Editing Pancreas (section)

== '''Physiology''' ==

=== '''Exocrine''' ===

** Creation of enzymes
*** Provides most of the       enzymes for alimentary digestion - lipase, amylase, trypsin,       chymotrypsin, carboxypeptidase, and elastase
*** Enzymes are synthesised by       acinar cells as inactive proenzymes
**** Acinar cells also        synthesis pancreatic secretory trypsin inhibitor, which counteracts        premature activation - encoded by ''SPINK1'' gene, which if faulty,        leads to chronic pancreatitis, especially in childhood
*** Proenzymes can then be       secreted into the pancreatic duct, and eventually the duodenal lumen
*** Duodenal brush border cells       express enterokinase, which catalyses the enzymatic activation of       trypsin from trypsinogen
** Pancreatic ductal cells
*** Primary function is to       provide the water and electrolytes necessary to dilute and deliver the       enzymes
*** Stimulated to release these       substances by secretin
** Secretion of bicarb
*** Bicarb produced and       secreted to neutralise the HCl secreted by stomach
*** Pancreatic enzymes would be       deactivated at low pH - optimal pH is >7
** Regulation of secretion
*** Cephalic phase - stimulated       by vagus nerve - increased acinar secretion of enzymes
*** Gastric phase - vagovagal       reflexes triggered by gastric distension - increased acinar cell       secretion
*** Intestinal phase (most       important - majority of secretion) - mediated by secretin (from S cells)       and CCK, in response to acidification of duodenum
**** Secretin receptors on        pancreatic ductal cells but not present in other pancreatic cells
**** Secretin stimulation        activates bicarb-chloride anion exchanger in the apical membrane of        ductal cells, causing secretion of bicarb
**** CCK is the main mediator        of the secretion of enzymes, and relaxation of the sphincter of Oddi
*** Islet cells regulate       exocrine function
** Function of enzymes
*** Amylase hydrolyses major       polysaccharides into smaller ones
*** Lipase hydrolyses ingested       fats into FFAs and 2-monoglycerides

=== '''Endocrine''' ===

** Glucose homeostasis
*** Insulin is secreted by B       cells within islets of Langerhans, and promotes glucose transport into       cells, inhibits glycogenolysis and fatty acid breakdown, and stimulates       protein synthesis.
**** Promotes glucose transport        into all cells except B cells, hepatocytes and CNS cells.
**** Synthesised as proinsulin        in response to pancreatic B cell stimulation. Transported to Golgi        complex where it is cleaved into insulin and C-peptide, which are        secreted in equimolar amounts.
*** Glucagon increases blood       glucose levels through stimulation of glycogenolysis, lipolysis, and       gluconeogenesis
**** Secreted by A cells
** Somatostatin
*** Secreted by islet D cells
*** When administered       exogenously, inhibits the release of insulin, glucagon, PP and inhibits       gastric, pancreatic and biliary secretions
** Pancreatic polypeptide (PP)
*** Secreted by islet F cells
*** True physiological role       unclear - infusion causes loss of appetite and reduced food intake
** VIP
** Amylin
** Galanin
** Serotonin

[[Category:Anatomy]]