Pancreas Anatomy, Physiology, and Clinical Essentials

The pancreas is a retroperitoneal organ with dual exocrine (digestive) and endocrine (hormonal) functions. Its dysfunction underlies diabetes, pancreatitis, and pancreatic cancer.

Anatomy

• Location: Upper abdomen, L1–L2 level, transversely across the posterior wall
• Regions: Head (in C-loop of duodenum), neck, body, tail (splenic hilum)
• Ducts: Main pancreatic duct (Wirsung) joins common bile duct → ampulla of Vater → duodenum. Accessory duct (Santorini) in 70%.
• Vasculature: Celiac trunk (splenic, common hepatic, left gastric arteries) + SMA branches
• Innervation: Autonomic (vagus → secretion; splanchnic → vasoconstriction)

Exocrine Function (98% of Mass)

• Acinar cells: Secrete inactive zymogens (trypsinogen, chymotrypsinogen, procarboxypeptidase, proelastase)
• Ductal cells: Secrete HCO₃⁻-rich fluid (pH 8) — neutralizes gastric acid, optimal pH for enzymes
• Output: 1.5–3 L/day; stimulated by secretin (HCO₃⁻), CCK (enzymes), vagal input
• Activation: Enterokinase (duodenal brush border) converts trypsinogen → trypsin → activates others

Endocrine Function (2% of Mass = Islets of Langerhans)

• α-cells (20%): Glucagon → increases blood glucose (glycogenolysis, gluconeogenesis)
• β-cells (70%): Insulin → decreases blood glucose (cellular uptake, storage)
• δ-cells (5%): Somatostatin → inhibits insulin/glucagon/GI hormones
• PP-cells (1%): Pancreatic polypeptide → regulates exocrine secretion, appetite
• ε-cells: Ghrelin → hunger stimulation

Key Clinical Entities

• Acute pancreatitis: Gallstones (40%), alcohol (30%), HTG, ERCP, drugs. Ranson/APACHE/BISAP scores.
• Chronic pancreatitis: Recurrent inflammation → fibrosis, calcifications, exocrine/endocrine insufficiency.
• Diabetes mellitus: Type 1 (autoimmune β-cell destruction), Type 2 (insulin resistance + β-cell failure).
• Pancreatic adenocarcinoma: 90% ductal; late presentation, poor prognosis. Risk: smoking, chronic pancreatitis, genetics (BRCA, Lynch).
• Neuroendocrine tumors: Functional (insulinoma, gastrinoma) or non-functional.

Diagnostic Tools

• Lipase/amylase (pancreatitis)
• HbA1c, glucose, C-peptide (diabetes)
• CT/MRI/MRCP/EUS (structural)
• Fecal elastase (exocrine insufficiency)
• CA 19-9 (monitoring, not screening)