First segment of the small intestine, 23-28 cm in length.

Smallest segment of the small intestine.

Almost all retroperitoneal

Curves down and then up from the pylorus of the stomach.

It receives partially digested food, chyme, from the stomach.

Receives gall bladder and pancreatic secretions to help in digestion and to neutralize acid stomach contents.

Nutrient absorption begins in the lower duodenum.

Excessive acidity leads to peptic ulcer disease.

Lined with cells that secrete alkaline fluids and enzymes.

Highly folded mucosal surface for absorption of nutrients.

Brunner’s glands found in the duodenum secrete mucous.

Bruner glands produce alkaline mucin secretions protecting the epithelium from gastric chyme.

Bruner gland tumor is a rare benign duodenal lesion with an estimated incidence of 0.008% based on autopsy studies.

Bruner gland tumor is a hamartomatous lesion, with no known potential for malignant transformation.

Bruner gland tumor typically is found incidentally on endoscopy.

Terminates at the duodenaljejunal flexure, at the ligament of Treitz.

Divided into 4 sections: the first part is a continuation of the duodenal end of the pylorus, it is peritoneal and passes to the right, superiorly and posteriorly, for approximately 5 cm, before curving inferiorly into the superior duodenal flexure.

The second part of the duodenum begins at the superior duodenal flexure ans passes inferiorly to the lower border of L3, where it severely turns medially into the inferior duodenal flexure,it is the site of entry of the pancreatic duct and the common bile duct via the pancreatic duct. The pancreatic duct enters through the duodenal papilla , the ampulla of Vater. The second part also contains a minor duodenal papilla, which provides access for the accessory pancreatic duct.

The third part of the duodenum begins at the inferior duodenal flexure and passes to the left crossing the right ureter, right ovarian/testicular vessels, the inferior vena cava, abdominal aorta, superior mesenteric artery and the vertebral column.

The fourth part of the duodenum passes the aorta until it reaches the inferior border of the pancreas, when it curves anteriorly and ends at the duodenojejunal flexure. The duodenojejunal flexure is surrounded by peritoneal muscle fibers, the ligament of Treitz.

Receives blood supply from 2 sources: in the proximal two parts of the duodenum the gastroduodenal artery and its branch the superior pancreaticoduodenal artery, the third and fourth parts of the duodenum receive their blood from the superior mesenteric artery and its branch the inferior pancreaticoduodenal artery.

The superior and inferior pancreaticoduodenal ateries from two different arteries form an anastomotic loop and provide collateral blood to the duodenum.

The venous drainage of the duodenum follows the arterial circulation and drains into the portal system via the splenic or superior mesenteric vein.

Lymphatic vessels anteriorly drain into the pancreatoduodenal lymph nodes along the superior and inferior pancreatoduodenal arteries and then into the pyloric lymph nodes, and the posterior lymph vessels pass the head of the pancreas and drain into the superior mesenteric lymph nodes.

Most fixed part of the small intestine.

Helps to regulate the emptying rate of the stomach via hormones secretin and cholecystokinin which are released from duodenal epithelial cells in response to acidic and fatty stimuli from gastric chyme.

Duodenal hormones also cause the liver and gallbladder to release bile and the pancreas to release bicarbonate and digestive enzymes trypsin, lipase and amylase into the duodenum.

Well protected from abdominal injuries due to its location in the retroperitoneal space.

The second part of the duodenum shares its blood supply with the pancreas

Injuries occur in 3-5% of patients who sustain abdominal trauma.

Approximately 75-85% of duodenal injuries result from firearms and stab wounds.

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