Abdominal Anatomy for MRCEM PRIMARY EXAM

12/24/2025 1
London Global EM Programme, Director Dr Ash (Consultant Emergency Medicine, Acute Medicine & Geriatric Medicine
NHS UK)
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Topic:
Name of Presenter: DR MUHAMMAD AZEEM IMRAN
Date of Presentation: SEP 23,2023
LGEM Programme: UNDER KIND SUPERVISION OF DR ASHFAQ AHMED SORATHIA
ABOMINAL ANATOMY FOR EM AND ACUTE PHYSICIANS SESSION 1

12/24/2025 2
London Global EM Programme, Director Dr Ash (Consultant Emergency Medicine, Acute Medicine & Geriatric Medicine
NHS UK)
info@londongem.uk
LEARNING OBJECTIVES
THE GASTROINTESTINAL TRACT
THE ACCESSORY ORGANS OF THE ABDOMEN
VASCULATURE OF THE ABDOMEN

THE GASTROINTESTINAL TRACT
London Global EM Programme, Director Dr Ash
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• The oesophagus is a fibromuscular tube, approximately 25cm in length, that transports food from the pharynx to the
stomach.
• It originates at the inferior border of the cricoid cartilage (C6) and extends to the cardiac orifice of the stomach (T11)
THE OESOPHAGUS
Anatomical Course
• The oesophagus begins in the neck, at the level of C6. Here, it is continuous superiorly with the laryngeal part of the pharynx (the
laryngopharynx).
• It descends downward into the superior mediastinum of the thorax, positioned between the trachea and the vertebral bodies of T1 to
T4. It then enters the abdomen via the oesophageal hiatus (an opening in the right crus of the diaphragm) at T10.
• The abdominal portion of the oesophagus is approximately 1.25cm long – it terminates by joining the cardiac orifice of
the stomach at level of T11.
Anatomical Relations
The anatomical relations of the oesophagus give rise to four physiological constrictions in its lumen – it is these
areas where food/foreign objects are most likely to become impacted. They can be remembered using the
acronym ‘ABCD‘:
•Arch of aorta
•Bronchus (left main stem)
•Cricoid cartilage
•Diaphragmatic hiatus

Arterial Supply
• The rich arterial supply of oesophagus is
segmental.
1. Branches of inferior thyroid artery, a branch of thyrocervical trunk of
subclavian artery
UES and
cervical part
2. Paired aortic oesophageal arteries Thoracic part
3. Left gastric artery and a branch of left inferior phrenic
artery
LES and the
most distal oesophagus
1. Veins from the cervical part drain into the inferior thyroid veins.
2. The thoracic part is drained by veins that flow into the azygos and
hemiazygos venous systems, as well as into the intercostal and
bronchial veins.
3. The vessels from the abdominal part open into the left and short
gastric veins.
Venous Drainage
Nerve
Supply
Parasympathetic nerve supply(Sensory,Motor,Secretomotor)
• Upper1/2 Recurrent Laryngeal Nerve
• Lower 1/2 Esophageal plexus formed by the 2 vagus plexus
Sympathetic nerve supply(Vasomotor)
• Upper1/2
• Lower 1/2
By fibers from mid cervical ganglion
From upper 4 thoracic ganglia
THE OESOPHAGUS

Lymphatics
The lymphatic drainage of the oesophagus is divided into thirds:
•Superior third – deep cervical lymph nodes.
•Middle third – superior and posterior mediastinal nodes.
•Lower third – left gastric and celiac nodes.
THE OESOPHAGUS
Clinical Relevance: Disorders of the Oesophagus
Barrett’s Oesophagus
Barrett’s oesophagus refers to the metaplasia (reversible change from one differentiated cell type to another) of lower oesophageal
squamous epithelium to gastric columnar epithelium. It is usually caused by chronic acid exposure as a result of a malfunctioning lower
oesophageal sphincter. The acid irritates the oesophageal epithelium, leading to a metaplastic change.
The most common symptom is a long-term burning sensation of indigestion.
It can be detected via endoscopy of the oesophagus. Patients who are found to have it will be monitored for any cancerous changes.
Oesophageal Varices
The abdominal oesophagus drains into both the systemic and portal circulation, forming an anastomosis between the two.
Oesophageal varices are abnormally dilated sub-mucosal veins (in the wall of the oesophagus) that lie within this anastomosis. They are
usually produced when the pressure in the portal system increases beyond normal, a state known as portal hypertension. Portal
hypertension most commonly occurs secondary to chronic liver disease, such as cirrhosis or an obstruction in the portal vein.
The varices are predisposed to bleeding, with most patients presenting with haematemesis (vomiting of blood). Alcoholics are at a high
risk of developing oesophageal varices.
Oesophageal Carcinoma
Around 2% of malignancies in the UK are oesophageal carcinomas. The clinical features of this carcinoma are:
•Dysphagia – difficulty swallowing. It becomes progressively worse over time as the tumour increases in size, restricting the
passage of food.
•Weight loss
There are two major types of oesophageal carcinomas: squamous cell carcinoma and adenocarcinoma.
•Squamous cell carcinoma – the most common subtype of oesophagus cancer. It can occur at any level of the oesophagus.
•Adenocarcinoma – only occurs in the inferior third of the oesophagus and is associated with Barrett’s oesophagus. It
usually originates in the metaplastic epithelium of Barrett’s oesophagus

Introductio
n
London Global EM Programme, Director Dr Ash (Consultant Emergency Medicine, Acute Medicine & Geriatric Medicine NHS UK)
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• It in the widest and most distensible part of alimentary canal between the esophagus and the
duodenum .
• Functions of stomach are :
(a) Forms a reservoir of food .
(b) Mixes food with gastric secretions to form chyme .
(c) Controls rate of delivery of chyme
(d) HCL destroys bacteria
(e) Intrinsic factor present in gastric juice helps in absorption of vitB12 in small intestine .
Locatio
n
• Situated in upper left part of abdomen occupying left hypochondriac , umbilical and Epigastric
regions -
THE STOMACH

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• It extends obliquely from left hypochondriac to run. epigastric region.
(a) Reversed L shaped
(b) I shaped
(c) Semi Lunar
(d) steer - Horn .
Size & Capacity
• Length - 10 inches
• Capacity
• (a) At birth - 30mL
• (b) At puberty - 1000 mL
• (c) In adults = 1.5 to 2 L
Shape
• It in mostly J shaped .
• Can differ
THE STOMACH

THE STOMACH
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(a) Two ends : cardiac & Pyloric
(b) Two curvatures : Greater & lesser
(c) Two surfaces : Anterior ( Ant. superior ) and Posterior ( post . inferior)
• Cardiac part (or cordial)
• Fundus
• Body
• Pyloric Part
External features
• It presents following external features :
• The cardiac end of stomach in less mobile and less likely to vary
position whereas pyloric end of stomach in more mobile .
Part
s
--- Pyloric Antrum --- Pyloric canal ----
pylorus

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Relations
• The stomach well covered by the peritoneum except where blood vessels run along its curvature
and a small area [Bare Area] posteriorly near the cardiac orifice .
• Peritoneal folds extending from lesser & greater curvatures of stomach to other structures are
as follows :
• (1) Lesser Omentum, extends from lesser curvature
of stomach to liver
• (2) Greater omentum extends from lower 2/3rd
greater curvature to transverse colon .
• (3) Gastrosplenic ligament extends from the upper
one - third (fundus) to spleen .
• (4) Gastrophrenic ligament extends to Diaphragm .
THE STOMACH

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Visceral Relations
• (1) Anterior ( Anterosuperior surface)
• Relations of posterior ( Postero Inferior) Surface [Stomach Bed]
(a) Diaphragm
(b) left kidney
(c) left suprarenal gland
(d) Pancreas
(e) Transverse colon .
(f) left colic flexure
(g) splenic artery .
(h) Spleen
THE STOMACH

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Arterial Supply
• Left gastric Artery [ Coeliac trunk]
• Right gastric Artery [ Common hepatic A]
• Left Gastroepiploic A . [ Splenic A. ]
• Right Gastro epiploic A. Gastroduodenal A.
• Short gastric A. (splenic A.) (5 - 7 in number)
Venous drainage
• left & Right Gastric Vein
• left & Right Gastroepiploic V
• Short gastric V
Lymphatic Drainage
• Divided into 4 areas in with various Nodes .
THE STOMACH

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Nerve Supply
• Supplied by both sympathetic & Parasympathetic .
• Derived from T6 to T10 via Greater splanchnic Nerves , Coeliac and Hepatic plexuses .
Parasympatheti
c
• Directly from Vagus N .
• Supply to stomach
in
(a) Vasomotor
(b) Motor to pyloric sphincter
(c) Inhibitory to Remaining Gastric muscles
(d) Chief pathway for pain in stomach
THE STOMACH
Sympathetic

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• Hepatic branch
• Coeliac branch
• Gastric branch Nerve of latarjet
• Coeliac branch
• Nerve of Grassi
• Gastric Branch .
• Branches of Posterior Vagal Trunk:
• Branches of Ant Vagal Trunk :
THE STOMACH

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Applied Anatomy

Introductio
n
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Small Intestine
• Anatomically the small intestine extends from the pylorus to the ileocaecal junction .
Duodenum = 25cm
Jejunum = 2. 5 m
ileum =3 m
Jejunum & ileum
.
• It is about ~ 6 m
• Duodenum is Retroperitoneal and fixed .
• The small intestine proper extends from the duodeno-jejunal
flexure to ileocaecal junction .

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• Jejunum - - 2/5th and ileum = 3/5 th .
• Both are suspended from posterior abdominal wall by a large fold of peritoneum called
Mesentery of small intestine .
• The wall of small intestine consists of four layers : -
(a) Mucosa
(b) Sub mucosa
(c) Muscle layer
(d) Serosa .
Mucos
a• Three relevant features
(a) larger Surface Area by Plicae circulars , villi and microvilli
(b) Instestinal Glands ( crypts of lieber Kauhn )
(c) Lymphatic follicles - [ solitary lymph follicles _Aggregated lymph follicles .
(Peyer's Patches)
Small Intestine

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Submucosa
• Made up of loose areolar tissue and contains blood vessels , lymph
vessels and nerve plexus ( Meissner's plexus )
Muscle layer
• It is made up of outer longitudinal and inner circular layers of smooth
muscle.
• Auerbach 's plexus of nerves in present in between these two layer ?
Serosa
• It is formed by the visceral peritoneum and in lined by simple squamous
epithelium -
Arterial
supply
• Jejunum and ileum are supplied by the jejunal and ileal branches of superior mesenteric
artery .
( 12 - 15 in number)
Small Intestine

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• Terminal Part of ileum = Ileal branches of ileocolic branch of superior
mesenteric artery .
• As soon as these enter the mesentery they break up into smaller
branches which form Arterial arcades .
• From convene ' ties of terminal arcades , small parallel straight vessels
called Vasa recta arise .
Venous - Drainage
• It is formed by the visceral peritoneum and in lined by
simple
squamous epithelium -
Small Intestine

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Lymphatic
drainage
• Drain into Superior mesenteric nodes present around the
origin of superior mesenteric artery .
Nerve Supply :
• The small intestine we supplied by both
sympathetic & parasympathetic nerve
fibres
• Sympathetic supply from Tio - Tn spinal
segments through splanchnic nerves and
superior mesenteric plexus .
• Pain from jejunum and ileum in referred
to umbilical region.
Small Intestine

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• Parasympathetic supply is derived from the vagus nerves through the
coeliac and superior mesenteric plexuses -
• The sympathetic fibres are motor to the gut sphincters whereas the
parasympathetic fibres stimulate the peristalsis and are inhibitory to the
sphincters .
Mesentery of small
Intestine
• It forms broad fan - shaped fold of peritoneum , which suspends the
small intestine from the posterior abdominal wall .
• It has root (Attached margin) & free margin ( intestinal margin) .
• The root in attached to an oblique line across the posterior abdominal
wall extending from duodenojejunal flexure to ileocaeeal junction .
• The root is about 6 inches whiles its free margin in 6 m long .
Small Intestine

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• This accounts for the formation of folds ) pleats in it ( a frill - like
arrangement resembling a full skirt)
Some
differences :
Small Intestine

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Small Intestine

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Applied Anatomy:
Small Intestine

Introductio
n :
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Duodenu
m
• It is first , shortest , widest and most fixed part a small Intestine
• It extends from pylorus to duodenojejunal flexure .
• It is about 25 cm .
• It is C - shaped and is located in the abdominal cavity
above level of umbilicus opposite to L1 , L2, L3.
Parts and Relations :
• 25 cm long duodenum divided into 4
parts :

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(A) Superior = 5cm [ First Part]
(b) Descending = 7.5cm [ second Part]
(c) Horizontal = 10cm [ Third Part]
(d) Ascending = 2.5 cm [ fourth Part]
First
Part
• It develops from foregut .
• It is only partly retroperitoneal .
• It is freely mobile and distensible .
• It has no circular folds in mucous membrane of its initial 2- 5
cm .
• It is site for duodenal ulcer .
• Supplied by branches of coeliac trunk / artery .
Duodenu
m

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Relations
: • ANTERIORLY : Quadrate lobe of liver and gallbladder .
• POSTERIORLY : Portal Vein , gastro duodenal Artery and CBD
• SUPERIORLY : Epilploic foramen being separated from it by portal vein and bile duct .
Duodenu
m

• Its upper half develops from foregut and lower half from midgut.
• It lies behind transverse mesocolon
• It receives bile duct , the chief and accessory pancreatic ducts.
• It is the only part of intestine supplied by double rows vasa recta , arising from anterior and posterior pancreatic o duodenal A.
Relations:
• ANTERIORLY : Gallbladder and right lobe of liver , transverse colon , mesocolon and coils of small intestine .
• POSTERIORLY : Right kidney and right renal vessels , right edge of inferior vena Cava and Right psoas major muscle .
• MEDIALLY : Head of Pancreas .
• LATERALLY : Ascending colon , right colic flexure . and right lobe of liver .
Second Part: Duodenu
m

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Relations:
• ANTERIORLY : Root of mesentery , superior mesenteric vessels , & coils of jejunum .
• POSTERIORLY : Right psoas major , right ureter , IVC , abdominal aorta , and right gonadal
vessels.
• SUPERIORLY : Head of pancreas with its uncinate process .
• INFERIORLY : Coils of jejunum .
Third Part Duodenu
m

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Relations:
• ANTERIORLY : Transverse colon & transverse mesocolon .
• POSTERIORLY : left psoas major muscle , left sympathetic chain , left gonadal
vessels , and inferior mesenteric vein .
• SUPERIORLY : Body of pancreas .
Fourth Part:
• ON TO RIGHT: Upper part of Root of mesentery
Duodenu
m

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Interior of
Duodenum
• The mucous membrane of the duodenum presents circular folds called Valves of KercKring but they
begin in 2nd part .
• Second Part also have
(a) Major duodenal papilla : 8 - 10 cm distal to pylorus • on its summit opens the common hepato
pancreatic duct
(b) Minor duodenal papilla :
• 2cm proximal to major duodenal papilla .
• Accessory pancreatic duct opens on its summit -
(c) Arch of plica semicircularis :
• Forms an arch above the major duodenal papilla
like hood . ( Monk's hood )
Duodenu
m

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Arterial supply
: • Upper half of duodenum develops from foregut and lower half from
midgut .
• The arterial supply of upper half Coeliac Trunk ( A . of foregut ) lower half
= Superior mesenteric Artery (A. of midgut )
Duodenu
m

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Venous Drainage
• Veins correspond to arteries but are superficial to them .
• They drain into splenic , superior mesenteric and portal veins .
Lymphatics
• Drain into Pancreatico duodenal Nodes .
• From here it drains into coeliac & Superior mesenteric lymph nodes and ultimately into
cisterna chyli. via intestinal lymph .
Nerve supply
• Sympathetic nerves to duodenum = T6 - T9 ,
• Parasympathetic nerves = Vagi through coeliac & Superior mesenteric plexus .
Duodenu
m

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Applied Anatomy :
Duodenu
m

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Introduction
• It is the large dilated blind sac at the proximal end of large Intestine.
• situated in the right iliac fossa above the lateral half of inguinal ligament .
• It communicates : (a) Superiorly with ascending colon . (b) Medially at ileocaecal junction with ileum
(c) Posteromedially with appendix .
Shape :
• It is dilated pendulous sac inferior to ileocaecal junction .
• At birth , it is conical in shape , later the canal growth results in formation of two saccules on either
side of anterior teniae coli .
• Growth of Right saccule is greater so the appendix are pushed towards the left .
• As a result , base of appendix is attached at postero medial wall of caecum
• Length : 6cm Types of Caecum : Width : 7.5cm
Caecum

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Shape
:
Types of Caecum
Caecum

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• Conical ( 2%) : caecum is, conical and appendix at its apex
• Infantile (3% ) : The caeaem is quadrate in shape and the appendix in attached at depressed
bottom.
• Normal type ( 80 - 90%. ) : Right saccule is larger and appendix is attached on postero medial
aspect above 2cm of ileocaecal junction .
• Exaggerated (4-5%) : Right saccule is immensely large and left saccule is absent . The appendix
is attached just below the ileocaecal junction .
Visceral Relations -
ANTERIOR
(1) Coils of small intestine
(2) Greater omentum
(3) Anterior abdominal
wall
Caecum

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POSTERIOR
(1) Right psoas major and iliacus muscles .
(2) Femoral Nerve , lateral - cutaneous nerve g thigh & genitofemoral nerve of Right side
(3) Right gonadal vessels .
(4) Right external iliac artery
(5) Retro caecal recess .
Peritoneal Relations
• In 90% individuals , caecum is completely surrounded by peritoneum
• In upto 10 % , the upper part of its posterior surface is non - peritoneal
and lies directly on fascia iliaca .
Caecum

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Interior of Caecum
• The interior of caecum presents two orifices - ileocaecal orifice &
appendicular orifice .
• The ileocaecal orifice is prominent feature of interior of caecm.
ILeocaecal orifice
• About 2.5cm transversely .
• Guarded by Ileocaecal valve . • The valve has two lips : Upper ( smaller ,
longer & horizontal ) and lower concave.
• Two lips join and make Caecal fnenula ( act as coeco colic sphincter)
Caecum

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Appendicular orifice
• It is a small orifice situated 2cm below and behind the ileocaeeal
Orifice .
• Guarded by Value of Gerlach attached to lower margin of opening .
Caecum

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Blood supply & lymphatics
• The caecum is supplied by the anterior and posterior caecal branches of ileo
• - colic artery . a branch of superior mesenteric artery .
• Veins follow arteries & drain into Superior Mesenteric Vein
• Lymph vessels Ileocolic lymph Nodes Portal system Superior Mesenteric Group of Pre -aortic
→
lymph nodes .
Caecum

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Nerve Supply
• Sympathetic = and Lt [ Superior Mesenteric Plexus]
• Parasympathetic = Vagus Nerves .
Applied
Caecum

Introductio
n
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Vermiform
Appendix
• It is a narrow worm like diverticulum which arises from the posteromedial wall of caecum
about 2cm below ileocaecal junction .
• It can be 2 to 20cm long.
• Width is about 5mm , diameter of lumen varies with age .
(a) base
(b) body
(c) tip
• Three parts

Surface
Anatomy
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• The base of appendix is marked on surface by a point 2cm
below the intersection between the trans tubercular plane and
right midclavicular line (right lateral plane )
Positio
n
• The appendix usually lies in right iliac fossa -
• Base is fixed but the remaining part may occupy any of the following
positions , which are often indicated with hour hand commonest, 12 o
clock .
Vermiform
Appendix

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• The vermiform appendix is an intra peritoneal structure .
• The appendix is suspended by a small triangular fold of the peritoneum derived from the
posterior / left layer of mesentery of ileum.
• It is called the mesentery of appendix or meso appendix .
Arterial - supply
• Supplied by a single appendicular artery . a branch of inferior division
of ileo colic artery .
Venous Drainage
• The vein corresponds to artery and drains into the superior
mesenteric Vein Portal Vein .
→
Vermiform
Appendix

Lymphatic Drainage
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• The lymph vessels of appendix drain into ileocolic lymph nodes directly or through
appendicular nodes in meso appendix .
Nerve Supply
• Sympathetic : Pain sensation (T 10) via lesser splanchnic nerve
& superior mesenteric plexus . - Pain is referred to umbilical
region .
• Parasympathetic : Vagus Nerves .
Vermiform
Appendix

Microscopic structure
:
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Vermiform
Appendix

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Applied Anatomy Vermiform
Appendix

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Colon
• Four parts :
Introduction
• Upward continuation of caecum .
• About 5 inch ( 12.5cm )
• Extends from Caecum at ileocaecal orifice to inferior surface of right lobe of liver when it
forms hepatic flexure ( right colic) .
(a) Ascending colon
(b)Transverse colon
(c) Descending colon
(d) Sigmoid colon .
Ascending Colon

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• Front and sides are covered by Peritoneum , which binds it to
posterior abdominal wall .
• Its posterior surface lies on three muscle : Iliacus , quadratus
( lamborum and transversus abdominis .
• It is longest ( 20 inch 150cm ) and most mobile part of large
Intestine
• Extends from right colic to left colic flexure .
• The lowest point usually extends up to level of umbilicus but may
sometimes into pelvis .
• Not actually transverse but usually U-Shaped
Transverse colon
Relation
• ANTERIOR-Greater omentum & Abd . wall
• POSTERIOR - second part of duodenum , head of pancreas and coils of small Intestine .
Colon

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• It is longer ( 25cm) , narrower and more deeply located than
ascending colon .
• Extends from left colic flexure to the front of left external iliac
artery at level of pelvic brim .
• Covered by peritoneum on the front and sides which fixes it in left
paracolic gutter and iliac fossa .
Descending Colon
Relations
• When descending , it passes in front of three muscles and three nerves
• Muscles are quadratus lamborum . transversus abdominis and iliacus .
• The nerves are iliohypo gastric , ilioinguinal and lateral cutaneous nerves of thigh .
• Distal part turns medially from the left iliac fossa to the the front of left external iliac Vessels . During this it
passes in front of femoral N . psoas as major muscle , testicular vessels , genitofemoral N . and left external
iliac Vein.
Colon

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• Also called Pelvic Colon .
• It is about ( 37.5 cm ) and connect descending colon with Rectum.
• S-shaped
• Extends from lower end of descending colon at left pelvic inlet to the pelvic surface of
third sacrum , where it continues with Rectum
• Consists of Three parts :
• (a) first part runs downward
• (b) second part transverses horizontally
• (c) third part runs backward .
Sigmoid Colon:
Colon

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Differences
Colon

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Arterial supply :
Colon is supplied by following
arteries :
(a) Ileocolic artery - smaller part of Ascending colon .
(b) Right colic artery - larger upper part of Ascending
colon (c) Middle colic artery - Right 2/3rd of Transverse
colon
(d) Left colic artery . - left 1/3rd of Transverse colon &
Descending colon .
(e) Sigmoid Arteries -
(f) superior rectal Arteries
sigmoid colon
Colon

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Venous Drainage
(1) The veins draining the colon accompany the
arteries .
(2) The veins accompanying
ileocolic
Right colic } Join the Superior Mesenteric
Vein .
Middle colic
• Veins accompanying branches of Inferior mesenteric artery join the inferior
mesenteric vein.
• Superior and inferior mesenteric Veins finally drain into Portal Vein
Colon

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Lymphatics:
(1) Epiploic nodes
(2) Para colic nodes
(3) Intermediate colic
nodes
(4) the terminal nodes .
Colon

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Applied Anatomy:
Colon

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Sites of Carcinoma in Colon :
Colon

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RECTUM
The rectum is the most distal segment of the large intestine, and has an important role as a
temporary store of faeces.
It is continuous proximally with the sigmoid colon, and terminates into the anal canal.
Anatomical Structure
The rectum begins at the level of the S3 (as a continuation of the sigmoid colon). It is macroscopically distinct from
the colon, with an absence of taenia coli, haustra, and omental appendices.
The course of the rectum is marked by two major flexures:
Sacral flexure – anteroposterior curve with concavity anteriorly (follows the curve of the sacrum and coccyx).
Anorectal flexure – anteroposterior curve with convexity anteriorly. This flexure is formed by the tone of the
puborectalis muscle, and contributes significantly to faecal continence.
There are additionally three lateral flexures (superior, intermediate and inferior), which are formed by transverse
folds of the internal rectum wall.
The final segment of the rectum, the ampulla, relaxes to accumulate and temporarily store faeces until defecation
occurs. It is continuous with the anal canal; which passes through the pelvic floor to end as the anus.
Peritoneal coverings

RECTUM
The rectum is located within the pelvic cavity, and is the most posterior of the pelvic viscera. Its
anatomical relations are different in men and women
Neurovascular Supply
The rectum receives arterial supply through three main arteries:
•Superior rectal artery – terminal continuation of the inferior mesenteric artery.
•Middle rectal artery – branch of the internal iliac artery.
•Inferior rectal artery – branch of the internal pudendal artery.
Venous drainage is via the corresponding superior, middle and inferior rectal veins. The superior rectal vein empties into the portal venous system,
whilst the middle and inferior rectal veins empty into the systemic venous system. Anastomoses between the portal and systemic veins are located in the
wall of anal canal, making this a site of portocaval anastomosis.
Note: the rectum is also closely anatomically associated with the rectal venous plexus; however this structure is more functionally related to the anal canal.
Innervation
The rectum receives sensory and autonomic innervation.
Sympathetic nervous supply to the rectum is from the lumbar splanchnic nerves and superior and inferior hypogastric plexuses. Parasympathetic supply
is from S2-4 via the pelvic splanchnic nerves and inferior hypogastric plexuses. Visceral afferent (sensory) fibres follow the parasympathetic supply.

Lymphatic Drainage
Lymphatic drainage of the rectum is via the pararectal lymph nodes, which drain into the inferior
mesenteric nodes.
Additionally, the lymph from the lower aspect of the rectum drains directly into the internal iliac lymph
nodes.
RECTUM
Clinical Relevance - Digital Rectal Examination
The anterior wall of the rectum has a number of close anatomical structures. These can therefore be
palpated digitally via the rectum. Most significant are the prostate and seminal vesicles in males, and
cervix in females. Bony structures, such as the sacrum and coccyx, may also be palpated in both sexes.

The Anal Canal
The anal canal is the final segment of the gastrointestinal tract.
It has an important role in defecation and maintaining faecal continence.
Anatomical Position
The anal canal is located within the anal triangle of the perineum between the right and left ischioanal fossae. It is the final segment
of the gastrointestinal tract, around 4cm in length.
The canal begins as a continuation of the rectum and passes inferoposteriorly to terminate at the anus.
Except during defecation, the anal canal is collapsed by the internal and external anal sphincters to prevent the passage of faecal material.
Anal Sphincters
The anal canal is surrounded by internal and external anal sphincters, which play a crucial role in the maintenance of faecal continence:
•Internal anal sphincter – surrounds the upper 2/3 of the anal canal. It is formed from a thickening of the involuntary circular smooth
muscle in the bowel wall.
•External anal sphincter – voluntary muscle that surrounds the lower 2/3 of the anal canal (and so overlaps with the internal sphincter). It
blends superiorly with the puborectalis muscle of the pelvic floor.
At the junction of the rectum and the anal canal, there is a muscular ring – known as the anorectal ring. It is formed by the fusion of the
internal anal sphincter, external anal sphincter and puborectalis muscle, and is palpable on digital rectal examination.
rnal Structure
superior aspect of the anal canal has the same epithelial lining as the rectum (columnar epithelium). However, in the anal
l, the mucosa is organised into longitudinal folds, known as anal columns. These are joined at their inferior ends by anal
es. Above the anal valves are small pouches which are referred to as anal sinuses – these contain glands that secrete mucus.
anal valves collectively form an irregular circle – known as the pectinate line (or dentate line). This line divides the anal canal
upper and lower parts, which differ in both structure and neurovascular supply. This is a result of their different embryological
ns:
ove the pectinate line – derived from the embryonic hindgut.
ow the pectinate line – derived from the ectoderm of the proctodeum.
rior to the pectinate line, the anal canal is lined by non-keratinised stratified squamous epithelium (known as the anal
en). It is a pale and smooth surface, which transitions at the level of the intersphincteric groove to true skin (keratinised
ified squamous).
ternal Structure
he superior aspect of the anal canal has the same epithelial lining as the rectum (columnar epithelium). However, in the anal
nal, the mucosa is organised into longitudinal folds, known as anal columns. These are joined at their inferior ends by anal
alves. Above the anal valves are small pouches which are referred to as anal sinuses – these contain glands that secrete mucus.
he anal valves collectively form an irregular circle – known as the pectinate line (or dentate line). This line divides the anal canal
to upper and lower parts, which differ in both structure and neurovascular supply. This is a result of their different embryological
igins:
bove the pectinate line – derived from the embryonic hindgut.
elow the pectinate line – derived from the ectoderm of the proctodeum.
ferior to the pectinate line, the anal canal is lined by non-keratinised stratified squamous epithelium (known as the anal
ecten). It is a pale and smooth surface, which transitions at the level of the intersphincteric groove to true skin (keratinised
ratified squamous).

The Anal Canal
The anal canal lies in close proximity to several other important structures in the pelvis and
perineum:
Neurovascular Supply and Lymphatics
As discussed above, the pectinate line divides the anal canal into two parts – which have a different arterial supply, venous drainage,
innervation and lymphatic drainage.
Modality Above Pectinate line Below Pectinate line
Arterial Supply
Superior rectal artery (branch of inferior mesenteric artery)Anastomosing
branches from the middle rectal artery.
Inferior rectal artery (branch of the
internal pudendal artery)Anastomosing branches from the
middle rectal artery.
Venous Drainage Superior rectal vein, which empties into the inferior mesenteric vein (portal
venous system).
Inferior rectal vein, which empties into the
internal pudendal vein (systemic venous system).
Nerve Supply
Visceral innervation via the inferior hypogastric plexus.Sensitive to stretch.
Somatic innervation via the inferior rectal nerves
(branches of the pudendal nerve)Sensitive to pain,
temperature, touch and pressure.
Lymphatics Internal iliac lymph nodes Superficial inguinal lymph nodes

The Anal Canal
Clinical Relevance - Haemorrhoids
Haemorrhoids are vascular cushions found within the anal canal of healthy
individuals, which help with the maintenance faecal continence. If they
become swollen and distended, they are referred to as pathological
haemorrhoids.
Pathological haemorrhoids are observed in people who suffer
from constipation, prolonged straining when defecating, or raised intra-
abdominal pressure (e.g pregnancy, ascites). Upon examination of the anal
canal (with the patient in the lithotomy position), the haemorrhoids are
typically located at the 3, 7 and 11 o’clock positions.
They can cause bleeding and itchiness, and depending on the severity, can
be managed conservatively or surgically.

Introductio
n
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Abdominal Organ - liver
• The liver in the largest gland of the body occupying much of the right upper part of
abdominal cavity .
(1) It secretes bile and stones glycogen (2) It synthesizes the serum proteins & lipids .
(3) ) It detoxifies blood from foreign substances . (4) gt produces hemopoielic cells of all types
during fetal life .
• It in present in right hypochondrium , upper part of epigastrium , and part is left
hypochondrium upto middauicnlar line.
• It lies mostly under cover g ribs & costal cartilages immediately below diaphragm .
• It extends upward as far as 5th Rib [Right, and left 5th Intercostal space [left side ] .

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• shape = It in a wedge shaped and resembles a four -
sided pyramid laid on one side with its base directed
towards the right and opex towards left .
• Weight : Male - - 1.4 to 1.8kg
• Females = 1.2 to 1.4kg
• Newborn - - 1/18 th of body wt .
• Birth - 150g .

External features
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• Two surfaces :
(1) Diaphragmatic (2) Visceral
• One border : Inferior

Inferior Border
features
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• (a) It separates the diaphragmatic surface from the visceral surface
• (b) It in rounded laterally when it separates the right lateral surface from inferior surface .
(C)Two Notches: (1) Notch for big ligamentum teres (2) cystic Notch .
(d) In epigastrium it extends from the night 9th costal cartilage to 8th left costal cartilage ,
thus ascends sharply to left .
(e) In median plane , it lies in trans pyloric plane .
Lobes of
liver
Two types : (a) Anatomical lobes (b) physiological lobes .
Anatomical lobe
On the Diaphragmatic surface Two lobes right & left:
Right: (Greater than left)

On Visceral surface , it has 4
lobes :
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(a) Right (b) Left (c) Quadrate (d) Caudate
Size of both lobes are equal .
Physiological lobes
• liver in divided into Right & left physiological lobes by
imaginary sagittal plane / line (cantlie's plane / line) .

Hepatic segments
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These are structural units of liver , there are Eight hepatic segments .
• Right physiological lobe =
Upper & lower Parts .
• Left physiological lobe = Medial
& lateral Parts .
• Each Parts are then divided into
upper & lower .
• These 8 segments .

Couinaud 's Nomenclature :
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• Segments are numbered I to VIII
• I to IV = left hemi liver
• V to VIII = Right hemi liver -
• Segment I corresponds to
Caudate lobe and quadrate lobe

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Blood Supply
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• Highly vascular organ -
• It receives blood from two sources
• Nearly 1/3rd of Cardiac Output
passes through liver.
Hepatic Artery (oxygenated )
portal Vein ( Deoxy. )
80%. by Portal Vein
20% by Hepatic Artery .
Venons Drainage
(a) left hepatic Vein [b/w medial &lateral segments of left lobe)
(b) Middle hepatic Vein [ b/w Right & left lobes ]
(c) Right hepatic Vein [ b/w Ant . Post segment , Right lobe]

Lymphatic
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• Superficial lymphatics
• Portal lymphatics [80%]
• Sublobular lymphatics
(3 Categoria )
Nerve
supply
• Sympathetic [from coeliac plexus]
• Parasympathetic [ from hepatic branch Ant - Vagal Nerve]
Development
• liver develops from a diverticulum [hepatic bud )
from distal end g foregut .
• Hepatic bud → Pars cystica ( Accessory, bud ) cystic
duct & Gallbladder .
• Main bud ( Pars hepatica) liver .
→

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ExtrahepaticBiliary Apparatus
The extra hepatic biliary apparatus receives the bile from liver , stores and concentrates it in
gallbladder and then transmits to duodenum when required .
Hepatic Ducts:
• Right & left hepatic ducts from Right and left lobes of liver
emerges through porta hepatis , and unite to form
Common hepatic duct .
Five components :
(a) Right & left hepatic ducts
(b) Common hepatic duct (c) Gallbladder (d) Cystic
duct (e) Bile duct

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• It passes downward for 2. 5 cm and then joined by cystic
duct to form Common Bile Duct .
• Angle between cystic duct & common hepatic duct is
acute and called Cystohepatic Angle .
Gallbladder
• gallbladder is a pear - shaped sac.
• Store bile
• Fatty food induces Cck from duodenal cells which in turn causes muscles of gall bladder to
contract and thus the release of bile occurs.
• Location : It lies in the fossa for gallbladder on inferior surface of right lobe of liver along right
edge of quadrate lobe .
• Dimensions : length - - 10cm - width = 3cm ( at its widest part)

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• Divided into 3 parts :
• (a) Fundus (b) Body (c) Neck
Fundus
• Expanded ( blind end )
• Completely surrounded by, peritoneum
.
• It is related anteriorly to ant .
abdominal wall & post . to transverse
colon .

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Body
• It is directed upward , backward , and to left to join the neck at right end of porta
hepatis .
• Its upper surface is related directly to the liver and in devoid of peritoneum .
• Undersurface covered by peritoneum .
Neck
• It is narrow upper end of gallbladder .
• Joins cystic duct
• Attached to liver by loose areolar tissue in. which cystic artery is embedded .
• Its postenmedial wall shows a pouch - called Hartmann's Pouch directed downward and
backward .

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Wall of gallbladder has 4 layers
• Serous layer (peritoneum )
• Subserous layer (loose areolar tissue )
• Fibromuscular layer - (smooth muscle)
• Mucous memberane fibrous tissue ( flat columnar )
Arterial supply
• Supplied by cystic artery [ a branch right hepatic
artery ] .
• It may arise from the main trunk a hepatic Artery ,
from left hepatic Artey or from Gastroduodenal A.
Venous Drainage
• By cystic vein Portal Vein
→
• By small no of veins Hepatic Vein .
→

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Lymphatic Drainaye
• Majority drain into (a) , cystic lymph nodes of Lund (In Calot's triangle)
• (b) Nodes at upperside of bile duct . ( Drains into) coeliac group Lymph nodes
• Some lymph vessels directly communicate with subscapular lymph vessels of
liver .
Nerve Supply
• Via cystic plexus by sympathetic fibers ( T5 - T9)
• Parasympathetic fibres
• Fibers of Right Phrenic

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Cystic Duct
• About 3 -5 cm
• Faction with common hepatic duct below porta hepatic .
• The mucous membrane lining the interior of cystic duct in
thrown into a series g cresenteric folds 5- 10 in number .
• They project into the lumen in a spiral fashion forming a spiral
fold called
• spiral valve ( of Heister )
Bile duct common Bile duct :
• It in formed near the porta hepatic by union of cystic and
common hepatic ducts .

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• It is formed near the porta hepatis by union of cystic and common
hepatic ducts .
• It is usually 15cm long and 6mm in diameter.
• Divided in four parts :
• (1) Supraduodenal
• (2) Retro duodenal
• (3) Infra duodenal
• (4) Infraduodenal .
Arterial supply
• Upper part :
• By a small branch from the descending branch of cystic Artery
• Lower Part :
• By Ascending branch 7 Superior pancreaticoduodenal Artery .

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Cystohepatic Triangle of Calot
• It is bounded on right side by cystic duct , Left side by Common hepatic duct Above by Inf. surface
liver
• The identification of cystohepatic triangle and its contents helps the surgeon to locate the pedicle of
gallbladder in cholecystectomy .

Introductio
n
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Pancreas
• The pancreas is a soft ,finely lobulated ,elongated exocrine gland .
• The pancreatic juice helps in digestion of lipids , carbohydrates . and proteins whereas
pancreatic hormones maintain glucose homeostasis .
(a) base
(b) body
(c) tip
• J-shaped , with
Locatio
n• The pancreas lies on posterior wall in Epigastric & left hypochondriac regions & between T12 -
L3 vertebrae -

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• The greater part of gland is retro peritoneal behind the serous floor
of lesser sac .
• Its left extremity - the tail . lies in the lienorenal ligament .
4
Part
s
• It is the enlarged . disc - shaped right end of pancreas ,
which lies in concavity of C - shaped duodenal loop in front
of L2 .
(1) Head
(2) Neck
(3) Body
(4) Tail
Head of Pancreas

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External Features
• superior border
Relations
superior
Inferior
Right lateral
(1) Three borders
(2) Two surfaces - Anterior & Posterior
(3) One process - Uncinate Process .
(a) First part of duodenum
(b) Superior pancreatic o duodenal
Artery .
• Inferior border
(a) third part of duodenum
(b) inferior pancreatic duodenal A. .
• Right lateral
border
(a) Second part of duodenum
(b) ant . 2 post. pancreatic duodenal
Arterial arcades .

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• Anterior surface
(a) gastro duodenal A .
(b) transverse colon
(c) root of transverse mesocolon
(d) Jejunum
• Posterior Surface
(a) IVC
(b) left Renal Vein
(c) Bile duct
(d) Right crus of diaphragm
• Uncinate process
(a) Anteriorly to superior mesenteric vessels
(b) posteriorly to abdominal aorta .

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Neck of Pancreas
• It is a slightly constricted part of gland which connects the head with body . It is about 2.5 cm long and is
directed forward,upward and to the left
External features
• It presents the following external features : Two surfaces : Anterior and posterior ,Two borders : upper &
lower .
Relations
• Anterior surface is related to pylorus
• Posterior surface = Commencement of Postal
vein
• Upper border = first part of duodenum .
• lower border = Root of transverse meso colon .

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Body of Pancreas
• It is elongated part of gland extending from its neck to tail .
• It passes towards the left of midline with a slight upward and backward inclination.
• It lies in front of Vertebral Column .
External features
• It is somewhat triangular in cross section and
presents :
(1) Three
borders
Anterior
Superior
Inferior
(2) Three
surfaces
Anterior
posterior
Inferior
(3) One process
Tuber
omentale

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Relations
• Anterior border = Provides attachment to root of transverse mesocolon
• Superior border = Related to coeliac artery .
• Inferior border : superior mesenteric vessels
• Anterior surface : (a) lesser sac (b) stomach .
• Posterior surface : (a) Aorta (b) left kidney (c) Splenic vein usually lies
• Inferior surface : (a) duodenojejunal flexure . (b) Coils of jejunum (c) left colic flexure

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Tail of Pancreas
• It is narrow left extremity of Pancreas
• Lies in linorenal ligament
• It is mobile
• It contains the largest number of islets of Langerhans per unit .
Relations
• These are related to visceral surface of
spleen between gastric impression and
colic impression .

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Ducts of Pancreas
• Usually there are two ducts (a) Main Pancreatic duct [ of Wirsung)
(b) Accessory Pancreatic duct [ of Santorini]
Main Pancreatic
duet
(a) It begins in tail and traverse the whole length of gland near its posterior surface .
(b) At the neck , it turns downward and then to the right to enter into second part of
duodenum .
(c) It joins bile duct from hepato pancreatic ampulla of Vater
(d) It is the only duct in 90% cases .

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Accessory Pancreatic duct
• It begins in lower part of head .
• Opens into second part of duodenum ( about 2--3 cm above main pancreatic
duct )
• In 40% cases , it communicates with main duct while crossing it .
Arterial-supply
(a) Splenic Artery ( coeliac trunk)
(b) Superior pancreatic o duodenal Artery branch of (Gastro duodenal
A.)
(c) Inferior pancreaticoduodenal Artery ( superior mesentery A.)

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Venous Drainage
(a) Portal Vein
(b) Superior mesenteric Vein
(c) Splenic Vein.
Arterial-supply
(a) splenic Artery ( coeliac trunk)
(b) superior pancreatic o duodenal Artery branch of( Gastro duodenal
A )
(c) Inferior pancreatic duodenal Artery ( superior mesentery A.)

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Lymphatic
drainage
The lymphatics from the pancreas follow the arteries and drain mainly into the following
groups :
Nerve Supply
(a) Pancreaticosplenic Nodes (main)
(b) Coeliac nodes
(c) Superior mesenteric nodes .
(d) Pyloric nodes .
• The sympathetic and parasympathetic Nerve
fibers reach gland along its arteries from
coeliac and superior mesenteric plexus.
• Sympathetic = Vasomotor ( on blood vessels )
• Parasympathetic = Pancreatic secretion.

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Development
Pancreas develops from two separate buds :
(a) Ventral Pancreatic bud
(b) Dorsal Pancreatic bud .
• The smaller Arises in common with
hepatic bud
• The larger More proximally directly
from duodenum
• later both buds join together.

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Stages

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Applied
:

Introductio
n
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Spleen
• The spleen is the largest lymphoid organ in body .
(a) To filter blood by removing worn-out RBCs and microbial agents
from the circulation.
(b) To manufacture RBCs in fetal life and lymphocytes after birth .
(c) To provide immunity to the body by producing IgM by plasma cells .
(d) To store RBCs and release them in circulation when required
Location
• Functions
include :
• The spleen is located in the left hypochondrium between the fundus of stomach and the
diaphragm behind the mid axillary line opposite the 9th , 10th and 11th ribs .

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• Its long axis lies parallel to the long axis of the 1oth rib and moves a bit in living during
respiration.
Size , shape and colour
• The spleen is a wedge - shaped soft organ with purple colour . The size of
spleen roughly corresponds to the fist of the subject .
Classification
Spleen

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Measureme
nt
Thickness = 1 inch Breadth = 3 inch length = 5 inch
Weight = 200gm .
External Features
• The spleen presents the following external
features :
(1) Two ends [ Anterior & Posterior ]
(2) Three borders [superior , inferior & intermediate ]
(3) Two surfaces [ diaphragmatic & Visceral ]

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Relations
• Spleen is completely enclosed in the peritoneum except at its hilum from when two
peritoneal folds extend - one to stomach = Gastrosplenic ligaments . One to left kidney =
binominal ligaments .
• Gastrosplenic ligament extends from the hilum of the spleen to upper one - third of the
greater curvature of stomach . It contains short gastric vessels .
• Linorenal ligament : extends from the hilum of spleen to the ant . surface of kidney . It
contains (a) tail of pancreas (b) splenic vessels (c) Pancreaticosplenic lymph Nodes

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Visceral Relations
• Related to -
• Fundus of stomach
• Ant. surface of left
kidney
• left colic flexure
• Tail of pancreas .
Arterial Supply
• The spleen is supplied by splenic Artery , largest branch of
Coeliac trunk
• It traverses through the linorenal ligament to reach near the
hilum of spleen , and divided into 5 branches or more .

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Visceral Relations
• Diffuse type of spleen - If terminal branches are long
• Compact if terminal branches are small .
Venous Drainage
• The venous blood is drained by splenic vein .
• Joins the superior mesenteric vein to form portal
vein .
• Its tributaries are
(1) Short Gastric vein
(2) Left gastroepiploic .
(3) Pancreatic veins
(4) Inferior mesenteric veins

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Lymphatic Drainage
• No lymphatics
• The splenic lymphatics are confined to its trabeculae, capsule , and visceral peritoneum .
• They drain along splenic vessels into the pancreaticolienal lymph nodes .
• Spleen is supplied by sympathetic fibres
derived from the coeliac plexus.
Nerve Supply

The Kidneys
The kidneys are bilateral bean-shaped organs, reddish-brown in colour and located in the posterior
abdomen. Their main function is to filter and excrete waste products from the blood. They are also
responsible for water and electrolyte balance in the body.
Metabolic waste and excess electrolytes are excreted by the kidneys to form urine. Urine is
transported from the kidneys to the bladder by the ureters. It leaves the body via the urethra, which
opens out into the perineum in the female and passes through the penis in the male.
Anatomical Position
The kidneys lie retroperitoneally (behind the peritoneum) in the abdomen, either side of the vertebral
column.
They typically extend from T12 to L3, although the right kidney is often situated slightly lower due to the
presence of the liver. Each kidney is approximately three vertebrae in length.
The adrenal glands sit immediately superior to the kidneys within a separate envelope of the renal fascia.
Kidney Structure
The kidneys are encased in complex layers of fascia and fat. They are arranged as follows (deep to superficial):
•Renal capsule – tough fibrous capsule.
•Perirenal fat – collection of extraperitoneal fat.
•Renal fascia (also known as Gerota’s fascia or perirenal fascia) – encloses the kidneys and the suprarena
glands.
•Pararenal fat – mainly located on the posterolateral aspect of the kidney.

Kidney Structure
The kidneys are encased in complex layers of fascia and fat. They are arranged as follows (deep to superficial):
•Renal capsule – tough fibrous capsule.
•Perirenal fat – collection of extraperitoneal fat.
•Renal fascia (also known as Gerota’s fascia or perirenal fascia) – encloses the kidneys and the suprarenal gland
•Pararenal fat – mainly located on the posterolateral aspect of the kidney
Internally, the kidneys have an intricate and unique structure. The renal parenchyma can be divided
into two main areas – the outer cortex and inner medulla. The cortex extends into the medulla,
dividing it into triangular shapes – these are known as renal pyramids.
The apex of a renal pyramid is called a renal papilla. Each renal papilla is associated with a structure
known as the minor calyx, which collects urine from the pyramids. Several minor calices merge to form
a major calyx. Urine passes through the major calices into the renal pelvis, a flattened and funnel-
shaped structure. From the renal pelvis, urine drains into the ureter, which transports it to the bladder
for storage.
The medial margin of each kidney is marked by a deep fissure, known as the renal hilum. This acts as a

The kidneys are supplied with blood via the renal arteries, which arise directly from the abdominal aorta,
immediately distal to the origin of the superior mesenteric artery. Due to the anatomical position of the
abdominal aorta (slightly to the left of the midline), the right renal artery is longer, and crosses the vena cava
posteriorly.
The renal artery enters the kidney via the renal hilum. At the hilum level, the renal artery forms an anterior and
a posterior division, which carry 75% and 25% of the blood supply to the kidney, respectively. Five segmental
arteries originate from these two divisions.
The avascular plane of the kidney (line of Brodel) is an imaginary line along the lateral and slightly posterior
border of the kidney, which delineates the segments of the kidney supplied by the anterior and posterior
divisions. It is an important access route for both open and endoscopic surgical access of the kidney, as it
minimises the risk of damage to major arterial branches.
Note: The renal artery branches are anatomical end arteries – there is no communication between vessels. This is of
crucial importance; as trauma or obstruction in one arterial branch will eventually lead to ischaemia and necrosis of
the renal parenchyma supplied by this vessel.
The segmental branches of the renal undergo further divisions to supply the renal parenchyma:
•Each segmental artery divides to form interlobar arteries. They are situated either side every renal pyramid.
•These interlobar arteries undergo further division to form the arcuate arteries.
•At 90 degrees to the arcuate arteries, the interlobular arteries arise.
•The interlobular arteries pass through the cortex, dividing one last time to form afferent arterioles.
•The afferent arterioles form a capillary network, the glomerulus, where filtration takes place. The capillaries
come together to form the efferent arterioles.
In the outer two-thirds of the renal cortex, the efferent arterioles form what is a known as a peritubular
network, supplying the nephron tubules with oxygen and nutrients. The inner third of the cortex and the
medulla are supplied by long, straight arteries called vasa recta.

Clinical Relevance: Variation in Arterial Supply to the Kidney
The kidneys present a great variety in arterial supply; these variations may be explained by the ascending
course of the kidney in the retroperitoneal space, from the original embryological site of formation (pelvis)
to the final destination (lumbar area). During this course, the kidneys are supplied by consecutive branches of
the iliac vessels and the aorta.
Usually the lower branches become atrophic and vanish while new, higher ones supply the kidney during its
ascent. Accessory arteries are common (in about 25% of patients). An accessory artery is any supernumerary
artery that reaches the kidney. If a supernumerary artery does not enter the kidney through the hilum, it is
called aberrant.

Venous Drainage
The kidneys are drained of venous blood by the left and right renal veins. They leave the renal hilum
anteriorly to the renal arteries, and empty directly into the inferior vena cava.
As the vena cava lies slightly to the right, the left renal vein is longer, and travels anteriorly to the abdominal
aorta below the origin of the superior mesenteric artery. The right renal artery lies posterior to the inferior
vena cava.
Lymphatics
Lymph from the kidney drains into the lateral aortic (or para-aortic) lymph nodes, which are located at the
origin
of the renal arteries.
Clinical Relevance: Congenital Abnormalities of the Kidneys
Pelvic Kidney
In utero, the kidneys develop in the pelvic region and ascend to the lumbar retroperitoneal area.
Occasionally, one of the kidneys can fail to ascend and remains in the pelvis – usually at the level of
the common iliac artery.
Horseshoe Kidney
A horseshoe kidney (also known as a cake kidney or fused kidney) is where the two developing
kidneys fuse into a single horseshoe-shaped structure.
This occurs if the kidneys become too close together during their ascent and rotation from the
pelvis to the abdomen – they become fused at their lower poles (the isthmus) and consequently
become ‘stuck’ underneath the inferior mesenteric artery.
This type of kidney is still drained by two ureters (although the pelvices and ureters remain
anteriorly due to incomplete rotation) and is usually asymptomatic, although it can be prone

The Adrenal Glands
The adrenal (or suprarenal) glands are paired endocrine glands situated over the medial aspect of the upper
poles of each kidney.
They secrete steroid and catecholamine hormones directly into the blood.
Anatomical Location and Relations
The adrenal glands are located in the posterior abdomen,
between the superomedial kidney and the diaphragm. They
are retroperitoneal, with parietal peritoneum covering
their anterior surface only.
The right gland is pyramidal in shape, contrasting with the
semi-lunar shape of the left gland.
Perinephric (or renal) fascia encloses the adrenal glands and
the kidneys. This fascia attaches the glands to the crura of
the diaphragm. They are separated from the kidneys by
the perirenal fat.
The adrenal glands sit in close proximity to many other
structures in the abdomen:

The adrenal glands consist of an outer connective tissue capsule, a cortex and a medulla. Veins and
lymphatics leave each gland via the hilum, but arteries and nerves enter the glands at numerous sites.
The outer cortex and inner medulla are the functional portions of the gland. They are two separate endocrine
glands, with different embryological origins:
•Cortex – derived from the embryonic mesoderm.
•Medulla – derived from the ectodermal neural crest cells.
The cortex and medulla synthesise different hormones.
Cortex
The cortex is yellowish in colour. It secretes two cholesterol derived hormones – corticosteroids and
androgens. Functionally, the cortex can be divided into three regions (superficial to deep):
•Zona glomerulosa – produces and secretes mineralocorticoids such as aldosterone.
•Zona fasciculata – produces and secretes corticosteroids such as cortisol. It also secretes a small amount of
androgens.
•Zona reticularis – produces and secretes androgens such as dehydroepiandrosterone (DHES). It also
secretes a small amount of corticosteroids
Medulla
The medulla lies in the centre of the gland, and is dark brown in
colour. It contains chromaffin cells, which secrete catecholamines
(such as adrenaline) into the bloodstream in response to stress.
These hormones produce a ‘flight-or-fight‘ response. Chromaffin
cells also secrete enkephalins which function in pain control

Vasculature
The adrenal glands have a rich blood supply via three main arteries:
•Superior adrenal artery – arises from the inferior phrenic artery
•Middle adrenal artery – arises from the abdominal aorta.
•Inferior adrenal artery – arises from the renal arteries.
Right and left adrenal veins drain the glands. The right adrenal vein drains into the inferior vena cava, whereas
the left adrenal vein drains into the left renal vein.
Innervation
The adrenal glands are innervated by the coeliac plexus and greater splanchnic nerves.
Sympathetic innervation to the adrenal medulla is via myelinated pre-synaptic fibres, mainly from the T10 to L1
spinal cord segments.
Lymphatics
Lymph drainage is to the lumbar lymph nodes by adrenal lymphatic vessels. These vessels originate from two
lymphatic plexuses – one deep to the capsule, and the other in the medulla.
Clinical Relevance: Pheochromocytoma
A pheochromocytoma is a tumour of the adrenal medulla or preganglionic sympathetic neurones. It secretes
adrenaline and noradrenaline uncontrollably, causing blood pressure to greatly increase. Patients may present
with palpitations, headaches and diaphoresis (profuse sweating).
Phenoxybenzamine, a competitive, irreversible antagonist of adrenaline, can be used in treatment to reduce
blood pressure by binding to adrenaline receptors, making less available for adrenaline to act upon.
By TeachMeSeries Ltd (2023)

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The Aorta
The aorta is the largest artery in the body, initially being an inch wide in diameter. It
receives the cardiac output from the left ventricle and supplies the body with oxygenated
blood via the systemic circulation.
The aorta can be divided into four sections: the ascending aorta, the aortic arch, the
thoracic (descending) aorta and the abdominal aorta. It terminates at the level of L4 by
bifurcating into the left and right common iliac arteries. The aorta classified as a large
elastic artery, and more information on its internal structure can be found here.
In this article we will look at the anatomy of the aorta – its anatomical course, branches
and clinical correlations.

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Fig 1 – Overview of the anatomical course of the aorta. By Edoarado
[CC BY-SA 3.0], via Wikimedia Commons

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Ascending Aorta
The ascending aorta arises from the aortic orifice from the left ventricle and ascends to
become the aortic arch. It is 2 inches long in length and travels with the pulmonary trunk
in the pericardial sheath.
Branches
The left and right aortic sinuses are dilations in the ascending aorta, located at the level of
the aortic valve. They give rise to the left and right coronary arteries that supply the
myocardium.
Aortic Arch
The aortic arch is a continuation of the ascending aorta and begins at the level of the
second sternocostal joint. It arches superiorly, posteriorly and to the left before moving
inferiorly.

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The aortic arch ends at the level of the T4 vertebra. The arch is still connected to the
pulmonary trunk by the ligamentum arteriosum (remnant of the foetal ductus arteriosus).
Branches
There are three major branches arising from the aortic arch. Proximal to distal:
Brachiocephalic trunk: The first and largest branch that ascends laterally to split into the right
common carotid and right subclavian arteries. These arteries supply the right side of the head
and neck, and the right upper limb.
Left common carotid artery: Supplies the left side of the head and neck.
Left subclavian artery: Supplies the left upper limb.

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Fig 2 – Schematic of the aortic arch and major branches.

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Clinical Relevance: Coarctation of the Aorta
Coarctation of the aorta refers to narrowing of the vessel, usually at the insertion of the
ligamentum arteriosum (former ductus arteriosus). It is a congenital condition. The
narrow vessel has an increased resistance to blood flow, which increases the after-load
for the left ventricle – leading to left ventricular hypertrophy.
Blood supply to the head, neck and upper limbs is not compromised as the vessels that
supply them emerge proximal to the coarctation. However, blood supply to the rest of the
body is reduced. This results in a weak, delayed femoral pulse which presents clinically as
radio-femoral delay.

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Branches
In descending order:
Thoracic Aorta
The thoracic (descending) aorta spans from the level of T4 to T12. Continuing from the aortic
arch, it initially begins to the left of the vertebral column but approaches the midline as it
descends. It leaves the thorax via the aortic hiatus in the diaphragm, and becomes the abdominal
aorta.
• Bronchial arteries: Paired visceral branches arising laterally to supply bronchial and
peribronchial tissue and visceral pleura. However, most commonly, only the paired left
bronchial artery arises directly from the aorta whilst the right branches off usually from the
third posterior intercostal artery.

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• Mediastinal arteries: Small arteries that supply the lymph glands and loose areolar tissue in
the posterior mediastinum.
• Oesophageal arteries: Unpaired visceral branches arising anteriorly to supply the oesophagus
.
• Pericardial arteries: Small unpaired arteries that arise anteriorly to supply the dorsal portion
of the pericardium.
• Superior phrenic arteries: Paired parietal branches that supply the superior portion of the
diaphragm.
• Intercostal and subcostal arteries: Small paired arteries that branch off throughout the length
of the posterior thoracic aorta. The 9 pairs of intercostal arteries supply the intercostal spaces,
with the exception of the first and second (they are supplied by a branch from the subclavian
artery). The subcostal arteries supply the flat abdominal wall muscles.

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Fig 3 – Lateral view of the thoracic aorta, with the intercostal branches
shown.

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Abdominal Aorta
The abdominal aorta is a continuation of the thoracic aorta beginning at the level of the T12
vertebrae. It is approximately 13cm long and ends at the level of the L4 vertebra. At this level, the
aorta terminates by bifurcating into the right and left common iliac arteries that supply the lower
body.
Branches
In descending order:
• Inferior phrenic arteries: Paired parietal arteries arising posteriorly at the level of T12. They
supply the diaphragm.
• Coeliac artery: A large, unpaired visceral artery arising anteriorly at the level of T12. It is also
known as the celiac trunk and supplies the liver, stomach, abdominal oesophagus, spleen,
the superior duodenum and the superior pancreas.

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• Superior mesenteric artery: A large, unpaired visceral artery arising anteriorly, just below the
celiac artery. It supplies the distal duodenum, jejuno-ileum, ascending colon and part of the
transverse colon. It arises at the lower level of L1.
• Middle suprarenal arteries: Small paired visceral arteries that arise either side posteriorly at
the level of L1 to supply the adrenal glands.
• Renal arteries: Paired visceral arteries that arise laterally at the level between L1 and L2. They
supply the kidneys.
• Gonadal arteries: Paired visceral arteries that arise laterally at the level of L2. Note that the
male gonadal artery is referred to as the testicular artery and in females, the ovarian artery.

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• Inferior mesenteric artery: A large, unpaired visceral artery that arises anteriorly at the level of
L3. It supplies the large intestine from the splenic flexure to the upper part of the rectum.
• Median sacral artery: An unpaired parietal artery that arises posteriorly at the level of L4 to
supply the coccyx, lumbar vertebrae and the sacrum.
• Lumbar arteries: There are four pairs of parietal lumbar arteries that arise posterolaterally
between the levels of L1 and L4 to supply the abdominal wall and spinal cord.

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Fig 4 – The abdominal aorta and its major
branches.

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Fig 4 – The abdominal aorta
and its major branches.

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Clinical Relevance: Aortic Aneurysm
Aortic aneurysm describes a dilation of the artery to more than 1.5 times its original size. The
abdominal component of the aorta is the most common site for aneurysmal changes.
Patients suffering with an abdominal aortic aneurysm may experience abdominal pulsations,
abdominal pain and back pain. The aneurysm may also compress nerve roots causing
pain/numbness in the lower limbs. A patient with an aortic arch aneurysm may have a hoarse
voice due to the dilation stretching the left recurrent laryngeal nerve. Patients may also not have
any symptoms at all.
Small aortic aneurysms do not usually pose a serious immediate threat. Diagnosis is made from
an ultrasound and the weakened vessel wall can be surgically replaced with a piece of synthetic
tubing. If left untreated, a large aneurysm can rupture. This is a medical emergency and often
fatal.

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Fig 6 – Aortic aneurysm, a
dilation of the vessel more
than 1.5 times the original
diameter.

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The Coeliac Trunk
The coeliac trunk is a major artery of the abdomen. It arises from the abdominal aorta,
and supplies many of the gastrointestinal viscera.
In this article, we shall look at the anatomy of the coeliac trunk – its anatomical position,
branches, anastomoses, and clinical relevance.
Anatomical Position
The coeliac trunk is the second branch of the abdominal aorta (the first branches are the paired
inferior phrenic arteries). It arises from the anterior aspect of the aorta, at the aortic hiatus of the
diaphragm (T12 level).

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Major Branches
After emerging from the aorta, the coeliac trunk extends approximately 1cm before dividing into
three major branches – left gastric, splenic and common hepatic arteries.
Of these branches, two go left and one goes to the right-hand side. Collectively, they are the
major arterial supply to the stomach, spleen, liver, gall bladder, abdominal oesophagus, pancreas
and duodenum.
Left Gastric Artery
The left gastric artery is the smallest of the three branches. It ascends across the diaphragm,
giving rise to oesophageal branches, before continuing anteriorly along the lesser curvature of
the stomach. Here, it anastomoses with the right gastric artery.

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Fig 1 – The major branches of the coeliac
trunk.

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Splenic Artery
The splenic artery arises from the coeliac trunk just inferior to the left gastric artery. It then
travels left towards the spleen, running posterior to the stomach and along the superior margin
of the pancreas. During its course, it is contained within the splenorenal ligament. It terminates
into five branches which supply the segments of the spleen.
In addition to supplying the spleen, the splenic artery also gives rise to several important vessels:
Left gastroepiploic: supplies the greater curvature of the stomach. Anastomoses with the right
gastroepiploic artery.
Short gastrics: 5-7 small branches supplying the fundus of the stomach.
Pancreatic branches: supply the body and tail of the pancreas.

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The splenic artery has a tortuous appearance (similar to the facial branch of the external carotid
artery) and thus is easily identifiable from other nearby vessels.
Common Hepatic Artery
The common hepatic artery is the sole arterial supply to the liver and the only branch of the
coeliac artery to pass to the right.
As it travels past the superior aspect of the duodenum, it divides into its two terminal branches –
the proper hepatic and gastroduodenal arteries. Each of these arteries has multiple branches and
variation in the arrangement of these branches is common.

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Proper Hepatic
The proper hepatic artery ascends through the lesser omentum towards the liver. It gives rise to:
• Right gastric: supplies the pylorus and lesser curvature of the stomach.
• Right and left hepatic: divide inferior to the porta hepatis and supply their respective lobes of
the liver.
• Cystic: branch of the right hepatic artery – supplies the gall bladder.
Gastroduodenal
The gastroduodenal artery descends posterior to the superior portion of the duodenum. Its
branches are:
• Right gastroepiploic: supplies the greater curvature of the stomach. Found between the layers
of the greater omentum, which it also supplies.
• Superior pancreaticoduodenal: divides into an anterior and posterior branch, which supplies
the head of the pancreas.

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Fig 2 – Branches of the common hepatic
artery

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Anastomoses
Stomach
The stomach is the only organ to receive arterial supply
from the three branches of the coeliac trunk (left gastric,
splenic and common hepatic arteries).
This is achieved through a system of anastomoses along
the greater (gastroepiploic arteries) and lesser (gastric
arteries) curvatures of the stomach.

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Pancreas
The pancreaticoduodenal arcade is a network of arteries that surround and supply the
head of the pancreas.
There are two main arteries – each has an anterior and posterior branch, that anastomose
(e.g. anterior to anterior) forming a ring structure:
• Superior pancreaticoduodenal– a branch of the gastroduodenal artery.
• Inferior pancreaticoduodenal – branch of superior mesenteric artery (SMA).

Fig 4 – The pancreaticoduodenal
arcade. Note: transparent
arteries are posterior to the
pictured structures
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Clinical Relevance - Disorders of the Coeliac Trunk Peptic Ulcers
Peptic ulcers in the stomach and duodenum have potential to cause significant gastrointestinal
bleeding if they erode into neighbouring arteries (usually the gastroduodenal artery).
Coeliac Trunk Compression Syndrome
The median arcuate ligament (the fibrous anchor of the diaphragm that forms the aortic hiatus)
occasionally lies anterior to the coeliac trunk, rather than its usual superior position.
This can cause compression of the coeliac trunk that may present pathologically as pain. The pain
is thought to be caused by the resulting ischemia of the abdominal organs -though it also may be
associated with compression of the coeliac ganglia.
The treatment of coeliac trunk compression syndrome is the surgical division of the median
arcuate ligament.

Fig 5 – Coeliac trunk
compression syndrome.
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Splenic Artery Aneurysm
Splenic artery aneurysms are the most common type of
visceral aneurysm, comprising around 60% of the total.
The main risk factors for their development are female
sex, multiple pregnancies, portal hypertension, and
pancreatitis or pancreatic pseudocyst formation.
Those that are symptomatic will present with a vague
epigastric or LUQ pain. Those that rupture will present
with severe abdominal pain and haemodynamic
compromise.
First line management option is endovascular repair;
this is best done with embolisation or stent grafts, once
the patient is haemodynamically stable (an open repair
may be advised in the unstable patient).

Variations
The arrangement of the branches and the order from which they arise from the coeliac trunk
can vary from person to person. This is important to remember when orientating yourself
with a specimen. Here are some examples of common variations:
• The left gastric artery often arises proximal to the bifurcation of the splenic and common
hepatic arteries. This is called a false tripod.
• The right gastric artery is occasionally seen as a branch of the common hepatic instead of
the proper hepatic artery.
• The right gastric and right hepatic arteries may arise from the SMA.
• The left hepatic artery is sometimes seen as a branch of the left gastric artery.
• The inferior phrenic arteries may arise from the coeliac trunk instead of the abdominal
aorta
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The Superior Mesenteric Artery
The superior mesenteric artery (SMA) is a major artery of the abdomen. It arises from the
abdominal aorta, and supplies arterial blood to the organs of the midgut – which spans
from the major duodenal papilla (of the duodenum) to the proximal 2/3 of the transverse
colon.
In this article, we shall look the anatomy of the superior mesenteric artery – its anatomical
position, branches, anastomoses, and clinical relevance.
Anatomical Position
he superior mesenteric artery is the second of the three major anterior branches of the
abdominal aorta (the other two are the coeliac trunk and inferior mesenteric artery). It arises
anteriorly from the abdominal aorta at the level of the L1 vertebrae, immediately inferior to the
origin of the coeliac trunk.

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After arising from the abdominal aorta, the superior mesenteric artery descends down the
posterior aspect of the abdomen. At this point, it has several important anatomical relations:
• Anterior to the SMA – pyloric part of the stomach, splenic vein and neck of the pancreas.
• Posterior to the SMA – left renal vein, uncinate process of the pancreas and inferior part of the
duodenum.
⚬ The uncinate process is the only part of the pancreas that hooks around the back of the
SMA.

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Major Branches
The superior mesenteric artery then gives rise to various branches that supply the small
intestines, cecum, ascending and part of the transverse colon (fig 1).
Fig 1 – The superior mesenteric artery
and its branches. Note: the inferior
pancreatoduodenal artery arises
more proximally, and is not visible on
this illustration.

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Inferior Pancreaticoduodenal Artery
The inferior pancreaticoduodenal artery is the first branch of the SMA. It forms anterior and
posterior vessels, which anastomose with branches of the superior pancreaticoduodenal artery
(derived from the coeliac trunk). This network supplies the inferior region of the head of the
pancreas, the uncinate process, and the duodenum.
Jejunal and Ileal Arteries
The superior mesenteric artery gives rise to numerous arteries that supply the jejunum and ileum
.
The arteries pass between the layers of the mesentery and form anastomotic arcades – from
which smaller, straight arteries (known as the “vasa recta”) arise to supply the organs (fig 2).
The jejunal blood supply is characterised by a smaller number of arterial arcades, but longer vasa
recta. In contrast, the ileal blood supply is marked by more arterial arcades with shorter vasa
recta.

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Fig 2 – Arterial supply to the jejunum and ileum of the small intestine

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Middle and Right Colic Arteries
The right and middle colic arteries arise from the right side of the superior mesenteric artery to
supply the colon:
• Middle colic artery – supplies the transverse colon.
• Right colic artery – supplies the ascending colon.
Ileocolic Artery
The ileocolic artery is the final major branch of the superior mesenteric artery. It passes inferiorly
and to the right, giving rise to branches to the ascending colon, appendix, cecum, and ileum. In
cases of appendectomy, the appendicular artery is ligated.

Clinical Relevance - Occlusion of the Superior Mesenteric
Artery
There are a number of cause of superior mesenteric artery occlusion,
including thrombosis, embolism, abdominal aortic aneurysm and aortic
dissection.
Often acute, occlusion of the SMA restricts blood flow to the midgut,
resulting in intestinal ischaemia. It is more common in the elderly, and
most usually presents with abdominal pain. The most useful investigation
in this scenario is CT scan of the abdomen.
Treatment is surgical.
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The Inferior Mesenteric Artery
The inferior mesenteric artery (IMA) is a major branch of the abdominal aorta. It supplies
arterial blood to the organs of the hindgut – the distal 1/3 of the transverse colon, splenic
flexure, descending colon, sigmoid colon and rectum.
In this article, we shall look at the anatomy of the inferior mesenteric artery – its
anatomical position, major branches and clinical correlations.
Anatomical Position
The inferior mesenteric artery is the last of the three major anterior branches of the abdominal
aorta (the other two are the coeliac trunk and superior mesenteric artery). It arises at L3, near the
inferior border of the duodenum, 3-4 cm above where the aorta bifurcates into the common iliac
arteries.

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As the artery arises from the aorta, it descends anteriorly to its parent vessel, before moving to
the left side. It is a retroperitoneal structure – situated behind the peritoneum.
Fig 1 – The origin of the inferior
mesenteric artery from the
abdominal aorta. It is the third
major branch.

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Major Branches
The branches of the inferior mesenteric artery supply the structures of the embryonic hindgut.
These include the distal 1/3 of the transverse colon, splenic flexure, descending colon, sigmoid
colon and rectum.
There are three major branches that arise from the IMA – the left colic artery, sigmoid artery and
superior rectal artery.
Left Colic Artery
The left colic artery is the first branch of the IMA. It supplies the distal 1/3 of the transverse colon
and the descending colon. After arising from its parent artery, it travels anteriorly to the psoas
major muscle, left ureter and left internal spermatic vessels, before dividing into ascending and
descending branches:

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• Ascending branch – crosses the left kidney anteriorly, before entering the mesentery of the
transverse colon, moving superiorly. It supplies the distal 1/3 of the transverse colon, and the
upper aspect of the descending colon.
• Descending branch – moves inferiorly to supply the lower part of the descending colon. It
anastomoses with the superior sigmoid artery.
Sigmoid Arteries
The sigmoid arteries supply the descending colon and the sigmoid colon. There are typically 2-4
branches, with the uppermost branch termed the superior sigmoid artery. They run inferiorly,
obliquely and to the left, crossing over the psoas major, left ureter and left internal spermatic
vessels.

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Superior Rectal Artery
The superior rectal artery is a continuation of the inferior mesenteric artery, supplying the
rectum. It descends into the pelvis, crossing the left common iliac artery and vein.
At the S3 vertebral level, the artery divides into two terminal branches – one supplying each side
of the rectum. Within the walls of the rectum, smaller divisions of these branches eventually
communicate with the middle and inferior rectal arteries.

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Fig 2 – The major branches of the IMA supplying the sigmoid colon and
rectum.

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Clinical Relevance - Left Hemicolectomy
A left hemicolectomy is the surgical resection (removal) of the descending colon. It can be
performed for a variety of reasons such as removal of colon cancer, treatment of diverticulitis,
inflammatory bowel disease or trauma.
During the procedure, the surgeon must dissect the branches of the inferior mesenteric artery.
They do this by shining a light through the mesentery to identify the IMA and inferior mesenteric
vein (note that the IMV follows a different course than the IMA). They then trace the artery back
to the aorta and divide it proximally.

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Anastomoses
There are two major anastomoses of the IMA, both involving a union with branches of the
superior mesenteric artery:
• Marginal artery (of Drummond) – forms a continuous arterial circle along the inner border of
the colon. Straight vessels (vasa recta) arise from the artery to supply the colon. It is formed
by the union of several branches; the ileocolic, right colic and middle colic of the SMA and left
colic and sigmoid branches of the IMA.
• Arc of Riolan – anastomosis between the middle colic branch of SMA and the left colic branch
of IMA. It is less common than the marginal artery, and indeed its existence has been
questioned by some surgeons.
The splenic flexure can be described as a watershed area – a term used when an area has dual blood supply from
the most distal branches of two large arteries. Whilst this has the advantage of being more resistant to ischaemia
if one of the arteries becomes occluded, it makes the area more sensitive to systemic hypoperfusion.

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Fig 3 – The marginal artery of
Drummond.

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Clinical Relevance - Horseshoe Kidney
Horseshoe kidney is a congenital disorder where the kidneys fuse together, forming a
horseshoe shape. It affects 1/400, and is more common in males.
During embryonic development, the kidneys ascend from the pelvis to their position in the
abdomen. In a patient with horseshoe kidney, the fused kidney becomes hooked underneath
the inferior mesenteric artery, and is stuck in the lower abdomen.
It does not require any treatment, and is often asymptomatic. However, complications can
occur from the poor drainage of the kidney, such as hydronephrosis, renal stones, and
infection.

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Venous Drainage of the Abdomen
There are two venous systems that drain abdominal structures – the portal venous system
and the systemic venous system. The portal system transports venous blood to the liver
for processing, whilst the systemic venous system returns blood to the right atrium of the
heart.
In this article, we shall consider the anatomy of these two venous systems – the major
vessels involved, their anatomical course, and their tributaries.

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The systemic venous system transports deoxygenated blood to the right atrium of the
heart. The major vessel in this system is the inferior vena cava.
Inferior Vena Cava
The inferior vena cava is the common convergence of venous drainage from all structures
below the diaphragm. It is located on the posterior abdominal wall; anteriorly to the
vertebral column and to the right of the abdominal aorta.
The vessel is formed by the union of the common iliac veins at the L5 vertebral level. It
ascends superiorly, and leaves the abdomen by piercing the central tendon of the
diaphragm at the T8 level (the caval hiatus). Within the thorax, the inferior vena cava
drains into the right atrium of the heart.
Systemic Venous
System

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During its long course, the inferior vena cava shares an anatomical relationship
with numerous abdominal structures – including the right common iliac artery, the root
of the mesentery, the head of the pancreas, the bile duct, the portal vein and the liver.
Tributaries
The inferior vena cava is responsible for the venous drainage of all structures below the
diaphragm. It receives tributaries from:
• Common iliac veins – formed by the external and internal iliac veins. They drain the lower
limbs and gluteal region.
• Lumbar veins – drain the posterior abdominal wall.
• Renal veins – drain the kidneys, left adrenal gland and left testis/ovary.

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• Right testicular or ovarian vein – drains the right testes in males and the right
ovary in females (the left testicular or ovarian vein drains into the left renal vein).
• Right suprarenal vein – drains the right adrenal gland (the left adrenal vein drains into the left
renal vein).
• Inferior phrenic veins – drain the diaphragm.
• Hepatic veins – drain the liver.
There are no tributaries from the spleen, pancreas, gallbladder or the abdominal part of the GI
tract – as these structures are first drained into the portal venous system. However, venous return
from these structures ultimately enters the inferior vena cava via the hepatic veins (after being
processed by the liver).

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Fig 1.0 – The inferior vena cava and
major tributaries. Note how the left
adrenal vein and left testicular vein
empty into the left renal vein.

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Portal Venous System
The portal system carries venous blood (rich in nutrients that have been extracted from food) to
the liver for processing.
The major vessel of the portal system is the portal vein. It is the point of convergence for the
venous drainage of the spleen, pancreas, gallbladder and the abdominal part of the
gastrointestinal tract. The portal vein is formed by the union of the splenic vein and the superior
mesenteric vein, posterior to the neck of the pancreas, at the level of L2.
As it ascends towards the liver, the portal vein passes posteriorly to the superior part of the
duodenum and the bile duct. Immediately before entering the liver, the portal vein divides into
right and left branches which then enter the parenchyma of the liver separately.

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Tributaries
The portal vein is formed by the union of the splenic vein and superior mesenteric vein. It
receives additional tributaries from:
• Right and left gastric veins – drain the stomach.
• Cystic veins – drains the gallbladder.
• Para-umbilical veins – drain the skin of the umbilical region.
Splenic Vein
The splenic vein is formed from a variety of smaller vessels as they leave the hilum of the spleen.
Unlike the splenic artery, the splenic vein is straight and it maintains contact with the body of the
pancreas as it crosses the posterior abdominal wall. As it reaches the neck of the pancreas, the
splenic vein joins the superior mesenteric vein to form the portal vein.

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Tributaries
Tributaries to the splenic vein include:
• Short gastric veins – drain the fundus of the stomach.
• Left gastro-omental vein – drains the greater curvature of the stomach.
• Pancreatic veins – drain the pancreas.
• Inferior mesenteric vein – drains the colon.
The inferior mesenteric vein drains blood from the rectum, sigmoid colon, descending colon and
splenic flexure. It begins as the superior rectal vein and ascends, receiving tributaries from the
sigmoid veins and the left colic veins. As it ascends further it passes posteriorly to the body of the
pancreas and typically joins the splenic vein.

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Fig 2 – The hepatic portal venous system.

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Superior Mesenteric Vein
The superior mesenteric vein drains blood from the small intestine, cecum, ascending colon and
transverse colon. It begins in the right iliac fossa, as a convergence of the veins draining the
terminal ileum, cecum and appendix. It ascends within the mesentery of the small intestine, and
then travels posteriorly to the neck of the pancreas to join the splenic vein.
Tributaries
• Tributaries to the superior mesenteric vein include:
• Right gastro-omental vein – drains the greater curvature of the stomach.
• Anterior and posterior inferior pancreaticoduodenal veins – drain the pancreas and
duodenum.
• Jejunal vein – drain the jejunum.
• Ileal vein – drain the ileum.

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• Ileocolic vein – drains the ileum, colon and cecum.
• Right colic vein – drains the ascending colon.
• Middle colic vein – drains the transverse colon.
Many of these tributaries are formed as an accompanying vein for each branch of the superior
mesenteric artery.

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Clinical Relevance – Porto- Systemic Anastomoses
A porto-systemic anastomosis is a connection between the veins of the portal venous system,
and the veins of the systemic venous system. The major sites of these anastomoses include:
• Oesophageal – Between the oesophageal branch of the left gastric vein and the
oesophageal tributaries to the azygous system.
• Rectal – Between the superior rectal vein and the inferior rectal veins.
• Retroperitoneal – Between the portal tributaries of the mesenteric veins and the
retroperitoneal veins.
• Paraumbilical – Between the portal veins of the liver and the veins of the anterior
abdominal wall.

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When blood flow through the portal system is obstructed
(e.g due to cirrhosis, portal vein thrombosis, or external
pressure from a tumour), the pressure within portal
system increases. A portal venous pressure in excess of
20mmHg is defined as portal hypertension.
In portal hypertension, blood may be re-directed
through the porto-systemic anastomoses (as these are
now under a lower pressure). If a large volume of blood
passes through these anastomoses over a long period of
time, the veins around the anastomosis can become
abnormally dilated – known as varices. Rupture of
oesophageal or rectal varices can result in fatal blood
loss.
Fig 3 – Endoscopic appearance of oesophageal
varices. They can undergo rupture, leading to
large volumes of blood loss.

Abdominal Anatomy for MRCEM PRIMARY EXAM

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