Anatomy of the posterior abdominal wall

Question 1

What is the posterior abdominal wall?

Answer 1

It is an Osseo-musculo-fascial extension from the last rib to the pelvic brim, anteriorly it is related to the retroperitoneal organs and the parietal peritoneum

Question 2

What are the contents of the posterior abdominal wall?

Answer 2

1) Bones

2) Muscles (Psoas minor, psoas major, iliacus, quadratus lamborum)

3) Abdominal aorta

4) Inferior vena cava

5) Nerves

6) Viscera

7) Lymphatic drainage

Question 3

What are the bones of the posterior abdominal wall?

Answer 3

1) Lumbar vertebrae

2) Pelvic bones

3) 11th & 12th ribs

Question 4

What are the muscles of the posterior abdominal wall?

Answer 4

1) Medial: Psoas major & minor

2) Laterally: Quadratus lumborum

3) Inferiorly: Iliacus

4) Superiorly: Diaphragm

Question 5

What is the origin of the psoas major muscle?

Answer 5

1) Body of the 12th thoracic vertebrae and all lumbar vertebrae and intervertebral discs and their transverse process

Question 6

Where is Psoas major inserted?

Answer 6

The lesser trochanter of the femur

Question 7

What is the nerve supply of the psoas major muscle?

Answer 7

L2 & L3

Question 8

What are the actions of the psoas major?

Answer 8

Flexion of the thigh at the hip joint

Question 9

What is the origin of Psoas minor?

Answer 9

• not present in some individuals

1) T12

2) L1

Question 10

Where is Psoas minor inserted?

Answer 10

1) Iliopubic eminence

2) Pectineal line

Question 11

What is the nerve supply of the Psoas minor?

Answer 11

Ventral rami of L1

Question 12

What is the action of the Psoas minor?

Answer 12

It weakly flexes the lumbar vertebral column

Question 13

What is the origin of the quadratus lumborum?

Answer 13

1) Transverse process of L5

2) Iliolumbar ligament

3) Iliac crest

Question 14

Where is the quadratus lumborum inserted?

Answer 14

1) Transverse process of L1-L5 vertebrae

2) Inferior border of the 12th rib

Question 15

What is the nerve supply of the quadratus lumborum?

Answer 15

The ventral rami of T12-L4

Question 16

What is the action of the quadratus lumborum muscle?

Answer 16

It depresses and stabilizes the 12th rib and bends the trunk laterally

Question 17

What is the origin of iliacus?

Answer 17

1) 2/3 of the upper lateral part of the iliac fossa

2) Sacro-iliac and iliolumbar ligaments

3) The upper lateral surface of the sacrum

Question 18

Where is the iliacus muscle inserted?

Answer 18

The lesser trochanter

Question 19

What is the nerve supply of the iliacus muscle?

Answer 19

L2 & L3

Question 20

What is the action of the iliacus?

Answer 20

Flexion of the thigh at the hip joint

Question 21

What forms the medial arcuate ligament?

Answer 21

Thickening of the psoas fascia

Question 22

What forms the lateral arcuate ligament?

Answer 22

The thickening of the superior aspect of quadratus lumborum fascia

Question 23

What is the thoracolumbar fascia?

Answer 23

• It is a strong sheet of deep fascia that binds the deep muscles of the back to the sides of the vertebral column
• It encloses the quadratus lumborum anterior and erector spinae muscle posteriorly
• It consists of three layers

Question 24

What are the different layers of the thoracolumbar fascia?

Answer 24

1) ANTERIOR LAYER

2) MEDIAL LAYER

3) POSTERIOR LAYER

Question 25

What does the anterior layer cover and attach to?

Answer 25

1) It covers the anterior surface of the quadratus lumborum 2) Medially it is attached to the lumbar transverse process 3) Laterally it is attached to the aponeurotic origin of the transversus abdominis

Question 26

What is the covering and medial and lateral attachments of the middle layer of the thoracolumbar fascia?

Answer 26

- It covers the back of the quadratus lumborum - Medially it is attached to the lumbar transverse process - Laterally it unites with the anterior layer

Question 27

What are the attachments of the posterior layer of the thoracolumbar fascia?

Answer 27

- It is the strongest layer - Laterally it fuses with the middle layer at the lateral margin of the erector spinae - Medially it is attached to the tups of the lumbar spine

Question 28

Describe the psoas fascia

Answer 28

- It is thick - It extends into the thigh and can form a psoas abscess which extends into the femoral triangle - It is thickened superiorly forming the medial arcuate ligament of the diaphragm

Question 29

What is a psoas muscle abscess?

Answer 29

- Because the psoas muscle and fascia arise from the intervertebral discs some types of infection (like TB and salmonella discitis) affect the discs and other structures spread anteriorly and laterally - In the anterolateral position the infection can spread into the psoas muscle which might appear as a mass below the inguinal ligament

Question 30

What are the branches of the abdominal aorta?

Answer 30

1) Visceral 2) Posterior 3) Terminal branches

Question 31

What are the visceral branches of the abdominal aorta?

Answer 31

- Supply organs/viscera 1) Paired: - Renal - Middle suprarenal - Gonadal 2) Unpaired - Celiac - Superior mesenteric - Inferior mesenteric

Question 32

What are the posterior branches of the abdominal aorta?

Answer 32

- Goes posteriorly to supply the muscles & tissues of the posterior abdominal wall 1) Paired: - Inferior phrenic - Lumbar 2) Unpaired - Median sacral

Question 33

What are the terminal branches of the abdominal aorta?

Answer 33

Common iliac arteries

Question 34

Which organs do the visceral paired branches supply?

Answer 34

1) The middle suprarenal is one of the three sources of blood supply of the suprarenal glands 2) The gonadal artery is found below the middle suprarenal artery and above the inferior mesenteric 3) The renal artery supplies the kidney

Question 35

What is the vertebral level of the renal arteries?

Answer 35

- It arises at the level of the intervertebral disc between L1 and L2 - Right artery is longer than the left one

Question 36

What is the vertebral level of the celiac trunk?

Answer 36

It is one of the unpaired visceral branches of the abdominal aorta found at the superior border of L1

Question 37

What is the vertebral level of the superior mesenteric artery?

Answer 37

The inferior border of L1, behind the pancreatic head and in front of the unicate process

Question 38

What is the vertebral relation of the Inferior mesenteric artery?

Answer 38

Below the head of the pancreas at the L3

Question 39

Inferior phrenic is a branch of which part of the abdominal aorta?

Answer 39

It is from the posterior branches and it is the first branch to come out supplying the diaphragm

Question 40

How many pairs are there of the abdominal aorta's lumbar (a posterior branch)?

Answer 40

- It has 4-pairs - It passes deep to the psoas supplying the: - Vertebral column - Spinal cord - Abdominal wall

Question 41

What is the posterior unpaired branch of the abdominal aorta?

Answer 41

The median sacral artery, which arises just above the bifurcation of the aorta (into the common iliac) posteriorly, it then descends into the pelvis in front of the sacrum

Question 42

At which vertebral level does the IVC begin?

Answer 42

L5 (by the union of the two common iliac veins) - It ascends on the posterior abdominal wall to the right of the midline and enters the thorax at T8

Question 43

Where does the renal vein lie?

Answer 43

Anterior to the renal arteries, the left renal vein is longer than the right

Question 44

What are the tributaries of the "Left" renal veins?

Answer 44

1) Left suprarenal vein 2) Left gonadal vein - Right suprarenal and gonadal vein empties directly into the IVC

Question 45

What are the nerves of the posterior abdominal wall?

Answer 45

1) The lumbar part of the sympathetic trunk 2) Celiac plexus 3) Aortic plexus 4) Hypogastric plexus (one in front of the bifurcation of the aorta called the superior hypogastric plexus, and two on the sides called the inferior hypogastric plexuses) 5) Lumbar plexus of nerves

Question 46

Describe the lumbar part of the sympathetic plexus

Answer 46

- The lumbar trunk consists of 4 pairs of sympathetic ganglia, reaching the abdomen by passing behind the medial arcuate ligament - The right chain descends behind the IVC while the left chain descends behind the abdominal aorta

Question 47

Describe the celiac plexus

Answer 47

- A plexus is a network/convergence of parasympathetic and sympathetic fibers where they interact before traveling to a specific target - The celiac ganglia sends sympathetic branches that surround the upper part of the abdominal aorta, the coeliac trunk ,and coeliac branches, forming the coeliac plexus - Celiac plexus receives parasympathetic innervation from the left gastric nerve (vagus nerve)

Question 48

From where does the celiac plexus receive parasympathetic innervation?

Answer 48

Left gastric nerve (vagus nerve)

Question 49

What are the aortic and hypogastric plexus?

Answer 49

The aortic plexus lies along the front side of the aorta, while the hypogastric plexus (divides into right and left inferior hypogastric plexus around the internal iliac arteries "for the pelvic viscera") lies below the bifurcation of the aorta - The aortic plexus of nerves is continued upwards with the celiac plexus and downwards with the hypogastric plexus

Question 50

How does the sympathetic trunk enter the posterior abdominal wall?

Answer 50

Behind the medial arcuate ligament

Question 51

What forms the lumbar plexus of nerves?

Answer 51

The subcostal nerve and the anterior primary rami of L1-L4, formed by the substance of psoas

Question 52

What are the branches of the lumbar plexus?

Answer 52

- Lateral to psoas: 1) Iliohypogastric and its collateral ilioinguinal (L1) 2) Lateral femoral cutaneous (L2, 3 "posterior division") 3) Femoral (L2, 3, 4 "POSTERIOR DIVISION) - Anterior to psoas: 1) Genitofemoral (L1 + L2) - Medial to psoas: 1) Obturator (L2, 3, 4 "Ant division") 2) Lumbosacral trunk (L4 + L5) (Mnemonic: I To Got Lunch On Friday)