Pancreatic and Biliary Digestion and Disease Flashcards
What are the three enteroendocrine cells in the duodenum and what do they secrete?
I cells- cholecystokinin, sense fats and proteins
S cells- Secretin, sense low pH (acidic env.)
Enterochromaffin cells- serotonin, sense irritants and serotonin will promote gut motility
How are pancreatic enzymes activated? (proteases)
trypsinogen is converted to trypsin by enteropeptidase on cell surfaces,
Chymotrypsinogen is converted to chymotrypsin by trypsin.
Trypsin can also cleave trypsinogen
What two ways does CCK stimulate pancreatic enzyme release?
- Secreted into blood stream to pancreas where it affects acinar cells
- secreted into afferent fibres next to I cells, to vagus nerve in brainstem thus stimulating pancreatic activity via vagus nerve
Why must the duodenum be of neutral pH?
inactivate pepsin; optimum pH for enzymes; increase FA solubility; prevent mucosal damage
How is bicarbonate secreted?
- bicarbonate absorbed into cell (basolaterally) with Na+
- also water and CO2 turned into bicarbonate by carbonic anhydrase
- secretion involves CFTR transporter and HCO3- and Cl- antiport
How does secretin control bicarbonate secretion?
enters blood, binds to ductal cells, increase cAMP, increase CFTR activity, more alkaline secretion
What else does CCK do?
Causes bile production in liver, gallbladder contraction and relaxation of sphincter of Oddi
What is cystic fibrosis and how does it affect the pancreas?
autosomal recessive disease that is a mutation of te CFTR gene, can cause pancreatic insufficiency
a defective CFTR channel means no bicarbonate secreted, etc
-cells accumulate Cl-, draws Na+ and water out
-result is viscous, mucous secretion, causings blockages and increased likelihood of infection. Also build up of enzymes can cause autodigestion
What molecules are in bile?
bilirubin; bile salts; cholesterol; phospholipids
Where is bile reabsorbed?
terminal ileum
What is the function of bile?
Absorption of vitamins A, D, E and K by bile acids
removal of bilirubin in faeces
What two ways are bile flow driven?
Acid dependent- movement of bile into caniliculi actively causes water to follow
Acid independent- transport of other solutes and electrolytes
Reabsorption and secretion by ducts
What is cholestasis and what will it cause?
obstruction to bile flow, can cause increased liver and biliary tract pressure, causing tight junctions to break, causing contents to leak into circulation (jaundice)
What are gall stones?
a.k.a Cholelithiasis, primarily concentrates of cholesterol or bilirubin and bile salts, can cause biliary obstruction
What else can cause cholestasis, and what are the effects of prolonged cholestasis?
Cholangiocarcinoma or pancreatic cancer of head.
Jaundice; itchiness; nausea; malabsorption of fat.
potential palpable iliac fossa lymph node (Virchows)
