Duodenum

Function

The duodenum — 'twelve fingers' breadth' — is the gut's chemical mixing chamber, a C-shaped 25 cm loop cradling the pancreatic head. Its descending limb carries the ampulla of Vater, where bile and pancreatic juice spray into the lumen, and its walls host Brunner's alkaline-mucus glands that neutralise gastric acid.

Here the critical digestion happens: pancreatic amylase, lipase and proteases meet their substrates, bile salts emulsify fat, and iron and calcium absorption begins. The duodenal hormones — secretin, cholecystokinin — command the pancreas and gallbladder like endocrine generals.

Blood supply

Gastroduodenal and superior mesenteric arcades; the pancreaticoduodenal anastomosis joins foregut and midgut supply.

Nerve supply

Vagus and coeliac plexus; enteric nervous system.

Clinical relevance

Duodenal ulcer

Posterior duodenal ulcers bleed from the gastroduodenal artery or perforate into the retroperitoneum — pain radiating to the back.

Superior mesenteric artery syndrome

After rapid weight loss the SMA's angle with the aorta can narrow and compress the duodenum's third part.

Related conditions

• Peptic ulcer disease
• Coeliac disease