Pancreas: Exocrine and Endocrine Functions Explained

The pancreas is a dual-function gland: exocrine (digestive) and endocrine (hormonal).

Exocrine Function (98% of mass)

• Acinar cells synthesize digestive enzymes → secreted as inactive zymogens into ducts.
• Key enzymes:
  • Amylase – carbohydrates → maltose, maltotriose
  • Lipase (with colipase) – triglycerides → fatty acids + monoglycerides
  • Proteases: trypsinogen → trypsin (enteropeptidase) → activates others (chymotrypsin, elastase, carboxypeptidases)
  • Nucleases – DNA/RNA
• Ductal cells secrete HCO₃⁻-rich fluid → neutralizes gastric acid, optimal pH for enzymes.
• Regulation: CCK (enzymes), secretin (bicarbonate), vagal stimulation.

Endocrine Function (Islets of Langerhans, 2% of mass)

• β-cells (60%): Insulin – ↓ blood glucose (GLUT4 translocation, glycogen synthesis, lipogenesis, protein synthesis).
• α-cells (30%): Glucagon – ↑ blood glucose (glycogenolysis, gluconeogenesis).
• δ-cells (10%): Somatostatin – inhibits insulin & glucagon.
• PP-cells (F-cells): Pancreatic polypeptide – regulates exocrine secretion, appetite.
• ε-cells: Ghrelin – hunger stimulation.

Clinical Correlates

• Exocrine insufficiency (EPI): Chronic pancreatitis, CF, pancreatic cancer → steatorrhea, weight loss → pancreatic enzyme replacement therapy (PERT).
• Diabetes mellitus: Type 1 (autoimmune β-cell destruction); Type 2 (insulin resistance + β-cell failure); Type 3c (pancreatogenic).
• Acute pancreatitis: Premature intra-pancreatic enzyme activation → autodigestion.