The duodenum is the first and shortest section of the small intestine, divided into four parts with specific lengths and relations to surrounding organs. It plays a critical role in digestion and is prone to certain medical conditions such as peptic ulcers. Its structure includes serosa, muscularis externa, submucosa, and mucosa, with detailed blood supply and nerve innervation described in the document.

1. DUODENUM

2. INTRODUCTION
• First, Shortest, widest, and most
fixed part of small intestine
• Do-deka-dactulos -12 fingers
breadth
• Length = combined width of 12
fingers
• Mostly retroperitoneal (except
1st
part)
• C shaped, encloses the head of
the pancreas
• Location :- epigastric and
umbilical region

3. Subdivided into four parts
• First or upper part –2inches/ 5cm
• Second or vertical part –3inches/ 7.5cm
• Third or horizontal part –4inches/10cm
• Fourth or ascending part – 1inch/ 2.5cm

4. First part of duodenum
• Extension –pylorus to superior
duodenal flexure
• Direction –upwards, backwards
and to the right
• Length -5cm or 2inches
• Features
- Most movable, partly
retroperitoneal
- Develops from foregut
- Supplied by end arteries
- Devoid of circular mucous fold

5. • Relations :
- Anteriorly – covered with
peritoneum of the greater sac,
and is related to
i. Quadrate lobe of liver
ii. Neck and body of gall
bladder
- Posteriorly –non-peritoneal
related to
i. Portal vein,
ii. Bile duct,
iii. Gastroduodenal artery,
iv. IVC

6. Relations
• Superiorly –forms floor of
epiploic foramen and
related to hepatic artery
• Inferiorly –head and neck of
pancreas

7. Second part of duodenum
• Extension –from superior
duodenal flexure to
inferior duodenal flexure
• Upper ½ develops from
foregut & lower ½ from
midgut.
• Direction –downward in
front of hilum of kidney
• Length –3inches or 7.5cm

8. • Relations :
- Anteriorly –
i. Rt lobe of liver
ii. Fundus and body of gall
bladder
iii. Transverse colon

9. - Posteriorly –
i. Rt kidney, Rt renal
vessels, pelvis of Rt
ureter
ii. Rt psoas major muscle
iii. Rt edge of IVC

10. - Laterally –
Rt colic flexure
- Medially-
i. Head of pancreas
ii. Anastomosis of Superior and
inferior pancreatico-
duodenal vessels
iii. Bile duct and pancreatic duct
–unite to form ampulla of
Vater

12. Interior of second part of duodenum
• Circular folds (plicae circularis) –permanent mucous folds
• Major duodenal papilla –conical projection arising from
posteromedial wall, situated 8-10cm distal to pylorus
• Minor duodenal papilla –small conical projection situated 2cm above,
opening of accessory pancreatic duct

13. Interior of second part of duodenum
• Plica semicircularis –forms an arch over Major duodenal papilla,
resemble monk’s hood
• Plica longitudinalis –vertical fold extending from major papilla

14. Third part of duodenum
• Extension –from inferior
duodenal flexure to front of
aorta
• Length – 4 inches or 10 cm

15. • Relations :
- Anteriorly –crossed by
superior mesenteric vessels,
root of mesentery
- Posteriorly –non-peritoneal
and related to
1. Rt psoas major,
2. Rt ureter,
3. IVC,
4. Rt gonadal vessels,
5. abdominal aorta

16. Relations
- Superiorly –head of
pancreas, inferior
pancreaticoduodenal
vessels
- Inferiorly –coils of jejunum

17. Fourth part of duodenum
• Extension –from front of
aorta to DJ flexure
• Length –1 inch or 2.5cm
• Flexure is kept in position by
suspensory muscle of
duodenum

18. • Relations :
- Anteriorly –covered with
peritoneum, related to
transverse colon and
mesocolon
- Posteriorly –Lt crus of
diaphragm, Lt psoas major, Lt
sympathetic trunk, Lt gonadal
vessels, Lt suprarenal vein,
inferior mesenteric vein
- Rt side –uncinate process
- Lt side –Lt kidney, ureter
- Above –body of pancreas

19. Suspensory muscle of duodenum
OR
Suspensory ligament of treitz
• Fibro-muscular band arises
from Rt crus of diaphragm
• Passes downward and
forward by side of coeliac
artery
• The band is attached to
posterior surface of DJ flexure
• Upper 1/3 –striated muscle
middle 1/3 –elastic fibres
lower 1/3 –nonstriated
muscle

20. • Function –flexes Dj flexure
and prevent it from being
dragged down
- Landmark in radiological
diagnosis of incomplete
rotation or mal rotation of
small intestine

21. Structure of duodenum
• Serosa –derived from
peritoneum, incomplete
• Muscularis externa –outer
longitudinal, inner circular
separated by myenteric
plexus of nerves
• Submucosa –loose areolar
tissue contain plexus of blood
vessels, lymphatics, meissner’s
plexus, Brunner’s gland
• Mucosa –surface epithelium,
lamina propria, muscularis
mucosa

22. ENDOSCOPIC APPEARANCE
A) 1ST
part
B) 2nd
part
C) Major duodenal
papilla
D) 3rd
part

23. Blood supply of duodenum
• Superior pancreaticoduodenal artery
• Inferior pancreaticoduodenal artery
• Supraduodenal artery of Wilkie br of Gastroduodenal art
• Retroduodenal branch of gastroduodenal artery
• Leash of branches of hepatic artery
• Branches from Rt gastroepiploic artery
• Artery from first jejunal branch of SMA

24. Venous drainage
• Veins corresponding to
arteries drain into SMV
and portal vein

25. Lymphatic drainage
• Pancreaticoduodenal lymph
nodes
• coeliac and superior
mesenteric groups of pre-
aortic lymph nodes

26. Nerve supply
• Sympathetic – from T6-T9
• Parasympathetic –from
both vagi through celiac
and superior mesenteric
plexus

27. Applied
• First part of duodenum –prone
to peptic ulcer, supplied by
series of end arteries
1. Mucosal folds are absent
2. Acidic contents of stomach
enters
- Causes –trauma, alcohol,
smoking, ulcerogenic drugs
(NSAID)
- Sometimes gastroduodenal
artery passing behind first part
and get erroded by peptic ulcer,
producing severe haemorrhage

28. Duodenal cap
• Devoid of circular folds in
the 1st
part of duodenum
• seen as duodenal cap in
barium meal radiographs
of abdomen
• Presents a triangular
shadow having a well
demarcated base and
less distinct apex
duodenal cap/ bulb.

29. • Second part –more
protected, opening of bile
duct and pancreatic duct
• Small bile stones impacted on
summit of major duodenal
papilla –obstructive jaundice
• Annular type of head of
pancreas –encircles the
duodenum – malignant
growth of pancreatic head –
duodenal obstruction

30. • Third part of
duodenum – more
prone to external injury
as it may compressed
between vertebral
column & AAW
following violence.

31. • Duodenal recess
- Superior –bounded in
front by superior duodenal
fold
- Inferior –bounded in front
by inferior duodenal fold
- Retroduodenal –behind
junction of 3rd
and 4th
part
- Paraduodenal –anteriorly
bounded by paraduodenal
fold contain inferior
mesenteric vein

32. • A loop of small gut may herniate into any of
the recess
• If the gut fails to return, the internal hernia
thus formed produces intestinal obstruction