Pancreas

It lies obliquely across the posterior abdominal wall at about L1 to L2 (transpyloric plane), behind the stomach and lesser sac. The head sits within the C-loop of the duodenum, and the tail extends toward the splenic hilum in the splenorenal ligament.

The parts are the head with the uncinate process, neck, body and tail. The main pancreatic duct (Wirsung) runs the length of the gland and usually joins the common bile duct at the ampulla of Vater, and an accessory duct (Santorini) may open separately at the minor duodenal papilla. Exocrine acini make up most of the gland, with the endocrine islets of Langerhans (about 1 to 2 percent of the mass) scattered throughout, especially in the tail.

The head is supplied by the superior pancreaticoduodenal arteries (from the gastroduodenal artery, coeliac trunk) and the inferior pancreaticoduodenal artery (superior mesenteric artery), forming arcades. The body and tail are supplied mainly by branches of the splenic artery. Veins drain to the splenic and superior mesenteric veins and so to the portal vein.

Parasympathetic fibres from the vagus stimulate exocrine and endocrine secretion, and sympathetic fibres from the splanchnic nerves via the coeliac and superior mesenteric plexuses carry visceral pain afferents. Pancreatic pain is felt in the epigastrium and often radiates to the back.

The exocrine pancreas secretes amylase, lipase, proteases (as inactive precursors such as trypsinogen) and bicarbonate-rich fluid under secretin and cholecystokinin control. The islets secrete insulin (beta cells), glucagon (alpha cells) and somatostatin (delta cells) to regulate blood glucose.

Acute pancreatitis is most often caused by gallstones or alcohol and presents with epigastric pain radiating to the back. Carcinoma of the head of the pancreas typically causes progressive painless obstructive jaundice. Chronic pancreatitis, diabetes mellitus after pancreatic disease, pancreas divisum and annular pancreas are other conditions; management follows local guidelines.

• Retroperitoneal at L1 to L2; parts: head (with uncinate process), neck, body, tail.
• Main duct (Wirsung) joins the common bile duct at the ampulla of Vater; accessory duct (Santorini) at the minor papilla.
• Head: pancreaticoduodenal arcades (coeliac and SMA); body and tail: splenic artery branches.
• Exocrine acini (enzymes, bicarbonate) and endocrine islets of Langerhans (about 1 to 2 percent of mass: insulin, glucagon, somatostatin).
• Carcinoma of the head: painless obstructive jaundice; gallstones and alcohol: main causes of acute pancreatitis.

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2. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. Wolters Kluwer, 8th edition (2018) — Tier 3 (textbook)
3. Sleisenger and Fordtran's Gastrointestinal and Liver Disease. Elsevier, 11th edition (2020) — Tier 3 (textbook)
4. Hall JE, Hall ME. Guyton and Hall Textbook of Medical Physiology. Elsevier, 14th edition (2020) — Tier 3 (textbook)

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