T3 L5: Posterior abdominal wall

• Why are the lumbar vertebrae larger than the thoracic vertebrae?

  they need to support the weight of the upper body
• What are the bones of the posterior abdomen?

  ribs 11 and 12

  lumbar vertebrae L1-L5

  Sacrum

  Ilia

  
• What is the iliopubic eminence?

  where ileum meets pubis

  
• What are the muscles of the posterior abdomen?

  1. Diaphragm
  2. Psoas minor (only in 50% of individuals)
  3. Psoas major
  4. Iliacus (lines iliac fossa)
  5. Iliopsoas (where iliacus and psoas muscles meet through inguinal ligament)
  6. Quadratus lumborum

  
• What are the characteristics of Quadratus Lumborum muscle?

  Origin: Iliolumbar ligament and iliac crest

  Insertion: transverse process (L1-L4), rib 12

  Action: depress and stabilise rib 12, lateral trunk flexion

  Innervation: T12-L4

  
• What are the characteristics of Iliacus muscle?

  Origin: iliac fossa

  Insertion: lesser trochanter of femur

  Action: flexion of thigh at hip

  Innervation: femoral nerve (L2-L4)

  
• What are the characteristics of Psoas major?

  Origin: vertebral bodies T12-L5, transverse processes L1-L5

  Insertion: lesser trochanter of femur

  Action: flexion of thigh at hip

  Innervation: L1-L3

  
• What are the characteristics of Psoas minor?

  Origin: vertebral bodies T12-L1

  Insertion: iliopubic eminence

  Action: weak flexion of vertebral column (tilt pelvis upwards slightly)

  Innervation: L1

  
• What are the characteristics of the abdominal aorta?

  thoracic aorta becomes abdominal aorta at diaphragm when it passes through aortic hiatus - level T12

  bifurcates into common iliac arteries at L4

  lies left of inferior vena cava

  
• What are the direct branches of the abdominal aorta?

  1. inferior phrenic arteries (T12) - supply inferior diaphragm
  2. coeliac trunk (T12)
  3. Middle suprarenal arteries (L1)
  4. Superior mesenteric (L1)
  5. Renal arteries (L1-L2)
  6. Gonadal (testicular/ovarian) arteries (L2)
  7. Inferior mesenteric (L3)
  8. Lumbar arteries (L1-L4) - supply posterior abdominal wall
  9. Median sacral (L4)

  
• What are the paired branches directly coming off the abdominal aorta?

  1. inferior phrenic arteries (T12)
  2. middle suprarenal arteries (L1)
  3. Renal arteries (L1-L2)
  4. Gonadal arteries (L2)
  5. Lumbar arteries (L1-L4)

  
• What are the unpaired branches directly coming off the abdominal aorta?

  1. Coeliac trunk (T12)
  2. Superior mesenteric (L1)
  3. Inferior mesenteric (L3)
  4. Median sacral (L4)

  
• What are the characteristics of the inferior vena cava?

  formed by union of common iliac veins at L5

  leaves abdomen through diaphragm (caval hiatus) at T8

  
• What are the tributaries of the inferior vena cava?

  1. Inferior phrenic veins
  2. Hepatic veins x3
  3. Right suprarenal vein
  4. Renal veins
  5. Right gonadal vein
  6. Lumbar veins
  7. Ascending lumbar veins (* not directly off vena cava, tributary of azygos system)

  
• What are the branches of the lumbar plexus?

  somatic

  formed within substance of Psoas major muscle

  L1 - L4

  motor and sensory innervation of the thigh, pelvis, abdominal wall, parietal peritoneum

  1. Subcostal T12(*spinal nerve, not part of plexus!)
  2. Iliohypogastric L1
  3. Ilioinguinal L1
  4. Genitofemoral L1-L2

  
• What are the three categories of abdominal pain?

  1. Somatic: well localised, sharp
  2. Visceral: poorly localised & dull, sensory nerves follow autonomic nerves
  3. Referred: felt elsewhere, at dermatome with shared spinal roots

  
• How is the sympathetic and visceral afferent innervation of the abdomen?

  1. Greater splanchnic nerve (T5-9) - coeliac ganglia (Foregut)
  2. Lesser splanchnic nerve (T10-11) - superior mesenteric ganglia (Midgut)
  3. Least splanchnic nerve (T12) - kidneys
  4. Lumbar splanchnic nerve (L1-L2) (Hindgut)

  
• Where is abdominal pain referred to?

  Pain from foregut → epigastric region

  Pain from midgut → umbilical region

  Pain from hindgut → hypogastric region

  sensory input from visceral organs is interpreted by the brain as originating from one of the midline dermatomes (due to embryological origin)

  
• Example: where is the pain of appendicitis referred to?

  The appendix is a part of the mid gut.

  Sympathetic innervation for the appendix comes from the Lesser splanchnic nerve.

  The Lesser splanchnic nerve has spinal roots T10-T11.

  Visceral afferent nerve fibres travel with the Lesser splanchnic nerve to T10-T11 spinal levels.

  Appendicitis results in referred pain to the umbilical region.

  
• What is McBurney's point?

  lateral 1/3 of line from ASIS to umbilicus.

  
• When does pain in McBurney's point develop?

  when parietal peritoneum is irritated (in appendicitis) as has somatic innervation
• Where would referred pain from the gallbladder be felt?

  shoulder

  gallbladder closely related to diaphragm

  which is innervated by phrenic nerve (C3,4,5)

  
• How is the lymphatic drainage of the organs of the abdomen?

  Towards the cisterna chyli:

  Foregut → celiac nodes

  Midgut → superior mesenteric nodes

  Hindgut → inferior mesenteric nodes

  Kidney & suprarenal → Lateral aortic nodes

  Rectutm & anal canal → Common iliac nodes

  Anal canal → superficial inguinal nodes
• How is the lymphatic drainage labelled, from inferior to superior?

  1. Superficial inguinal lymph nodes
  2. Common iliac lymph nodes
  3. inferior mesenteric lymph nodes (hindgut)
  4. Lateral aortic
  5. Left lumbar trunk
  6. Right lumbar trunk
  7. intestinal trunk
  8. Cisterna chyli
  9. Superior mesenteric lymph nodes (midgut)
  10. Coeliac lymph nodes (Foregut)
  11. Inferior phrenic lymph nodes