Anatomy of Abdomen


Blood supply
arteries of abdomen
all arteries of abdomen
blood flow in abdomen

(I) Abdominal aorta:

  • Lower border of T12 – lower border of L4 (aortic hiatus to bifurcation)
  • Travels down posterior wall of abdomen
  • Runs on the left and parallel to IVC
  • At L4 bifurcates


  • Anterior – Lesser omentum, stomach, pancreas
  • Posterior – Vertebral column, lumbar veins
  • Right – IVC, azygos vein, cisterna chyli, right crus diaphragm
  • Left – Left crus diaphragm, ascending duodenum, small intestines


  • Rupture of abdominal aortic aneurysm – deep pain in abdomen, back pain, hemoperitoneum (blood in peritoneal cavity) – leads to hemorrhagic shock – rapid death

(II) Celiac trunk:

  • 1st branch of abdominal aorta – T12
  • Divides into 3 branches

(III) Superior mesenteric artery:

  • 2nd branch of abdominal aorta – L1
  • Posterior to neck of pancreas
  • Pass between pancreas head and uncinate process
  • Terminates in right iliac fossa as ileocolic artery

(IV) Inferior mesenteric artery:

  • 3rd branch of abdominal aorta – L3
  • Posterior to left psoas major
  • Terminates as superior rectal artery


  • Peptic ulcers – erode gastroduodenal artery, leads to gastrointestinal bleeding
  • Celiac trunk compression syndrome – due to median arcuate ligament, leads to ischemia (median arcuate ligament connects right and left crura of diaphragm)
  • Splenic artery aneurysm
  • Left hemicolectomy – surgical removal of descending colon – dissect branches of IMA and IMV


Venous drainage of abdomen
all veins of abdomen
venous course in abdomen
portosystemic anastomoses

(I) IVC:

  • Formed by left and right common iliac veins at L5
  • Ascends on right of vertebral column and aorta
  • Anterior to right psoas major
  • Grooves liver
  • Enters through diaphragm at T8 – caval opening


  • Anterior – Head of pancreas, epiploic foramen, right and caudate lobe liver
  • Posterior – Right psoas major, right crus diaphragm, Lower lumbar vertebrae
  • Right – Right kidney, right lobe liver
  • Left – Abdominal aorta

(II) IVC and SVC communication sites:

1. Thoracoepigastric – connects lateral thoracic vein (axillary vein – SVC) and superficial epigastric vein (femoral vein – IVC)

2. Superior epigastric (internal thoracic – SVC) and inferior epigastric (external iliac – IVC)

3. Azygos venous system

4. Vertebral venous plexus – Lumbar veins (IVC) and posterior intercostal veins (SVC)

(III) Portal vein:

  • Formed from superior mesenteric vein and splenic vein – behind neck of pancreas
  • Before reaching liver, portal vein divides into right and left branches – divides in to smaller venous branches
  • Drains into hepatic sinusoids (supply blood to liver)


  • Portal hypertention – obstruction of blood flow through portal system, blood redirected through portosystematic anastomosis, veins become dilated – varices and hemorrhoids
  • Infection of portal vein (pylephlebitis)


(I) Nerves of abdominal wall: Somatic – Parietal peritoneum and skin

1. Anterolateral abdominal wall: Anterior rami of:

  • T7-T9 – Skin superior to umbilicus
  • T10 – Skin around umbilicus
  • T11 – Skin inferior to umbilicus
  • T12/Subcostal – Skin inferior to umbilicus
  • L1 – Iliohypogastric and ilioinguinal – Skin inferior to umbilicus

2. Posterior abdominal wall:

  • T12 – subcostal
  • Lumbar (L1-L5): Iliohypogastric and ilioinguinal (L1), Gentitofemoral (L1-L2), Lateral cutaneous femoral (L2-L3), Femoral (L2-L4), Obturator (L2-L4), Lumbosacral trunk (L4-L5)

nerves on the posterior abdominal wall
lumbar plexus

(II) Nerves of GIT: Visceral – Abdominal viscera and visceral peritoneum

Nerves of GIT: sympathetic and parasympathetic
celiac ganglion, superior mesenteric ganglion, inferior mesenteric ganglion, pelvic splanchnic

Sympathetic: vasoconstrict blood vessels, decrease peristalsis and digestion, close sphincters of GIT

Parasympathetic: vasodilate blood vessels, increase peristalsis and digestion, stimulate insulin production


  • If a sympathetic nerve is supplying a thoracic viscera – Synapse occurs in sympathetic chain
  • If a sympathetic nerve is supplying an abdominal viscera – No synapse, but passes through the chain and synapses at the celiac ganglion, SMG or IMG

1. Presynaptic fibers T5-T9 ⇒ Greater splanchnic nerve – Sympathetic

  • Synapse in celiac ganglion
  • Post synaptic fibers – pass in celiac plexus – towards branches of celiac trunk and supplies foregut organs

2. Presynaptic fibers T10-T11 ⇒ Lesser splanchnic nerve – Sympathetic

  • Synapse in SMG
  • Post synaptic fibers – pass in SM plexus – towards branches of SMA and supplies midgut organs

3. Presynaptic fibers T12 ⇒ Least splanchnic nerve – Sympathetic

  • Synapse in SMG
  • Post synaptic fibers – pass in SM plexus – towards branches of SMA and supplies midgut organs

4. Presynaptic fibers L1-L3 ⇒ Lumbar splanchnic nerve – Sympathetic

  • Synapse in IMG
  • Post synaptic fibers – pass in IM plexus – towards branches of IMA and supplies hindgut organs

5. Vagus nerve – Parasympathetic

  • Presynaptic fibers of vagus – through celiac plexus – synapses at small ganglion of the foregut organ
  • Presynaptic fibers of vagus – through SM plexus – synapses at small ganglion of the midgut organ

6. Presynaptic S2,S3,S4 – Pelvic splanchnic nerve – Parasympathetic

  • Run in inferior hypogastric plexus – ascend to superior hypogastric plexus – then to inferior mesenteric plexus – along branches of IMA
  • Synapse at small ganglion of hindgut organ

Blood and nerve supply of foregut, midgut and hindgut organs

Foregut organs: Esophagus, stomach, 1st part duodenum, pancreas, liver, gallbladder

  • Artery – Celiac trunk
  • Nerve – Greater splanchnic, vagus

Midgut organs: Rest of duodenum, jejunum, ilium, cecum, appendix, ascending colon, proximal 2/3 transverse colon

  • Artery – SMA
  • Nerve – Lesser splanchnic, least splanchnic and vagus

Hindgut organs: Rectum, upper anal canal, descending colon, sigmoid colon, distal 1/3 transverse colon

  • Artery – IMA
  • Nerve – Lumbar splanchnic, pelvic splanchnic


Longitudinal section of abdomen:

Longitudinal section of abdomen

Supracolic and infracolic connected by paracolic gutters – drain fluid such as pus or bile to outer margins of colon (Clinical – spread infection, tumor deposits from or to pelvis)

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supracolic compartment, infracolic compartment

Organs are covered by visceral peritoneum. Between parietal and visceral peritoneum is peritoneal fluid (contains electrolytes, antibodies, WBC, glucose)

Clinical: Ascites – fluid accumulation

Regions of abdomen:

Regions of abdomen: 9 divisions


  • Pain location, surgical procedures
  • Abdominal hernias:
  1. Internal – hiatus of diaphragm, epiploic foramen
  2. External – inguinal, femoral, obturator

Anterior abdominal wall


  • Skin
  • Superficial fascia:
  1. Above umbilicus – single sheet of connective tissue
  2. Below umbilicus – fatty Camper’s fascia then membranous Scarpe’s fascia
  • Muscles: enclosed in deep investing fascia
  1. External oblique
  2. Internal oblique
  3. Transverse abdominis
  • Fascia transversalis
  • Extraperitoneal fatty areolar tissue
  • Parietal peritoneum


  • In the centre is rectus muscle
  • Scarpe’s fascia continues as Colle’s and Darto’s fascia and is inferiorly attached to fascia lata below inguinal ligament. Therefore when penile urethra injured in men, urine escapes urethra to scrotum and spreads in lower abdominal wall but not to thigh.


  • Contain and protect abdominal contents
  • Increase intraabdominal pressure in micturition, defecation, coughing, sneezing and parturition
  • Cause trunkal flexion
  • Contribute to venous return

Blood supply:

  • Internal thoracic – Superior epigastric, musculophrenic
  • Abdominal aorta – Posterior intercostal, subcostal
  • External iliac – Inferior epigastric, deep circumflex iliac
  • Femoral – Superficial circumflex iliac, superficial epigastric

Nerves: Written in nerves


  • Superficial:
  1. Superior to umbilicus – Anterior axillary and parasternal
  2. Inferior to umbilicus – Superficial inguinal
  • Deep: External iliac, lumbar nodes

Anterior Abdominal wall muscles:

Anterior abdominal wall muscles


  • Abdominal incision/ Laparotomy – most common is midline incision along linea alba from xiphoid process to umbilicus to pubic symphysis
  • Urinary extravasation – penile urethra injured in men, urine escapes urethra to scrotum and spreads in lower abdominal wall but not to thigh
  • Venous engorgement – flow in SVC or IVC obstructed, leads to collateral flow
  • Ascites
  • Caput medusae – engorged superficial epigastric veins
  • Liposuction

Rectus sheath

Rectus sheath

Posterior abdominal wall


  1. Fascia transversalis
  2. Psoas major fascia
  3. Thoracolumbar fascia – 3 layers

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  • Psoas abscess – caused by lumbar tuberculosis, infects psoas sheath
  • Psoas sign

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Inguinal canal

Superior and parallel to inguinal ligament

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Inguinal canal boundaries

Contents: Ilioinguinal nerve, genitofemoral nerve, round ligament (females), spermatic cord (males)

Inguinal triangle of Hesselbach

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boundaries of hesselbach triangle


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Closed sac except in females where infundibulum opens

Layers: Parietal and visceral

Intraperitoneal organs: Stomach, spleen, liver, transverse colon

Retroperitoneal organs: Primary (retro since developed – KER) and secondary (become retro later – SADPUC)

Retroperitoneal viscera:

  • S – Suprarenal glands
  • A – Aorta and IVC
  • D – Duodenum (2nd part)
  • P – Pancreas
  • U – Ureter
  • C – Colon (ascending and descending)
  • K – Kidney
  • E – Esophagus
  • R – Rectum


  • Median umbilical ligament (allantoic duct) – urinary bladder apex to umbilicus
  • 2 medial umbilical ligaments (umbilical arteries)
  • 2 lateral umbilical ligaments – cover inferior epigastric artery

NB: Umbilical vein – becomes ligamentum teres of liver

Mesenteries: Fold of visceral peritoneum that attatches intraperitoneal organs to posterior abdominal wall. Contains nerves, vessels, lymph nodes and fat


  1. Greater omentum – From greater curvature stomach and proximal duodenum ⇒ to infront of small intestines ⇒ Reflects and ascends to transverse colon

Greater omentum

Contains: Nerves, vessels, lymph nodes and fat

Parts: Gastrosplenic ligament, gastrophrenic ligament, gastrocolic ligament


  • Infection and wound isolation
  • Limit spread of intraperitoneal infections
  • Immunity – macrophages, lymphocytes etc
  • Mobility
  • Insulation

2. Lesser omentum – From lesser curvature stomach to liver

Parts: Hepatogastric ligament (right and left gastric arteries), hepatoduodenal ligament (Common bile duct, portal vein, hepatic artery)

Peritoneal cavity:

Epiploic foramen – Relations:

  • Superior – Caudate lobe liver
  • Inferior – 1st part duodenum
  • Anterior – Hepatoduodenal ligament
  • Posterior – IVC


  • Internal hernia
  • Accumulation of blood (ruptured spleen), bile (bile duct) or fecal matter (intestines)
  • Peritonitis – infection due to bacterial contamination



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Impressions on liver:

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posterior and inferior surfaces of liver

Position: Right 1/4, deep to ribs 7-11

Surfaces: Diaphragmatic and visceral


  • Anterior: Diaphragm, ribcage, falciform ligament
  • Posterior: Right kidney and adrenal, gall bladder, esophagus, stomach
  • Superior: Diaphragm
  • Inferior: Gall bladder

Support structures: Falciform ligament, coronary ligament, ligamentum teres, triangular ligament, hepatoduodenal ligament, lesser omentum and hepatic veins

Blood supply: Right and left hepatic arteries – segmental branches

Venous: Hepatic portal vein – drains to hepatic sinusoids and so to IVC

Nerves: Sympathetic – Greater splanchnic, Parasympathetic – Vagus, right phrenic

Lymphatics: Hepatic, left gastric nodes

Hepatic recesses: 

  • Right and left subphrenic spaces – between diaphragm and liver
  • Subhepatic space – between inferior surface liver and transverse colon
  • Morrison’s pouch/ hepatorenal – between liver and right kidney

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Functional divisions of liver:

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Couinaud's segments


  • Hepatic lobectomies
  • Rupture of liver – fractured rib, hemorrhage
  • Liver trauma – tearing of hepatic veins from IVC
  • Hepatomegaly – enlarged liver – due to infection, tumours or metabolic disorder
  • Liver cirrhosis – health tissue replaced by scar tissue, organ will start to fail, blood cannot easily flow in portal vein
  • Liver biopsy – small needle inserted in liver to collect tissue sample
  • Jaundice


Location: Between right and left lobes, inferior surface of liver

Biliary tree:

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  • Anterior – Inferior surface liver
  • Posterior – Transverse colon, proximal duodenum
  • Superior – Liver
  • Inferior – Biliary tree

Blood: Cystic artery

Venous: Cystic vein, hepatic sinusoids

Nerves: Sympathetic – Greater splanchnic, Parasympathetic – Vagus, right phrenic

Lymph: Hepatic nodes


  • Mobile gallbladder – only attached to cystic duct, risk of torsion
  • Cholecystectomy
  • Gall stones
  • Biliary colic – gall stones block bile duct
  • Cholecystitis – inflammation



Image result for spleen impressions

Surfaces: Diaphragmatic and visceral


  • Anterior: Stomach
  • Posterior: Left kidney and adrenal, ribs 9-11
  • Inferior: Left colic flexure

Support structures:

  • Gastrosplenic ligament (short gastric vessels) – great curvature to spleen
  • Splenorenal ligament (Splenic vessels) – spleen to left kidney
  • Phrenicocolic ligament – diaphragm to left colic flexure

Blood supply: Splenic artery – 5 segmental arteries

Venous: Splenic vein

Nerves: Sympathetic – Greater splanchnic, Parasympathetic – Vagus, right phrenic

Lymphatics: Celiac nodes


  • Rupture of spleen – fractured rib, intraperitoneal hemorrhage
  • Splenectomy
  • Splenomegaly
  • Accessory spleen
  • Splenic biopsy


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  • Anterior – Left lobe liver
  • Posterior – Lesser sac, spleen, left kidney and adrenal, splenic artery, pancreas, aorta
  • Inferior – Transverse colon, left colic flexure

Blood supply:

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Nerves: Sympathetic – Greater splanchnic, Parasympathetic – Vagus, right phrenic


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  • Esophageal varices – portal hypertension
  • Pyrosis (heart burn) – due to gastroesophageal reflex disorder (stomach acid flows to esophagus)
  • Gastroesophageal reflex disorder – hiatus hernia, delayed gastric emptying, dysfunction of lower esophagus sphincter
  • Hiatus hernia – part of stomach protrudes through esophageal hiatus in diaphragm
  • Pylorospasm – closure of pylorus due to muscle spasm, due to pyloric ulcers
  • Gastrectomy
  • Gastric ulcers – erode arteries nearby


Image result for parts of pancreas


Relations to parts of stomach
stomach relations

Blood supply: Greater pancreatic artery (from splenic artery), Superior and inferior pancreaticoduodenal artery

Nerves: Sympathetic – Greater splanchnic, Parasympathetic – Vagus, right phrenic

Lymphatics: Pancreaticosplenic, pancreaticoduodenal


  • Blocked hepatopancreatic ampulla – gallstone
  • Pancreatitis
  • Pancreatic ectomy
  • Rupture
  • Cancer


From pylorus to duodenojejunal junction

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Relation to duodenum
parts of duodenum relations

Support structures: Hepatoduodenal ligament, ligament of Trietz


Image result for duodenum recesses

Blood supply: Superior and inferior pancreaticoduodenal, right gastroepiploic

Nerve: Sympathetic – Greater and lesser splanchnic, Parasympathetic – Vagus

Lymphatics: Pancreaticoduodenal nodes, superior mesenteric nodes


  • Duodenal ulcers – erode gastroduodenal artery – hemorrhage
  • Paraduodenal hernia – intestinal loops

Jejunum and ileum

From duodenojejunal junction to ileocecal junction

Image result for difference between jejunum and ileum anatomy

Blood supply: SMA and vasa recta

Nerves: Lesser splanchnic, least splanchnic and vagus

Clinicals: Ischemia of intestine – occlusion of vasa recta by embolus

Large intestine

From ileocecal valve in right iliac fossa to anal orifice

Image result for parts of large intestines

NB: Ascending colon has no mesentary


Large intestine relations
parts of large intestine relations

Blood supply:

Blood supply of large intestine


  • Lesser splanchnic, least splanchnic and vagus – Cecum, appendix, ascending colon, proximal 2/3 transverse colon
  • Lumbar splanchnic and pelvic splanchnic – Distal 1/3 transverse, descending and sigmoid coloc

Lymphatics: Epicolic and paracolicdrain into superior and inferior mesenteric nodes


  • Colitis
  • Colectomy
  • Ileostomy – artificial opening of ileum through abdominal wall
  • Colonoscopy
  • Diverticula – pouches form on wall of colon (usually sigmoid) – old people
  • Volvulus sigmoid- sigmoid colon twists on sigmoid mesocolon – bowel obstruction

Difference between small and large intestine:

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Location: Right iliac fossa, opens in cecum


  • Anterior – Greater omentum
  • Posterior – Psoas major
  • Superior – Ileum, mesoappendix (portion of the mesentery connecting the ileum to the appendix)
  • Left – Sigmoid colon
  • Right – Paracolic gutter, ascending colon


Image result for appendix positions

Blood supply: Appendicular artery and vein

Nerves: Lesser splanchnic, least splanchnic and vagus

Lymphatics: Superior mesenteric


  • Appendicitis
  • Appendectomy
  • Psoas test


Are 3 vertebrae long

Coverings: Superficial to deep

Pararenal fat ⇒ Renal fascia (enclose kidney and suprarenal glands) ⇒ Perirenal fat ⇒ Fibrous renal capsule

Support structures: Splenorenal ligament



Kidney's relations, anterior


Kidney's relations posterior

Blood supply:

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Blood flow in kidney

Nerves: Lesser splanchnic, least splanchnic and vagus

Lymphatics: Lumbar nodes


  • Perinephric abscess – pus around kidney
  • Pelvic kidney
  • Horseshoe kidney
  • Renal agenesis
  • Renal hypoplasia
  • Kidney stones/renal calculi – formed in kidney or renal pelvis, may pass through ureter into bladder
  • Renal transplant – to lower abdomen, renal vessels connected to recipient external iliac vessels, ureter sutured into urinary bladder
  • Nephrectomy
  • Floating kidney – abnormal condition in which the kidney drops down into the pelvis when the patient stands up

Suprarenal glands

Cortex (mesoderm) and medulla (ectoderm – neural crest). Fatty tissue between kidney and suprarenal gland, covered in renal fascia.



  • Anterior – Right lobe liver
  • Posterior – Right crus diaphragm
  • Superior – Liver


  • Anterior – Stomach, pancreas, spleen
  • Posterior – Left crus diaphragm
  • Superior – Spleen

Blood supply: Superior, middle and inferior suprarenal

Venous: Right and left suprarenal

Nerves: Greater splanchnic, lesser splanchnic

Lymphatics: Lumbar nodes

Right and left difference:

Image result for right and left suprarenal gland difference

Right – Triangular shape, loosely attached to superior pole kidney

Left – Cresent shape, superior and middle border can extend to renal hilum


  • Tumor of medulla
  • Addison’s disease – low cortisol and aldosterone
  • Cushing’s syndrome – elevated cortisol



  • Continuation of renal pelvis
  • Posterior to renal vessels
  • Anterior to psoas major
  • Gonadal vessels cross over it from medial to lateral
  • Cross infront of common iliac bifurcation
  • Opposite sacroiliac joint
  • Opposite ischial spine, curves anteromedial to open into posterior superior part of bladder
  • Runs an oblique 2cm course in urinary bladder wall – forms valve like mechanism

Blood supply:

Blood supply of ureter

Nerves: Renal plexus, superior hypogastric plexus, T11-L2

Lymphatics: Lumbar, common iliac, external iliac, internal iliac


Relation of ureter in male and female in abdomen and pelvis, right and left


  • Retrocanal ureter – Right ureter passes posterior to IVC, disturbs drainage from right kidney
  • Kidney stones – Obstruct urine flow


1. Lumbar triangle:

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inferior lumbar triangle (petit's triangle) borders
superior lumbar triangle (grvnfeltt-lesshaft) borders

2. Calot’s triangle/Cystohepatic triangle:

Content: Cystic artery

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3. Triangle of doom:

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  • External iliac vessels
  • Deep circumflex iliac vein
  • Femoral nerve
  • Genital branch of genitofemoral nerve

Clinicals: Inguinal hernia – nerves damaged when repairing a hernia by sutures or staples

4. Triangle of pain:

triangle of pain boundaries

5. Triangle of safety:

For intercostal catheter placement

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6. Modification of fascia transversalis:

  • Femoral sheath and ring – anterior
  • Deep inguinal ring – posterior
  • Internal spermatic fascia in testis

7. Mcburney’s point:

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8. Mechanisms to prevent inguinal hernia:

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These are summarized notes from various sources, mainly TeachMeAnatomy and Wikipedia