The Human Pancreas: Anatomy, Functions & Clinical Significance

The pancreas is a retroperitoneal gland located behind the stomach, spanning the epigastrium and left upper quadrant. It serves dual roles: exocrine (digestive enzyme secretion) and endocrine (hormone production).

Exocrine Function (98-99% of pancreatic mass)

• Acinar cells synthesize and secrete digestive enzymes into the pancreatic duct system.
• Enzymes include: amylase (carbohydrates), lipase (fats), proteases (trypsinogen, chymotrypsinogen – proteins), nucleases (nucleic acids).
• Secreted as inactive zymogens; activated in the duodenum by enterokinase.
• Ductal cells secrete bicarbonate-rich fluid to neutralize acidic chyme, creating optimal pH for enzyme activity.
• Regulated by secretin (bicarbonate) and cholecystokinin/CCK (enzymes) in response to nutrients in the duodenum.

Endocrine Function (1-2% of mass – Islets of Langerhans)

• Beta cells (50-70%): Insulin – lowers blood glucose by promoting cellular uptake, glycogen synthesis, lipogenesis.
• Alpha cells (20-30%): Glucagon – raises blood glucose via glycogenolysis and gluconeogenesis.
• Delta cells (<10%): Somatostatin – inhibits insulin and glucagon secretion.
• PP cells: Pancreatic polypeptide – regulates pancreatic exocrine secretion and appetite.

Clinical Relevance

• Acute pancreatitis: Premature enzyme activation → autodigestion; commonly due to gallstones or alcohol.
• Chronic pancreatitis: Progressive fibrosis → exocrine insufficiency (malabsorption) and endocrine insufficiency (diabetes).
• Diabetes mellitus: Type 1 (autoimmune beta-cell destruction); Type 2 (insulin resistance + relative deficiency).
• Pancreatic neuroendocrine tumors (PNETs): Functional (insulinoma, gastrinoma) or non-functional.
• Pancreatic adenocarcinoma: Aggressive malignancy, often diagnosed late.

Understanding pancreatic physiology is essential for managing diabetes, pancreatitis, and surgical planning.