Microscopic anatomy

• Exocrine Pancreas (approx. 85-99% of mass): Composed of acinar cells and a ductal system.
  • Acinar Cells: Synthesize, store, and secrete digestive enzymes (zymogens like trypsinogen, chymotrypsinogen; active enzymes like amylase, lipase). Arranged in clusters (acini).
  • Ductal System: Transports pancreatic juice. Lined by ductal cells that secrete bicarbonate-rich fluid to neutralize gastric acid.
    • Main Pancreatic Duct (Duct of Wirsung): Runs the length of the pancreas from tail to head. Joins the common bile duct to form the hepatopancreatic ampulla (of Vater), which empties into the 2nd part of the duodenum at the major duodenal papilla. Flow controlled by Sphincter of Oddi.
    • Accessory Pancreatic Duct (Duct of Santorini): Variable; when present, typically drains the lower part of the head and empties into the duodenum at the minor duodenal papilla, proximal to the major papilla. May communicate with the main duct.
• Endocrine Pancreas (approx. 1-2% of mass): Consists of Islets of Langerhans, scattered throughout the exocrine tissue (most numerous in the tail). Hormones secreted directly into the bloodstream.
  • Alpha (α) cells (approx. 20%): Secrete glucagon (↑ blood glucose).
  • Beta (β) cells (approx. 75%): Secrete insulin (↓ blood glucose) and C-peptide.
  • Delta (δ) cells (approx. 4-5%): Secrete somatostatin (inhibits insulin, glucagon, growth hormone, and GI hormone secretion).
  • PP cells (F cells): Secrete pancreatic polypeptide (regulates pancreatic secretions).