Secretory functions of the pancreas (choudhury) Flashcards
what are the cells of the endocrine portion of the pancreas
islet cells of langerhan
what are the cells of the exocrine portion of the pancreas
acinar cells
duct cells
what do acinar cells secrete in the pancreas
pancreatic enzymes
what do duct cells in the pancreas secrete
aqueous NaHCO3- solution
what cells of the pancreas produce glucagon
alpha (A cells)
what cells of the pancreas produce insulin
Beta (B cells)
what cells of the pancreas produce somatostatin
D cells
what cells of the pancreas produce pancreatic polypeptide
pp cells
what is the effect of sympathetics on pancreas?
parasympathetics ?
inhibited by sympathetic &
-
stimulated by parasympathetic NS
what are the two ducts of the pancreas?
main pancreatic duct (Wirsung’s)
accessory collecting duct (Duct of Santorini)
what are the two components of exocrine secretions ?
aqueous bicarb component
enzymatic component
what stimulates the release of the aqueous component of the pancreatic juice
secretin
which factors stimulate acinar cells to secrete protein (enzymatic protein)
how do they increase the secretion?
ACh
CCK
Secretin
VIP
All increase intracellular Ca 2+ (second messenger) which helps vesicles fuse and release contents
Activation of protein kinases increases acinar cell secretion
all of this is to help digest fats, carbs and proteins that are in the duodenum
what is the composition of acinar cell fluid
isotonic
what are the effects of ACh and CCK on the acinar cells
stimulate NaCl secretion through phosphorylation of ion channels
what is the mechanism of action of secretin on ductal cells.
generates electrical gradient that favors Na HCO3- co-transport
(activates adenylyl cyclase, raises CAMP, stimulates protein kinase A and phosphorylates CFTR
what are 6 enzymes in the acinar enzymatic secretions
amylase- carbohydrates
trypsinogen- proteins
lipase- triglycerides **very important only one lipase
procolipase (colipase)- removes the bile from the fat particles to make room for lipase to come in and break down the fat
trypsin inhibitors = protects against trypsin in acinar and ductal cells
glycoproteins = protects against protease (mediated mucosal immunity)
how are pancreatic proteases activated
where is enterokinase located
enterokinase cleaves a hexapeptide from trypsinogen converting it to active enzyme trypsin
pancreatic proteases are secreted into the duodenum as inactive precursor
enterokinase is located in brush border of duodenal enterocytes (intestinal mucosal cells)
what are the effects of CCK
coordinates GI activity (secretion) to food contracts gall bladder relaxes the sphincter of Oddi slows gastric motility retards gastric emptying
the outcome of this is that there is matching of nutrient delivery to digestive and absorptive capacity
what molecules stimulate CCK release
CCK-RP and MP which are both proteins
what do GRP and ACh stimulate the release of
MP
what is the signficance of peptide (protein) factors regulating CCK release
this is important so that CCK can inhibit its own release and doesn’t cause digestion of the lumen
what cells release CCK
I cells
what cells release secretin
s cells in duodenal mucosa
at high rates of secretion what is the composition of pancreatic juice
alkaline
what is achlorhydric. what is it caused by what can it lead to
Achlorhydric (unable to secrete gastric acid)
causes:
- secondary to disease
- on drugs, proton pump inhibitors,bicarbonate
fail to release secretin even in presence of a
fatty meal
leads to Duodenal ulcer b/c secretin levels are too low (not enough bicarb release)
at what point do signs of malabsorption and indigestion appear
if pancreatic secretions fall below 10 percent
what are two important causes of pancreatitis
alcohol (too many triglycerides and ca)
gallstones
what is cystic fibrosis
what does this lead to
autosomal recessive genetic mutation in the CFTR Cl channel
Primarily affects caucasians
Lack chloride transporter at apical membrane
Leads to decreased water, HCO3, & Cl excretion, with concentration of protein in acinar ducts and blockage…. gland autodigestion/destruction
Progressive pulmonary and pancreatic insufficiency - chronic
at low rates of pancreatic secretion what is the composition
na and cl dominate
at high rates of pancreatic secretion what two molecules are predominate
Na and HCO3
