exocrine panceas

Question 1

exocrine pancreatic juice has 2 phases, what are they? what are their functions?

Answer 1

phase 1 = aqueous phase which HCO3- rich 
function = projects the duodenal mucosa from gastric acid and buffers chyme to a pH where enzymes can work

phase 2 = protein/enzyme rich phase
function = digestion of food stuffs

Question 2

where are the 2 phases of pancreatic juice secreted from?

Answer 2

phase 1 = striated duct cells

phase 2 = acinar cells

Question 3

what is the appearance of an unstimulated duct cell?

Answer 3

• aggregated CFTR at luminal membrane

- vesicles containing H+ pumps in the cytoplasm

Question 4

what is the appearance of a stimulated duct cell?

Answer 4

• CFTR proteins separate so can now pump out HCO3- and pump Cl- into the cell
• H+ pumps have move to the basolateral membrane and inserted so they can now pump H+ out of the cell

Question 5

Why is H+ pumped out of the duct cells into the capillaries?

Answer 5

So it can react with HCO3- in the blood giving CO2 and H2O so the CO2 can diffuse into the duct cell and utilised to form HCO3- for luminal excretion

Question 6

what enzymes are secreted in phase 2?

Answer 6

active enzymes
-amylase, lipase, trypsin

precusor enzymes/zymogens
-chymotrypsin, elastase, carboxypeptidases

Question 7

what activates zymogens secreted by the pancreas?

Answer 7

trypsin

Question 8

what stimulates the secretion if pancreatic juice?

Answer 8

duodenal distension, presence of fats, peptides and a low pH causes the secretion of…

• CCK stimulates acinar cells
• secretin stimulates duct cells

Question 9

what inhibits pancreatic juice secretion?

Answer 9

mainly somatostatin

• secreted by delta cells in the islets of langerhans and has a paracrine effect
• inhibits the secretion of CCK and secretin