Posterior Abdominal Wall (Brauer)

Question 1

What are the muscles of the posterior abdominal wall?

Answer 1

• psoas major and minor
• iliacus
• quadratus lumborum
• diaphragm

Question 2

Psoas major and minor

• origin:
• insertion:
• innervation:

Answer 2

Psoas major and minor

• origin: transverse processes and sides of vertebral bodies and intervertebral discs of T12-L5
• insertion: tendon to the lesser trochanter of femur (major)
• innervation: anterior rami of L1-3

Question 3

Iliacus

• origin:
• insertion:
• innervation:

Answer 3

Iliacus

• origin: superior 2/3’s iliac fossa, ala, anterior sacro-iliac ligaments
• insertion: lesser trochanter and shaft below
• innervation: femoral nerve (L2-4)

Question 4

Quadratus lumborum

• origin:
• insertion:
• innervation:

Answer 4

Quadratus lumborum

• origin: iliolumbar ligament and lip of iliac crest
• insertion: medial half of inferior surface of 12th rib and tips of lumbar transverse processes
• innervation: T12, L1-4

Question 5

• etiology: diseases of organs (e.g. TB spread into abd), cancers (e.g. adenocarcinomas), infections deep to psoas fascia
• presentation: back/flank pain, fever, limp inguinal mass; lower abd pain exacerbated by extending thigh (“psoas sign”)

Answer 5

psoas abscess

Question 6

• fascial thickening of the psoas fascia
• spans lumbar body and tip of L1 transverse process
• lateral to median arcuate ligament

Answer 6

medial arcuate ligament

Question 7

• fasical thickening of quadratus lumborum M.
• runs from L1 transverse process to tip of 12th rib

Answer 7

lateral arcuate ligament

Question 8

• tendinous arch of the crura of the diaphragm
• unites right and left crura

Answer 8

median arcuate ligament

Question 9

What are the unpaired arteries of the posterior abdominal wall?

Answer 9

• celiac trunk (T12)
• superior mesenteric artery (L1)
• inferior mesenteric artery (L3)
• median sacral artery

Question 10

What are the paired arteries of the posterior abdominal wall?

Answer 10

• subcostal arteries (not shown)
• inferior phrenic arteries
• suprarenal arteries
• renal arteries (L2)
• gonadal arteries (L2)
• lumbar arteries
• deep circumflex iliac arteries

Question 11

What are the main veins of the posterior abdominal wall?

Answer 11

• inferior vena cava: beings anterior to L5 and right of medial plane, passes through caval hiatus of diaphragm
• tributaries of IVC: corresponding veins of paired visceral and parietal branches of aorta: paired visceral include suprarenal v., renal v., and gonadal v.; paired parietal branches include inferior phrenic v., 3rd and 4th lumbar vs., and common iliac v.
• ascending lumbar v. and azygos v. connect the SVC and IVC, either directly or indirectly
• venous return from abdominal viscera returns via portal venous system/hepatic vein

Question 12

What are the 3 diaphragm openings?

Answer 12

• caval opening (T8 level): IVC, right phrenic nerve
• esophageal hiatus (T10 level): esophagus, anterior/posterior vagal trunks
• aortic hiatus (T12 level): aorta, thoracic duct, sometimes azygos and hemiazygos veins

Question 13

What are the attachment points and associated tendons of the muscular diaphragm?

Answer 13

muscular portion:

• sternal part: attaches to xiphoid (may/may not be present)
• costal part: attaches to inferior 6 costal cartilages
• lumbar (crural part): attaches to lumbar vertebral bodies

central tendon

crura:

• right crus: larger and longer (L1-L3/4 vertebral bodies), some fibers run along left side of aortic hiatus
• left crus (L1-3 vertebral bodies)

Question 14

What are the arteries of the diaphragm?

Answer 14

• superior side: musculophrenic and pericardiophrenic as. (off internal thoracic a.); and superior phrenic a. (off thoracic aorta)
• inferior side (shown in pic): inferior phrenic a. (off abd aorta); and intercostal branches for peripheral diaphragm

Question 15

What are the 2 different types of hiatal hernias and what is thought to cause them?

Answer 15

• para-esophageal hiatal hernia: pouch of peritoneum and stomach fundus extends through esophageal hiatus usually anterior to esophagus; gastric regurgitation usually does not occur as cardiac portion is normal
• sliding hiatal hernia: abdominal esophagus, cardiac, and portion of fundus extends through esophageal hiatus; regurgitation of stomach contents is possible
• both are thought to be due to weakening of muscular diaphragm

Question 16

Where are the kidneys located in terms of anterior aspect?

Answer 16

• retroperitoneal lying about T12-L3
• right kidney sits lower
• suprarenal glands lie above
• kidney size: ~10 cm long, 5 cm wide, 2 cm thick
• renal hilum: entrance to renal sinus (area in kidney where BV, renal pelvis, and nerves are located)

Question 17

Where are the kidneys located in terms of posterior aspect?

Answer 17

• posteriorly, superior parts lie deep to 11th and 12th ribs
• left kidney hilum near transpyloric plane (~5 cm from median plane)
• transpyloric plane runs through superior pole of right kidney (~2.5 cm lower than left)
• inferior pole of right kidney is approximately index fingers breath superior to iliac crest

Question 18

What structures are important to remember when taking a posterior kidney approach?

Answer 18

• right kidney lower than left
• quadratus lumborum muscle lies posterior to largest part of kidney (w/ intervening fat)
• nerves: subcostal (protected by 12th rib), iliohypogastric (L1), ilioinguinal (L1)

Question 19

What are the different types of renal fat and associated structures?

Answer 19

• perinephric fat: adjacent kieny capsule, extends into renal pelvis
• renal fascia: covers fat enveloping kidney and suprarenal gland; blends and ensheaths renal vessels; superiorly c/w inferior diaphragmatic fascia
• paranephric fat: external to renal fascia
• normal renal mobility is ~3cm

Question 20

What are the different intrarenal structures?

Answer 20

• hilum
• sinus (typically filled w/ fat)
• pelvis
• calices
• cortex
• medulla
• pyramids
• columns
• papilla
• segmental a./v.

Question 21

What is the location and constrictions of the ureters?

Answer 21

• location: run inferiorly from renal pelvis passing over pelvic brim and along lateral pelvic wall, running posterior to ducuts deferens (male) and uterine artery (female)
• constrictions (potential sites of obstructions): (1) junction of ureter w/ renal pelvis, (2) crossing pelvic brim, and (3) entering bladder wall
• pyelogram: x-ray of ureter enhanced w/ contrast media

Question 22

What is the arterial supply to the kidneys and ureters?

Answer 22

renal arteries: segmental arteries

ureter:

• renal branches
• gonadal branches
• abdominal aorta branches
• iliac branches
• superior vesical branches
• pelvic branches: rectal, uterine, vaginal, inferior vesicular

Question 23

What is the location, blood supply, and innervation of the suprarenal (adrenal) glands?

Answer 23

• right suprarenal gland: lies near right crus, right kidney, and IVC
• left suprarenal gland: lies near left crus, spleen, stomach, and pancreas
• blood supply: superior, middle, and inferior suprarenal arteries; corresponding veins
• innervation: preganglionic sympathetic from T10-L1; celiac plexus and abdominopelvic splanchnic nerves

Question 24

What is the lymphatic drainage of the posterior abdominal wall?

Answer 24

• common iliac lymph nodes: from external/internal iliac nodes, drain into lumbar lymph nodes
• lumbar lymph nodes: run along both sides of IVC and aorta, receive from posterior abd/pelvic walls and organs, form lumbar lymphatic trunks
• pre-aortic lymph nodes: form intestinal lymphatic trunks draining from alimentary tract, liver, spleen, and pancreas
• all collected into cisterni chyli (beginning of thoracic duct)

Question 25

What is the innervation to the posterior abdominal wall?

Answer 25

- subcostal n. (T12) - iliohypogastric n. (L1) - ilioinguinal n. (L1) - genitofemoral n. (L1, L2) - lateral femoral cutaneous n. (L2, L3) - femoral n. (L2-4) - obturator n. (L2-4) - lumbosacral trunk (L4, L5)

Question 26

Root of lumbar plexus - branch: iliohypogastric - origin: - spinal segements: - function motor: - function sensory:

Answer 26

Root of lumbar plexus - branch: **iliohypogastric** - origin: anterior ramus L1 - spinal segements: L1 - function motor: internal oblique and transversus abdominis - function sensory: posterolateral gluteal skin and skin in pubic region

Question 27

Root of lumbar plexus - branch: ilioinguinal - origin: - spinal segements: - function motor: - function sensory:

Answer 27

Root of lumbar plexus - branch: **ilioinguinal** - origin: anterior ramus L1 - spinal segements: L1 - function motor: internal oblique and transversus abdominis - function sensory: skin in upper medial thigh, either skin over root of penis and anterior scrotum or mons pubis and labium majus

Question 28

Root of lumbar plexus - branch: genitofemoral - origin: - spinal segements: - function motor: - function sensory:

Answer 28

Root of lumbar plexus - branch: **genitofemoral** - origin: anterior rami L1-2 - spinal segements: L1-2 - function motor: genital branch - male cremasteric muscle - function sensory: genital branch - skin of anterior scrotum or skin of mons pubis and labium majus; femoral branch - skin of upper anterior thigh

Question 29

Root of lumbar plexus - branch: lateral cutaneous nerve of thigh - origin: - spinal segements: - function motor: - function sensory:

Answer 29

Root of lumbar plexus - branch: **lateral cutaneous nerve of thigh** - origin: anterior rami L2-3 - spinal segements: L2-3 - function motor: - function sensory: skin on anterior and lateral thigh of knee

Question 30

Root of lumbar plexus - branch: obturator - origin: - spinal segements: - function motor: - function sensory:

Answer 30

Root of lumbar plexus - branch: **obturator** - origin: anterior rami L2-4 - spinal segements: L2-4 - function motor: obturator externus, pectineus, and muscles in medial compartment of thigh - function sensory: skin on medial aspect of thigh

Question 31

Root of lumbar plexus - branch: femoral - origin: - spinal segements: - function motor: - function sensory:

Answer 31

Root of lumbar plexus - branch: **femoral** - origin: anterior rami L2-4 - spinal segements: L2-4 - function motor: iliacus, pectineus, and muscles in anterior compartment of thigh - function sensory: skin on anterior thigh and medial surface of leg