A C-shaped tube about 25 cm long, the first part of the small bowel, curled around the head of a gland
Duodenum — its name comes from the Latin for 'twelve each', the old length in finger-breadths.
Anatomy · Organs & viscera
Duodenum
First part of the small intestine
Abdomen · gastrointestinal tract
The duodenum is the C-shaped first section of the small intestine, running from the pylorus of the stomach to the duodenojejunal flexure. It wraps around the head of the pancreas and receives bile and pancreatic juice at the major duodenal papilla. It is the shortest, widest and least mobile part of the small intestine and, apart from its first few centimetres, lies behind the peritoneum.
How to spot them
- ▸A C-shaped loop cradling the head of the pancreas, joined to the stomach at the pylorus
- ▸Four parts: superior, descending, horizontal (inferior) and ascending
- ▸Lies mostly retroperitoneally, at about the level of L1 to L3, with the horizontal part crossing in front of the aorta and inferior vena cava
- ▸The bile duct and main pancreatic duct open together into its descending part
What to know
Its second part carries a small raised nipple where the bile duct and the main pancreatic duct open together
The major duodenal papilla (ampulla of Vater) in the duodenum.
A retroperitoneal segment that crosses the aorta and vena cava, trapped beneath the superior mesenteric artery
The third part of the duodenum, compressed in superior mesenteric artery syndrome.
The commonest site of a peptic ulcer, in the first few centimetres after the pylorus
Duodenal ulcers form in the first part, the duodenal cap.
Suspended at its far end by a fibromuscular band from the right crus of the diaphragm, marking the change to the jejunum
The duodenojejunal flexure, held by the suspensory muscle (ligament of Treitz).
Its wall holds mucus-secreting glands that neutralise stomach acid, found nowhere else in the small bowel
Duodenum — Brunner's glands.
The point where the foregut ends and the midgut begins, just below the entry of the bile duct
Duodenum — the foregut-midgut junction lies at the major papilla.
Key ideas
- Acid chyme from the stomach arrives here, is neutralised by bicarbonate, and is mixed with bile and pancreatic enzymes so that fat, protein and starch can be digested.
- Its lining releases the hormones secretin and cholecystokinin, which tell the pancreas and gallbladder to respond.
Quick-fire facts
- •It is about 25 cm (10 inches) long and gets its name from the Latin duodeni, 'twelve each', because of its old length of twelve finger-breadths.
- •Its four parts are the superior (first), descending (second), horizontal or inferior (third) and ascending (fourth).
- •Only the first 2 to 3 cm is intraperitoneal; the rest is retroperitoneal, fixed to the posterior abdominal wall.
- •The head of the pancreas sits in the concavity of the C, and a tumour there can obstruct the duodenum and the bile duct.
- •The major duodenal papilla, in the descending part, receives the common bile duct and main pancreatic duct; a smaller minor papilla lies about 2 cm above it.
- •Blood supply comes from the gastroduodenal and superior pancreaticoduodenal arteries, with the change from coeliac to superior mesenteric supply at the major papilla.
- •The 'duodenal cap' is the first part seen on a barium meal as a triangular shadow.
- •The suspensory ligament of the duodenum is named after the Czech physician Vaclav Treitz.
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