Gross Anatomy
Retroperitoneal mixed gland (~15 cm) from duodenal C-loop to splenic hilum.
Parts
- Head — in C-loop of duodenum; CBD passes through; uncinate process below SMA
- Neck — over SMA/SMV junction
- Body — crosses L2 vertebral column
- Tail — contacts splenic hilum; most mobile
Ducts
- Main duct (Wirsung) — joins CBD at ampulla of Vater; enters D2
- Accessory duct (Santorini) — drains head; opens at minor papilla
| Region | Arterial Supply |
|---|---|
| Head | Superior/inferior pancreaticoduodenal arteries (SMA + celiac) |
| Body/Tail | Splenic artery branches |
Courvoisier sign: painless palpable gallbladder + jaundice = pancreatic HEAD cancer until proven otherwise. Tail cancers are silent until late-stage metastasis.
Exocrine Function
~98% of gland. Acinar cells → enzymes (zymogens); ductal cells → HCO3⁻-rich fluid.
Acinar Cell Products
- Zymogens: Trypsinogen, chymotrypsinogen, proelastase, procarboxypeptidase
- Active: Amylase (digests starch), lipase, phospholipase A2
Activation: Enterokinase (duodenal brush border) → activates trypsinogen → trypsin activates all others.
Regulation: Secretin (S-cells) → HCO3⁻ secretion. CCK (I-cells) → enzyme secretion.
Causes of pancreatitis — GET SMASHED: Gallstones, Ethanol, Trauma, Steroids, Mumps/Autoimmune, Scorpion sting, Hyperlipidemia/Hypercalcemia, ERCP, Drugs. Lipase more specific than amylase for diagnosis.
Endocrine Function & Islets
Islets of Langerhans (~1-2% of gland; concentrated in tail). Drain into portal circulation.
| Cell | % Islet | Hormone | Stimulus |
|---|---|---|---|
| Beta (B) | ~65%; center | Insulin, C-peptide, Amylin | High glucose, GLP-1, amino acids |
| Alpha (A) | ~20%; periphery | Glucagon | Low glucose, stress |
| Delta (D) | ~10% | Somatostatin | High glucose/AA/fat |
| PP cells | ~5% | Pancreatic polypeptide | Fasting, vagal stimulation |
C-peptide distinguishes endogenous (HIGH) vs exogenous insulin (LOW). Insulinoma = high insulin + HIGH C-peptide. Factitious hypoglycemia (self-injection) = high insulin + LOW C-peptide.
Islet layout — "DAB" outside-in: Delta (periphery), Alpha (periphery), Beta (center). Beta cells are in the center like a Bear in a cave.
Embryology
Two endodermal buds from the foregut fuse at week 7:
- Dorsal bud → body, tail, superior head (Santorini duct)
- Ventral bud (rotates with bile duct) → uncinate + inferior head (Wirsung duct)
Annular pancreas: ventral bud fails to rotate → ring around duodenum → double-bubble sign in neonates. Pancreas divisum: ducts fail to fuse → most common congenital pancreatic anomaly → chronic pancreatitis risk.
Clinical Pearls
| Condition | Key Features | Lab Clue |
|---|---|---|
| Acute pancreatitis | Epigastric → back pain; Cullen/Grey Turner signs | ↑↑Lipase (specific), ↑Amylase |
| Chronic pancreatitis | Steatorrhea, DM, calcifications; alcohol/CF | ↓Fecal elastase; ↑fecal fat |
| Pancreatic adenocarcinoma | Courvoisier; Virchow node; Trousseau syndrome | ↑CA 19-9 |
| Insulinoma | Whipple triad: hypoglycemia + neuro sx + glucose relief | ↑Insulin, ↑C-peptide |
| Glucagonoma | Necrolytic migratory erythema, DM, weight loss | ↑Glucagon |
| VIPoma | Watery Diarrhea, Hypokalemia, Achlorhydria (WDHA) | ↑VIP |