Pancreas Flashcards
composition of the Pancreas
-85% is the exocrine portion -2% is islet of langerhan (endocrine protion) -rest is connective tissue, blood vessels, and nerves
main pancreatic duct joins the common bile duct to form…
sphincter of oddi - emptying of ducts into the duodenum
big difference between the salivary gland and the pancreas when it comes to their acinus and duct
-in salivary gland, duct modified the fluid produced by the acinus making isotonic fluid to hypotonic fluid -in pancreas - acinus and duct make fluid independent of each other – remains isotonic all the way through
big difference between the salivary gland and the pancreas when it comes to their acinus and duct
-in salivary gland, duct modified the fluid produced by the acinus making isotonic fluid to hypotonic fluid -in pancreas - acinus and duct make fluid independent of each other – remains isotonic all the way through
difference in fluid produced in the acinus vs. duct in pancreas
acinus - low volume enzyme rich and NaCl rich fluid duct - HCO3 rich fluid
enzymes made in the pancreas are essential for
digestion
enzymes made in the pancreas are essential for
digestion
hormones important for stimulating enzyme secretion in the pancreas
Ach from vagal afferents and CCK
how does Ach and CCK work to stimulate enzymes in the pancreas
agonists for increase in intracellular calcium which triggers fluid secretion and exocytosis
helps prevent autodigestion of the pancreas
-inactivated enyzmes, zymogens -enzymes in membrane limited vesicle (from synthesis to exocytosis) preventing contact with cytoplasm
what changes trypsinogen to trypsin
enterokinase in the small intestine
how does conversion to trypsin protect pancreas from autodigestion
conversion happens in the small intestine and not the pancreas so pancreas is protected
how does pancreas protect itself from autodigestion just in case trypsin is activated within it?
pancreas produces a trypsin inhibitor so as to protect itself PS also this way trypsin cannot activate other zymogens in the pancreas
how does pancreas protect itself from autodigestion just in case trypsin is activated within it?
pancreas produces a trypsin inhibitor so as to protect itself PS also this way trypsin cannot activate other zymogens in the pancreas
importance of the duct cells secreting NaHCO3
neutralize gastric acid in the duodenum
what happens to cations and anions with increased secretory rate in the pancreatic duct
-cations (Na+ and K+) stay constant -anions HCO3- increases while Cl- decreases
explain the pancreatic duct secretion
- HCO3- leaves into the lumen in exchange for Cl- on HCO3-/Cl- transporter
- HCO3- is used to neutralize the gastric acid from stomach
- there is a CFTR channel on the apical side to pull Cl- into the lumen to provide enough Cl- for exchange with HCO3-
- on basal side, there is a Na+/K+ pump and Na+/H+ pump
- the H+ being made in the cell is reabsorbed into the blood to neutralize the alkaline tide made by the HCO3- being excreted due to the gastric acid secretion
what happens in people with cystic fibrosis where the CFTR (Cl-) channeling is not working in the pancreatic duct
- the Cl- channel is defective so no Cl- being secreted into the lumen to help operate the HCO3-/Cl- exchanger
- HCO3- cannot be secreted without the Cl-
- so Na cannot follow the HCO3- paracellularly hence no pulling of water into the lumen
- left with dry mucus in lumen and leads to fibrosis of the pancreatic duct
most important phase for pancreatic secretion and describes large stimulation that occurs when digestive product and acid appears in the small intestine
intestinal phase
what happens in cephalic phase in response to sight, smell, taste, and anticipation of food
secretion of enzymes and bicarbonate
what governs the release of secretin
acid load entering the duodenum from the stomach
effects of secretin on pancreatic duct
increases the release of cAMP hence activating bicarbonate and fluid secretion
big difference in secretin and CCK on where they target
secretin targets the pancreatic duct for release of bicarbonate
CCK targets pancreatic acinus for release of enzymes
stimulus for cephalic, gastric, and intestinal phase of pancreas
cephalic - sight, smell, taste of food
gastric - distension
intestinal - AA, FA, Ca2+, H+, distension
mechanism that occurs in response to stimulus in cephalic, gastric, intestinal phase
cephalic - vagus
gastric - vagus and gastrin(weak agonist of CCK)
intestinal - CCK, secretin, vagus
reason for the falling phase of pancreatic secretion
disappearance of food from the upper part of the small intestine
