Exocrine and endocrine pancreas Flashcards
exocrine pancreas overview
releases bicarbonate, Zymozans and enzymes
endocrine pancreas overview
insulin, Glucagon, somatostatin, pancreatic polypeptide
vast majority of pancreas=
exocrine
10% of pancreas=
endocrine
2 structures that make up the exocrine pancreas
intercalated ducts
Acinus
what is an acinus
a cluster of cells that resembles a many lobed berry
what structure leads directly away from the acinus
intercalated ducts
what do the intercalated ducts feed into
intralobular ducts (eventually ending up in the pancreatic duct)
what is present where the acinus meets the intercalated ducts
aciner cells
what is the function of the intercalated ducts
to produce bicarbonate
what is bicarbonate used for
to buffer the acidic environment to a pH optimal for enzymes to work
what coverts CO2 and H2O to bicarbonate
Carbonic anhydrase
what enzyme triggers the expulsion of bicarbonate
secretin
what does secretin trigger inside the cell
ATP–> cyclic AMP
what does cyclic AMP cause
expulsion of CL- and K+
what does the activation of basolateral K+ channels do
hyperpolarises the cell
what does cell polarisation favour
Apical CL- efflux through cAMP activated CL- channels (CFTR)
how is CL- bought back into the cell
by the CL-/HCO3- exchange
what enzyme is released for digestion of fat and protein
cholecytokinin (CCK)
Where is cholecytokinin released from
I cells in the duodenum
where does cholecytokin act and what is its role
in the pancreas so the appropriate enzymes that degrade fat are released
what does secretin regulate
water homeostasis and secretions in stomach and duodenum
what does secretin do in the intercalated ducts
makes the ducts function to produce bicarbonate
where is secretin produced
S cells in the duodenum
in cystic fibrosis where and what is the gene mutation
frameshift mutation in the cystic fibrosis conductance regulator (CFTR) gene
what does cystic fibrosis lead to
viscous secretions that block exocrine movement of digestive enzymes
what eventually happens to the exocrine pancreas in a patient with cystic fibrosis
digestive enzymes stay in the pancreas and start digesting the pancreas
what enzyme can be given to aid digestion
Pancreatin
what does pancreatin contain
amylase
lipase
protease
what coating does pancreatin have
enteric coating
4 cells of the endocrine pancreas
Beta cells
Alpha cells
Delta cells
Epsilon cells
what does alpha cells produce
glucagon
what do beta cells produce
insulin
what do delta cells produce
somatostatin
what do epsilon cells produce
Ghrelin
where is insulin encoded
chromosome 11
where does insulin enter upon release from the beta cells
the portal circulation and is carried to the liver
what happens to the proportion of insulin not broken in the liver
it is degraded in the kidneys
2 forms of insulin
Hexameric form
Monomeric form
active form of insulin=
monomeric form
inactive form of insulin
Hexameric form
shape of hexameric insulin
6 insulin molecules arranged in a three fold symmetry held together by a central zinc molecule forming histidine bonds
shape of monomeric insulin
alpha and beta chains linked via disulphide bridges
what is the original single polypeptide of insulin
preproinsulin
what does preproinsulin produce after 1 peptide is cleaved
proinsulin
when proinsulin matures what does it release
Central C-peptide
what glucose receptor is on beta cells
GLUT2
when does GLUT2 open
when glucose levels are high in surrounding cells
what does the influx of glucose into the beta cell cause
increase ATP causing potassium channels open—> Depolarisation causing an influx of Calcium triggering vesicles holding hexameric insulin to release the insulin in monomeric form
what glucose receptor is stored in vesicles in muscle and Fat cells
GLUT4
what triggers the movement of GLUT4 to the cell
IRS-1 phosphorylation
what can insulin be described by
glucose haemostat
what is the principal organ of glucose homeostasis
the liver
where is 90% of glucose derived from
liver glycogen and hepatic gluconeogenesis
which organ is the main glucose consumer
the brain
what is the brains uptake of glucose controlled by
Its OBLIGATORY (not controlled by insulin)
what are other tissues glucose consumers
faculative
glycogen synthesis
glycogenesis
glycogen breakdown=
glycogenolysis
glucose breakdown=
glycolysis
what does somatostatin do
inhibits release of insulin and glucagon as well as exocrine pancreatic secretions
when and why is somatostain released
after a meal to dampen the whole process down
