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Anatomy of the Pancreas

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AMA
MD A.. Anatomy of the Pancreas. My Endo Consult. Published January 11, 2025. Accessed October 18, 2026. https://myendoconsult.com/learn/topics/anatomy-of-the-pancreas/
APA
MD A. (2025). Anatomy of the Pancreas. My Endo Consult. https://myendoconsult.com/learn/topics/anatomy-of-the-pancreas/
Vancouver
MD A.. Anatomy of the Pancreas [Internet]. My Endo Consult; January 11, 2025 [cited October 18, 2026]. Available from: https://myendoconsult.com/learn/topics/anatomy-of-the-pancreas/
BibTeX
@online{myendoconsult4422471,
  author = {Akuffo Quarde, MD},
  title  = {Anatomy of the Pancreas},
  organization = {My Endo Consult},
  year   = {2025},
  url    = {https://myendoconsult.com/learn/topics/anatomy-of-the-pancreas/},
  urldate = {October 18, 2026}
}

PANCREAS ANATOMY AND HISTOLOGY

Gross Anatomy

  1. Location and Position
    • Retroperitoneal organ, 15–20 cm long, 75–100 g weight.
    • Oblique position: from duodenum (right) to splenic hilum (left).
    • Four Regions: head, neck, body, tail.
    • Head: resides in C-loop of duodenum, anterior to vena cava, right renal artery, both renal veins.
      • Uncinate process = posteromedial aspect, behind portal vein & SMA/SMV.
    • Neck: anterior to portal vein, at L1–L2 level.
    • Body: extends anterior to aorta (origin of SMA).
    • Tail: left end, near spleen, anterior to left kidney, over splenic hilum.
  2. Peritoneal Cover
    • Anterior surface covered by peritoneum.
    • Base of transverse mesocolon attaches to inferior margin of body/tail.
location of the pancreas

Embryologic Origin

  1. Fusion of Ventral & Dorsal Buds
    • Ventral bud → duct of Wirsung (main pancreatic duct), becomes inferior portion of head + uncinate process.
    • Dorsal bud → duct of Santorini (accessory), becomes body & tail.
  2. Duct Anatomy
    • Main duct (Wirsung) joins common bile duct → ampulla of Vater → empties into duodenum (2nd part).
    • Sphincter of Oddi controls flow of bile & pancreatic juice at ampulla of Vater.

Blood Supply and Drainage

  1. Arteries
    • Branches from celiac trunk (via splenic artery & common hepatic/gastroduodenal) and SMA.
    • Head & Uncinate: gastroduodenal artery branches, SMA branches.
    • Body & Tail: branches of splenic artery & inferior pancreatic artery (from SMA) → form arterial arcades.
  2. Veins
    • Head region: anterior & posterior venous arcs → drain to portal & mesenteric veins.
    • Body & Tail: venous outflow → splenic vein → portal system.
  3. Lymphatics
    • Dense lymphatic network draining to local/peripancreatic LNs.

Innervation

  1. Sympathetic & Parasympathetic
    • Innervate acinar (exocrine) cells, islet (endocrine) cells, vasculature.
    • Parasympathetic → stimulates secretions (endo & exo).
    • Sympathetic → generally inhibitory.
  2. Neurotransmitters & Peptides
    • Peptides/ amines (somatostatin, galanin, VIP, CGRP) released by pancreatic nerves.
    • Afferent sensory fibers → explain severe pain in pancreatitis.

Histologic Components

  1. Tissue Distribution
    • ~85% exocrine, 2% endocrine, 10% extracellular matrix, 3–4% vessels & ducts.
  2. Exocrine Portion
    • Acinar cells in clusters/lobules → secrete digestive enzymes into ducts → main pancreatic duct → duodenum.
    • Acinar cells: abundant RER, apical zymogen granules.
  3. Endocrine Portion (Islets of Langerhans)
    • Scattered small clusters in the acini.
    • 3 main cell types:
      • β-cells (75%) → insulin
      • α-cells (20%) → glucagon
      • δ-cells (5%) → somatostatin
    • Other islet cells: δ2-cells (VIP), PP-cells (pancreatic polypeptide).
Histology of the Pancreas

EXOCRINE FUNCTIONS OF THE PANCREAS

  1. Pancreatic Juice
    • ~1 L/day, alkaline, isosmotic, rich in HCO₃⁻ & proteins.
    • Functions: neutralize gastric acid in duodenum & digest macronutrients.
  2. Digestive Enzymes
    • Amylase: degrades starch, glycogen → maltose, dextrins.
    • Proteases (secreted as proenzymes): trypsinogen (→ trypsin by duodenal enterokinase), chymotrypsinogen, elastase, carboxypeptidases → degrade proteins to peptides/amino acids.
      • Pancreatic secretory trypsin inhibitor prevents autoproteolysis.
    • Lipolytic Enzymes: lipase, phospholipase A2, etc. → break down fats into FAs, glycerol, micelles.
  3. Acinar Architecture
    • ~40 acinar cells/acinus, plus centroacinar cells at center near duct origin → secrete electrolytes, bicarbonate.
  4. Regulation of Secretion
    • Basal rate ~2% of max; Meal-stimulated phases:
      • Cephalic (10%): via sight/smell of food, mediated by cholinergic input.
      • Gastric (10%): distention → gastrin + vagal reflex → moderate enzyme/bicarbonate secretion.
      • Intestinal (80%): acid/fat/protein in duodenum → secretin (↑ HCO₃⁻ secretion), CCK (enzyme secretion), synergy for maximum output.

NORMAL HISTOLOGY OF PANCREATIC ISLETS

  1. Islet Distribution & Size
    • ~1 million islets, mostly in tail region. Size 40–300 µm.
    • Each islet ~3000 cells; total islet mass ~1 g.
  2. Cell Types & Arrangement
    • β-cells: 75%, central in islet, produce insulin (Ponceau/Gomori stain: bluish-purple granules).
    • α-cells: 20%, peripheral in islet, produce glucagon (stain pink/red).
    • δ-cells: 5%, smaller, produce somatostatin.
    • PP-cells: produce pancreatic polypeptide (mainly in head).
  3. Insulin
    • 56–AA peptide (two chains + disulfide bonds), discovered in 1920.
    • Regulated by plasma glucose, neural signals, paracrine factors.
    • Enhances glucose uptake, glycogen storage, protein synthesis; inhibits gluconeogenesis, lipolysis, ketogenesis.
  4. Glucagon
    • 29–AA single chain, antagonizes insulin, promotes hepatic glycogenolysis & gluconeogenesis.
    • Inhibited by high glucose, GLP-1, insulin, somatostatin.
  5. Somatostatin
    • 14 or 28–AA forms, generally inhibits hormone secretion (insulin, glucagon, GH, etc.).
  6. Pancreatic Polypeptide (PP)
    • 36–AA hormone, inhibits gallbladder contraction, bile & pancreatic exocrine secretions; modulates insulin receptor.
  7. Amylin (IAPP)
    • 37–AA co-secreted w/ insulin.
    • Slows gastric emptying, inhibits digestive secretions, suppresses glucagon release.

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