90% of the pancreas is exocrine, composed of
- Acini, which secrete pancreatic juice with enzymes
- Intercalated ducts, which concentrate and alkalinize that juice
- Increased flow rates \(\to\) more enzyme and bicarb secretion
- Ducts merges into main pancreatic duct in herringbone pattern \(\to\) common bile duct \(\to\) duodenum
Pancreatic juice
- 2.5L/day
- pH 8 HCO3 130mM Cl 30mM
- Rich in amylase, lipase, trypsin, elastase; most secreted as inactive zymogens
Role
- Digest protein, lipid
- Neutralize stomach acid \(\to\) protect duodenal mucosa
- \(\uparrow\)pH to activate pancreatic enzymes
Secretion is
- Increased by CCK, secretin
- Decreased by catecholamines, somatostatin
Enzymes
- Trypsinogen \(\to\) converted to trypsin by enteropeptisase in duodenum
- Trypsin then activates other zymogens (including more trypsinogen)
- Trypsin (endopeptidase): large peptides \(to\) small peptides
- Carboxypeptidase (exopeptidase): small peptides \(\to\) amino acids
- Pancreatic lipase: trigs \(\to\) glycerol and FFAs
- Amylase: starch/glycogen \(\to\) mono/disaccharides
- Nuceases: DNA/RNA \(\to\) nucleotides