Duodenum

• The duodenum is the first part of the small intestine
• It has no mesentery.
• It is about 25 cm long.
• Duodenum forms a C-loop around the head of the pancreas. 
• It is divided into four parts
  • The first part
    • From pylorus to Gall bladder neck
    • is encased in the hepatoduodenal ligament
    • Measures 5 cm
  • The second part
    • From neck of Gall bladder to L3
    • Descending part
    • 8-10 cm long
    • It is a retroperitoneal structure.
    • Contains the ampulla, into which the pancreatic duct and common bile duct drain. 
  • The third part 
    • Transverse part 
    • Extends from L3 across left and upwards
    • About  10 cm in length.
  • The fourth part
    • Continues as jejunum at L2
    • Held in place by the ligament of Treitz. 
    • This ligament connects the duodenum to the right crus of the diaphragm.

1st part duodenum

• Relationship
  • Above and anterior
    • Quadrate lobe of liver
    • Gall bladder
  • Behind
    • Gastrodudenal artery
    • Bile duct and portal vein
    • Head and neck of pancreas

2nd part duodenum 

• Anterior
  • Liver
  • Transverse colon
  • Jejunum
• Posterior
  • Right kidney
  • Right renal vein
  • IVC
  • Psoas
• Mediallly
  • Head of pancreas
  • Bile duct
  • pancreatic duct
• Lateral
  • Right colic flexure

3rd part of duodenum

• Anterior
  • SMA
  • SMV
• Posterior
  • Right ureter
  • Psoas
  • IVC
  • Abdominal aorta
• Upper
  • Pancreas
• Lower
  • Jejunum

4th part of duodenum

• Right
  • Aorta
• Left
  • Left Ureter
  • Left kidney
• Above
  • Body of pancreas
• Anterior
  • Transverse colon
  • Mesocolon

Applied Anatomy