pancreatic and intestinal secretions Flashcards
what two functions do the pancreas have and what do they secrete
endocrine - glucagon and insulin into the blood
exocrine - lipases, proteases and amylase into ducts that lead directly to the duodenum
what secretes pancreatic juice
acini
what is the ionic composition of primary pancreatic juice
high in bicarbonate and Na
low in cl
low in K
how does pancreatic juice get modified
hco3 is exchanged for cl normally so less hco3 in duodenum
what happens to the ionic composition during fast flow rates
less time for modification and higher in HCO3 which is good for neutralisation of stomach acid
what happens to the level of Na and K in pancreatic secretions
stay the same
what is the ductal pathway for pancreatic juice
acini to pancreatic duct to ampulla to sphincter of oddi to duodenum
what are the three reflex causing increase in pancreatic secretion
gastric: food in the stomach causing distension triggers the vaso vagal pathway which increase ACh and more primary secretion
cephalic: sight or smell also triggers vaso-vagal pathway
intestinal (most dominant 80%): high ph and presence of fats stimulates s cells to secrete secretin which increases pancreatic secretion. presence of aa and fats stimulates release of cck to increase secretions.
what are the two main roles of the small intestine
absorption and digestion
what enzymes does the pancreas release
trypsinogen, chymotrypsinogen and procarboxy-peptidase
what regulates activation of enzymes released from the pancreas
enterokinase released from duodenal cells
how does activation of enzymes in the duodenum work
enterokinase activates trypsinogen to trypsin which in in turn changes chymotrysinogen and procarboxy-petidase to chymotrypsin and carboxy-peptidase
what are the two main secretions from the duodenum
nahco3
nacl
what is the role of NaHCO3 in the duodenum and where does it come from
bruner cells in the duodenum mainly and its function are to neutralise acidity and favour conditions for digestive enzymes
act as a lubricant for chyme
what are the theories of NaCl release in the duodenum
maintain osmotic balance of fluids
flushing of pathogens: paneth cells at the bottom of crypts release a defensins and lysosomes
what is the role of vili
increase surface area and also have micro villi increase sa by 600x
what stimulates the release of nacl from the small intestine
release of VIP and adrenergics
what effect does VIP and adrenergics have on nacl secretion
increases cAMP and more nacl release
describe the process of cl into the lumen from the ecf
2 cl moves into the cell with 1 na and 1 k
3 na out and 2 k in
k leaves basolateral membrane across open channel
cl freely moves into the lumen
describe the process of na into the lumen
paracellular
what does the cholera toxin do
chronically stimulates cAMP via stimulates of g protein in small intestine
this causes continuous influx of cl into the lumen and water via osmosis follows producing dehydration and diarrhoea
how do you relieve symptoms of cholera
treat with ORS containing lots of salt and sugar therefore water moves back from lumen into ecf
what ion transport occurs in the colon
na and cl are reabsorbed
k and hco3 are secreted
what is colonic ion transport fuelled by
aldosterone causes uptake of Na
