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Pancreatic Juice: Composition, Function & Digestive Role

Pancreatic Juice: Composition and Digestive Function

The pancreas secretes 1.5–3 L/day of alkaline fluid (pH 7.5–8.5) rich in enzymes and bicarbonate.

Composition

  • Water & Electrolytes: HCO₃⁻ (bicarbonate) ~100–140 mEq/L — neutralizes gastric acid.
  • Enzymes (zymogens activated in duodenum):
    • Amylase: Starches → maltose, maltotriose, α-limit dextrins.
    • Lipase (+ colipase): Triglycerides → 2-monoglyceride + 2 fatty acids.
    • Proteases: Trypsinogen → trypsin (enteropeptidase) → activates others.
      • Trypsin, chymotrypsin, elastase, carboxypeptidases A/B → peptides/amino acids.
    • Nucleases: DNA/RNA → nucleotides.

Regulation

  • Cephalic phase: Vagal stimulation → enzyme-rich, low-volume secretion.
  • Gastric phase: Gastric distension/peptides → vago-vagal reflex.
  • Intestinal phase (major):
    • Secretin (S cells, duodenum) → HCO₃⁻-rich secretion (neutralizes acid).
    • CCK (I cells, duodenum) → enzyme-rich secretion (stimulated by fats/amino acids).

Clinical Relevance

  • Pancreatic insufficiency (CF, chronic pancreatitis): Steatorrhea, weight loss, fat-soluble vitamin deficiency. Treated with pancreatic enzyme replacement therapy (PERT).
  • Acute pancreatitis: Premature intra-pancreatic enzyme activation → autodigestion.
  • Diagnostic: Serum amylase/lipase (lipase more specific); fecal elastase (exocrine function).

Pancreatic juice is the primary digestive enzyme source; bicarbonate creates the permissive pH for intestinal enzymes.

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