Posterior Abdominal Wall Flashcards
The posterior abdominal wall is mainly composed of:
- 5 Lumbar vertebrae + IV discs
- posterior abdominal wall muscles
- diaphragm
- fascia
- lumbar plexus
- fat, nerves, vessels, lymph nodes
Posterior abdominal muscles include:
- psoas
- quadratus lumborum
- iliacus
- transverse abdominal
- oblique muscles (laterally)
What is a marked central prominence in the posterior wall and creates two paravertebral ‘gutters’ on each side of it?
lumbar vertebral column
The deepest (most posterior) part of the lumbar vertebral ‘gutters’ is occupied by the…?
kidneys + their surrounding fat
What great vessel lies on the anterior aspect of the anteriorly protruding vertebral column?
abdominal aorta
In lean individuals, the lower abdominal aorta lies where?
close to the anterior abdominal wall
Many structures lie anterior to the aorta which may be close to the anterior abdominal wall in thin people. These structures include:
- superior mesenteric artery
- parts of the duodenum
- pancreas
- left renal vein
The posterior abdominal wall is covered with a continuous layer of _____________? It lies between what two structures/layers?
- endoabdominal fascia
parietal peritoneum + the post. ab. muscles
The fascia lining the posterior abdominal wall is continuous with what other fascia?
transversalis fascia
(lines transverse abdominal muscle)
PSOAS FASCIA
covers psoas major m. (psoas sheath)
attached medially = lumbar vertebrae + pelvic brim
superiorly = thickened to form medial arcuate ligament
laterally = fuses with quadratus lumborum + thoracolumbar fascias
Inferior (to iliac crest) = continuous with iliac fascia covering iliacus
THORACOLUMBAR FASCIA
extensive fascial complex
- medially attached to vertebral column
- (lumbar region ) = posterior, middle + anterior layers
(with muscles enclosed between them)
- laterally attached to internal oblique, transverse abdominal, latissimus dorsi
(NOT external obliques)
What part of the thoracolumbar fascia is thin + transparent?
What part is thick + strong?
thin+transparent = thoracic parts of the deep muscles
thick+strong =** lumbar region**
(lumbar = b/t 12th rib + iliac crest)
The anterior layer of the thoracolumbar fascia covers which muscle + is continuous laterally with what structure?
COVERS = quadratus lumborum m.
CONTINUOUS W. = aponeurotic origin of transverse abdominal m.
ANTERIOR THORACOLUMBAR FASCIA =
quadratus lumborum fascia
- thinner, more transparent layer
attachments:
- anterior surfaces of transverse processes of lumbar vertebrae
- iliac crest
- 12th rib
superiorly = thickens to form lateral arcuate ligament
inferiorly = adheres to iliolumbar ligaments
The main paired muscles in the posterior abdominal wall (3):
- Psoas major (inferolaterally)
- Iliacus (lateral to inferior part of psoas major)
- Quadratus lumborum (lateral to superior part of psoas major)
PSOAS MAJOR MUSCLE
(attachment, innervation, action)
Attachment:
superior = transverse processes of lumbar vert.; sides of T12-L5 vert. bodies + discs
Inferior = strong tendon to lessor tronchanter of femur
Innervation:
Lumbar Plexus
(anterior L2-L4 spinal n. branches)
Main action:
- acts inferiorly w. iliacus = flexes thigh (standing); flexes trunk (sitting)
- acts superiorly = flexes vertebral column laterally
- balances trunk
ILIACUS MUSCLE
(attachment, innervation, action)
Attachment:
superior = superior 2/3 of iliac fossa; ala of sacrum; anterior sacroiliac ligaments
Inferior = lesser tronchater of femur + shaft inferior to it; psoas major tendon
Innervation:
Femoral nerve (L2-L4)
Main action:
- flexes thigh
- stabilizes hip joint
- acts w. psoas major
QUADRATUS LUMBORUM MUSCLE
(attachments, innervation, actions)
Attachment:
superior = medial 1/2 interior border of 12th ribs + tip of lumbar transverse processes
Inferior = iliolumbar ligament + internal lip of iliac crest
Innervation:
anterior branches T12 = L1-L4 spinal n.
Main action:
- extends + laterally flexes vertebral column
- fixes 12th rib (inspiration)
The iliopsoas has extensive and clinically important relations to which (8) structures?
When any of these structures is diseased, movement of iliopsoas usually causes pain.
- kidneys
- ureters
- cecum
- appendix
- sigmoid colon
- pancreas
- lumbar lymph nodes
- nerves of post. abdominal wall
When intra-abdominal inflammation is suspected, what test is performed?
iliopsoas test
lie on unaffected side + extend thigh on the affected side against the resistance of the examiner’s hand
- pain with this maneuver is a positive psoas sign
Why is it that disease of the intervertebral + sacroiliac joints may cause spasm of the iliopsoas (protective reflex)?
because. ..
* *psoas lies along the vertebral column** + iliacus crosses the sacroiliac joint
Adenocarcinoma of the pancreas in advanced stages invades the muscles and nerves of the posterior abdominal wall. What symptom does this cause + why?
excruciating pain
- b/c close relationship of the pancreas to the posterior abdominal wall
Psoas Abscess & Turberculosis:
Prevalence of tuberculosis (TB) has been greatly reduced, but still very present in some areas. TB of the vertebral column is quite common. How is this caused by hematogenous spread, and how does it cause a psoas abcess?
- hematogenous spread = infection may spread through blood to the vertebrae
(esp. during childhood)
- TB abscess in lumbar region tends to spread from vertebrae into psoas sheath
= psoas abscess
What occurs as a result of a psoas abscess?
- psoas fascia thickens + forms strong stocking-like tube
- psoas abscess pus passes inferiorly along psoas muscle in fascial tube, over pelvic brim + deep to inguinal ligament
- pus usually surfaces in the superior part of the thigh
*Pus can also reach psoas sheath from posterior mediastinum when thoracic vertebrae are diseased*
Nerves of the Posterior Abdominal Wall:
Components of which nervous systems are associated with the posterior abdominal wall?
** somatic** + autonomic (visceral) nervous systems
Nerves of the Posterior Abdominal Wall:
What path do the subcostal nerves (anterior rami of T12) take to enter the abdomen and reach their target structures?
- arise in the thorax
- pass posterior to lateral arcuate ligaments into abdomen
- run inferolaterally on anterior surface of quadratus lumborum
- pass through the transverse abdominal + internal oblique muscles
- supply the external oblique + skin of the anterolateral abdominal wall
Thoracolumbar out-flow =
Sympathetic nervous system
Craniosaccreal out-flow =
Parasympathetic nervous system
Nerves of the Posterior Abdominal Wall:
What path do the lumbar spinal nerves (L1 - L5) take to enter the abdomin and reach their target structures?
- from spinal cord through intervertebral foramina inferior to corresponding vertebrae
(divide into posterior + anterior rami)
sensory + motor fibers
The initial portions of the **anterior rami of the L1, L2, (occasionally L3) **spinal nerves give rise to what structures?
What type of fibers to these convey to the lumbar sympathetic trunks?
- white communicating branches (L. rami communicantes)
- convey presynaptic sympathetic fibers
- * L4, L5 have no sympathetic supply therefore no lateral horns**
Nerves of the Posterior Abdominal Wall:
The abdominal part of the sympathetic trunks (lumbar sympathetic trunks), consist of 4 ____________ and _______________?
These are continuous with the thoracic part of the trunks deep to what structure?
4 lumbar paravertebral sympathetic ganglia
+
interganglionic branches that connect them
- deep to the medial arcuate ligaments of the diaphragm
Nerves of the Posterior Abdominal Wall:
The lumbar sympathetic trunks descend on what surface of the lumbar vertebrae?
These rest in a groove formed by what adjacent muscle?
anterolateral aspects of the vertebral bodies
- psoas major
Nerves of the Posterior Abdominal Wall:
Inferiorly, the lumbar sympathetic trunks cross what structure before continuing inferiorly into the pelvis as the sacral part of the trunks?
cross the sacral promontory
For the innervation of the abdominal wall + lower limbs, synapses between the presynaptic and postsynaptic fibers occur … (where)?
Postsynaptic sympathetic fibers travel from the lateral aspect of the trunks via _______________ to the anterior rami?
- in the sympathetic trunks
- via gray communicating branches
Which nerve fibers become the thoracoabdominal and subcostal nerves, and the lumbar plexus (somatic nerves)?
What actions do they stimulate in the lowermost trunk and lower limb?
Postsynaptic sympathetic fibers from anterior rami
stimulate:
**- vasomotion **(stimulates blood vessels)
**- **sudomotion **(stimulates sweat glands)
- pilomotion (stimulates erector pili)
What type of nerve fibers are conveyed by the lumbar splanchnic nerves arising from the medial aspect of the lumbar sympathetic trunks?
What do these nerves innervate?
- presynaptic sympathetic fibers
- innervate** pelvic viscera**
Partial Lumbar Sympathectomy
surgical removal of two or more lumbar sympathetic ganglia by division of their rami communicantes
- treatment for some patients with arterial disease in the lower limbs
- surgical access to the sympathetic trunks is commonly through a lateral extraperitoneal approach b/c the sympathetic trunks lie retroperitoneally in the extraperitoneal fatty tissue
Partial Lumbar Sympathectomy:
The surgeon splits the muscles of the anterior abdominal wall and moves the peritoneum medially + anteriorly to expose the medial edge of the psoas major (along which the sympathetic trunk lies).
The left trunk is overlapped slightly by the …?
The right trunk is covered by the …?
left = aorta
right = inferior vena cava
Partial Lumbar Sympathectomy:
Knowing that identification of the sympathetic trunks is not easy, surgeons take great care not to remove inadvertently part of these (3) structures…?
genitofemoral nerve
lumbar lymphatics
ureter
lumbar plexus
anterior rami of L1 through L4 nerves
- anterior to lumbar transverse processes, within proximal attachment of the psoas major
branches of lumbar plexus:
- femoral nerve (L2 - L4)*
- obturator nerve (L2 - L4)*
- lumbosacral trunk (L4, L5)*
- ilioinguinal + iliohypogastric nerves (L1)
- genitofemoral nerve (L1, L2)
- lateral femoral cutaneous nerve (L2, L3)
- accessory obturator nerve (L3, L4)
femoral nerve
(L2 - L4)
- emerges from lateral border of psoas major
- innervates the iliacus + passes deep to inguinal ligament/iliopubic tract to the anterior thigh
- supplies the flexors of the hip + extensors of the knee
obturator nerve
(L2 - L4)
- emerges from medial border of the psoas major
- passes into lesser pelvis, passing inferior to the superior pubic ramus (through the obturator foramen) to the medial thigh
- supplies the adductor muscles
lumbosacral trunk
(L4, L5)
- passes over the ala (wing) of sacrum + descends into the pelvis to participate in the formation of the sacral plexus with the anterior rami of S1 - S4 nerves
ilioinguinal + iliohypogastric nerves
(L1) - anterior ramus
- enter abdomen posterior to medial arcuate ligament
- passes inferolaterally, anterior to the quadratus lumborum
- superior + parallel to iliac crest, piercing the transverse abdominal near the anterior superior iliac spine (ASIS)
- pass through the internal + external obliques to supply the abdominal muscles + skin of the inguinal and pubic regions
genitofemoral nerve
(L1, L2)
- pierces psoas major + runs inferiorly on its anterior surface, deep to the psoas fascia
- divides lateral to common + external iliac arteries into femoral and genital branches
lateral femoral cutaneous nerve
(lateral cutaneous nerve of the thigh)
(L2, L3)
- runs inferolaterally on iliacus + enters the thigh deep to the inguinal ligament/iliopubic tract, just medial to the anterior superior iliac spine
- supplies skin on anterolateral surface of the thigh
accessory obturator nerve
(L3, L4)
- present almost 10% of the time
- parallels the medial border of the psoas, anterior to the obturator nerve - crosses superior to superior pubic ramus in close proximity to the femoral vein
The major neurovascular bundle of the inferior trunk includes what structures?
(It courses in the midline of the posterior abdominal wall, anterior to the bodies of the lumbar vertebrae)
- abdominal aorta
- inferior vena cava
- aortic periarterial nerve plexus
Abdominal Aorta
- gives rise to most arteries supplying the posterior abdominal wall
- approximately 13 cm in length
- starts = aortic hiatus in the diaphragm (T12 vertebra level or 2.5 cm superior to transpyloric plane)
ends = L4 vertebra level; bifutcates into right + left common iliac arteries
- aortic bifurcation = 2 - 3 cm inferior + left of umbilicus
(@ level of iliac crests)
common iliac arteries
(right + left)
- diverge + run inferolaterally
(follow medial border of the psoas muscles to pelvic brim)
- each common iliac artery divides into internal + external iliac arteries
external iliac artery
(branch of left/right common iliac arteries)
- follows the iliopsoas muscle
- before leaving abdomen, gives rise to inferior epigastric and deep circumflex iliac arteries (supply the anterolateral abdominal wall)
What unpaired parietal branch may be said to occupy a fourth (posterior) plane because it arises from the posterior aspect of the aorta just proximal to its bifurcation?
median sacral artery
The median sacral artery could be considered a midline ________________?
continuation of the aorta
(in which case its lateral branches, small lumbar arteries, and lateral sacral branches, would be included as part of the paired parietal branches)
Deep palpation of the midabdomen can detect an aortic aneurysm, which usually results from …?
a congenital or acquired weakness of the arterial wall
How ca you apply pressure to control bleeding in the pelvis or lower limbs (esp. in children and lean persons)?
(anterior abdominal wall is relaxed)
- firm pressure on the anterior abdominal wall, over the umbilicus
- inferior part of the abdominal aorta may be compressed against the body of the L4 vertebra
What line is helpful to identify the site of aortic bifurcation when examining obese persons in whom the umbilicus is not a reliable surface landmark?
line joining the highest points of the iliac crests
(just to the left of the midpoint)
The veins of the posterior abdominal wall are tributaries of the______________, except for the left testicular or ovarian vein, which enters the _________instead.
- inferior vena cava (IVC)
- left renal vein
Where does the IVC begin, ascend, and exit the abdominal cavity?
begins = anterior to L5 vertebra @ union of common iliac veins
(inferior to the bifurcation of the aorta and posterior to the proximal part of the right common iliac artery)
ascends = right sides of L3 - L5 vertebrae bodies + on right psoas major to right of the aorta
exits = thru caval opening in diaphragm; enters thorax at T8 vertebral level
The tributaries of the IVC correspond to the ______________ branches of the abdominal aorta?
The tributaries of the portal vein correspond to the ___________ branches of the aorta?
IVC = paired visceral + parietal
portal vein = unpaired visceral
The branches of the IVC corresponding to the paired viscera branches of the abdominal aorta include … (4)?
- right suprarenal vein
- right + left renal veins
- right gonadal (testicular or ovarian) vein
Paired parietal branches of the IVC include … (4)?
inferior phrenic veins
3rd (L3) + 4th (L4) lumbar veins
common iliac veins (union of external + internal iliac veins)
What are the 3 collateral routes available for venous blood to return to the heart when the IVC is obstructed or ligated?
- superior + inferior epigastric veins
- thoracoepigastric vein
- epidural venous plexus* (inside vertebral column)
* *communicates with lumbar veins + tributaries of azygos system*
In the posterior abdomen, where do lymphatic vessels + lymph nodes lie?
along the aorta
along IVC
along iliac vessels
Where do the common iliac nodes receive lymph from + where do they drain lymph to?
receive from = external + internal iliac lymph nodes
drain to = right + left lumbar lymph nodes
Efferent vessels from which lymph nodes form the intestinal lymphatic trunks + participate in the confluence of lymphatic trunks that gives rise to the thoracic duct?
What structures do these lymph nodes receive lymph from?
celiac, superior + inferior mesenteric nodes
receive lymph from:
- alimentary tract
- liver
- spleen
- pancreas
The thoracic duct begins with the convergence of what ducts?
Where is this located?
These form what dialation/structure?
- main lymphatic ducts of the abdomen
- anterior to L1 + L2 vertebrae bodies; between right crus of diaphragm + aorta
convergence = the chyle cistern
Where does the thoracic duct end?
ends by entering the venous system at:
junction of the left subclavian + internal jugular veins
(the left venous angle)
