THE DUODENUM

Location and position  
  • Epigastric region:

  • Extends a little into the right hypochondrium and right lumbar.

  • Joins the pylorus of the stomach to the jejunum

  • Moulded around the head of the pancreas.
  • Mostly retroperitoneal, from L1 –l3.
   
Parts  
  • Superior (first part), anteriolateral to the body of L1.
  • Descending (second part) to the right of L1, L2 and L3.
  • Horizontal (third part) anterior to L3.
  • Ascending (fourth part) to the left of the body of L3.

These parts have different relations, mentioned below:

   
Superior part  

Its proximal part has a mesentery. The greater omentum and hepatoduodenal ligament are attached to it - It is free to move.

   

Relations

Anterior relations Posterior Superior Inferior
  • Peritoneum
  • Gall bladder
  • Quadrate lobe of the liver
  • Bile duct
  • Portal vein
  • Inferior vena cava
  • Gastroduodenal artery
  • Neck of gall bladder
  • Pancreas
   
Descending part :
  1. Retroperitoneal
  2. Parallel and to the right of inferior vena cava.
   

 

Anterior Posterior Medial
  • Transverse colon
  • Transverse mesocolon
  • Some coils of jejunum
  • Hilum of right kidney
  • Renal vessels
  • Ureter
  • Psoas major muscle
  • Head of pancreas
  • Pancreatic duct
  • Bile duct

 
   
Horizontal part :

Retroperitoneal and adherent to the posterior abdominal wall.

 

Posterior relations: Superior relations:
  • Right psoas major muscle
  • Inferior vena cava
  • Aorta
  • Right ureter
  • Pancreas
  • Superior mesenteric vessels.
   
Ascending part :
  • Its distal end is covered by peritoneum, and is movable.
  • Most of it is retroperitoneal and adherent to the posterior abdominal wall.
  • Ascends to the left of the aorta to L2.
Anterior relations Posterior relations: Medially:
  • Root of mesentery and coils of jejunum.
  • Left psoas major muscle
  • Left margin of aorta.
  • Head of pancreas
  • At its termination, the ascending part of the duodenum becomes continuous with the jejunum at the duodenojejunal junction.

  • The duodenojejunal flexure is supported by a fibro muscular band called the suspensory ligament (muscle) of the duodenum.

  • This ligament connects the duodenum, and the duodenojejunal flexure to the right crus of the diaphragm close to the esophagus opening.

This structure serves two functions

•  supports the duodenojejunal flexure

•  widens the angle of the flexure, thereby facilitating movement of its contents.

 

 

 
Peritoneal relations of duodenum  
  • The initial and terminal parts of the duodenum are covered by peritoneum

  • The superior part of the duodenum is attached to the liver by the hepatoduodenal ligament.

The rest of the duodenum is retroperitoneal.

The recesses associated with the duodenojejunal junction include;

  • Superior duodenal recess

  • Inferior duodenal recess

  • Retroduodenal recess

  • Paradeudenal recess. .

These recesses are potential sites of internal hernia.

   

Blood supply

  • Dual blood supply.

  • Proximal half: Gastro- duodenal artery from common hepatic

  • Second half: Duodenal branches of the superior mesenteric, pancreatico-duodenal branches of the superior mesenteric.

  • The veins correspond and drain to the superior mesenteric and portal veins

 

Lymphatic drainage

  • Pancreatico duodenal lymph nodes

  • Celiac lymph nodes

  • Superior mesenteric nodes

Innervation

  • Vagus

  • Greater splanchnic through celiac plexus
Retroperitoneal organs