOTH enzymes and HCO3- enter duodenum
What controls the relases of enzymes from acini cells?
Vagus nerve- PNS cholinergic (ACh)
Cholescystokinin (Ca2+/PLC mediated)
What controls the secretion of pancreatic juices (bicarbonate) form duct and centroacinar cells
Secretin (cAMP mediated)
Summarise how vagal and CCK stimulation control enzyme secretion in acini
CCK made from duodenal I cells
The diagram shows what causes release of CCK, however CCK goes and act on pancreas as a positive feedback loop

Describe the mechanism which controls HCO3- secretion in acinar cells AND DUCTS
CCK mainly cause acinar fluid to be made- acinar fluid is isotonic to plasma (Na+,K+,Cl-, HCO3-)
Secretin stimulates secretion of H2O and HCO3- from cells lining extralobular ducts
SECRETIN stimulated secretion is richer in HCO3- cf acinar secretion becuase of Cl-/HCO3- exchange

Describe the negative feedback involved in HCO3- secretion in ducts
Lower pH in luminal duodenum is the stimulus

Outline the different stimulus that can affect rate of HCO3- secretion from ductal cells. Note any differences in outcome
Vagus nerve is similar effect to CCK
secretin has no effect on enzyme secretion
CCK and secretin stimulation GREATLY increase HCO3- secretion

Outline the summary of a meal and how it can affect pancreatic secretions . Draw flowchart

Compare the length of the components of the small bowel
Duodenum- 25cm
jejunum- 2.5m
ileum-3.75m
No sudden transition between them and they all have the same basic histology all organisation





















