Posterior Abdominal Wall

Question 1

Which muscles are located in the posterior abdominal wall?

Answer 1

Psoas major and minor, iliacus and quadratus lumborum

Question 2

What is the origin and insertion for psoas major and minor?

Answer 2

Origin: TPs and sides of vertebral bodies + intervertebral discs (T12-L5)
Insertion: tendon to the lesser trochanter of femur (major)

Question 3

What innervates the psoas major and minor?

Answer 3

Anterior rami of L1-3

Question 4

What is the origin and insertion for the iliacus muscle?

Answer 4

Origin: superior 2/3s iliac fossa, ala and anterior sacroiliac ligaments
Insertion: lesser trochanter and shaft below

Question 5

What innervates the iliacus?

Answer 5

Femoral nerve (L2-4)

Question 6

What is the origin and insertion for the quadratus lumborum?

Answer 6

Origin: iliolumbar ligament and lip of iliac crest
Insertion: medial half of inferior surface of 12th rib + tips of lumbar transverse processes

Question 7

What innervates the quadratus lumborum?

Answer 7

T12, L1-4

Question 8

What sx are associated with a psoas abscess?

Answer 8

Back or flank pain, fever, limp, inguinal mass

Lower abdominal pain exacerbated by extending thigh (psoas sign)

Question 9

What are some causes for a psoas abscess?

Answer 9

Disease of organs (e.g. TB spread into abdomen)
Cancers (e.g. adenocarcinomas)
Infections deep to psoas fascia

Question 10

What is the medial arcuate ligament?

Answer 10

Fascial thickening of the psoas fascia
Spanning lumbar body and top of L1 TP
Lateral to the median arcuate ligament

Question 11

What is the lateral arcuate ligament?

Answer 11

Fascial thickening of quadratus lumborum muscle running from L1 to TP to the tip of the 12th rib

Question 12

What is the median arcuate ligament?

Answer 12

Tendinous arch of the crura of the diaphragm

Unites right and left crura

Question 13

What are the unpaired arteries of the posterior abdominal wall?

Answer 13

Celiac trunk (T12), SMA (L1), IMA (L3) and median sacral artery

Question 14

What are the paired arteries of the posterior abdominal wall?

Answer 14

Subcostal arteries, inferior phrenic, suprarenal, renal, gonadal, lumbar and deep circumflex iliac arteries

Question 15

Describe the IVC

Answer 15

Begins anterior to L5 and right of medial plane

Passes through caval hiatus of diaphragm

Question 16

What are the tributaries of the IVC?

Answer 16

Corresponding veins of paired visceral and parietal branches of aorta
Paired visceral branches include suprarenal, renal and gonadal veins
Paired parietal branches include inferior phrenic, 3rd and 4th lumbar and common iliac veins

Question 17

The ascending lumbar V and azygos V connect which veins?

Answer 17

Superior and inferior vena cava - either directly or indirectly

Question 18

The right gonadal vein empties directly into which vein?

Answer 18

The IVC whereas the left empties into the left renal vein which then drains into IVC

Question 19

Venous return from abdominal viscera returns via what?

Answer 19

Portal venous system/hepatic vein

Question 20

Describe the common iliac LNs

Answer 20

From external/internal iliac nodes

Drain into lumbar LNs

Question 21

Describe lumbar LNs

Answer 21

Run along both sides of IVC and aorta
Receive from posterior wall and posterior pelvic wall organs
From lumbar lymphatic trunks

Question 22

Describe pre-aortic LNs

Answer 22

Forming intestinal lymphatic trunks draining from alimentary tract, liver, spleen and pancreas

Question 23

All posterior wall lymphatics are collected into what?

Answer 23

Cisterni chyli (beginning of thoracic duct)

Question 24

Describe the lumbar plexus

Answer 24

Composed of anterior rami of lumbar spinal nerves
Can be revealed by removing the psoas muscle
Nerves include Iliohypogastric, ilioinguinal, genitofemoral, lateral cutaneous nerve of the thigh, obturator, femoral nerve, lumbosacral trunk