Posterior Abdominal Wall Flashcards
What are the muscles of the posterior abdominal wall
psoas major
psoas minor
iliacus
quadratus lumborum
Where is the iliacus located?
Large triangular muscle located lateral to the inferior part of psoas major
What is the origin of the iliacus?
Ala of sacrum, iliac fossa and anterior sacroiliac l.
What is the insertion of the iliacus?
Lesser trochanter of femur with psoas major m.
What is the innervation of the iliacus?
Femoral n. (L2-4)
What is the action of the iliacus?
Flexes thigh and stabilizes hip joint
What and where is the quadratus lumborum located?
Quadrilateral shaped muscle forming a sheet on posterior abdominal wall
What crosses superiorly over the quadratus lumborum?
Lateral arcuate ligament
What nerves cross the quadratus lumborum?
Subcostal n. and branches of lumbar plexus cross this m.
What is the origin of the quadratus lumborum?
12th rib and lumbar TPs
What is the insertion of the quadratus lumborum?
Iliolumbar l. and iliac crest
What is the innervation of the quadratus lumborum?
VPR of T12-L4
What is the action of the quadratus lumborum?
Depresses/stabilizes 12th rib for respiratory muscles (thoracic diaphragm
contracts against it during inspiration); laterally flexes vertebral column
What lines the posterior abdominal wall?
Lined internally by parietal peritoneum
Where is endoabdominal fascia found?
Between parietal peritoneum and musculature
What is the endoabdominal fascia continuous with?
Continuous anteriorly with transversalis fascia on anterolateral abdominal wall
What and where is the thoracolumbar fascia found?
Thin and transparent in thoracic region
Thick and strong in lumbar region
- Attached to vertebrae and spans between 12th rib and iliac crest
How is the thoracolumbar fascia found in regards to the deep back mm.?
Anterior, middle and posterior layers split to enclose deep back mm
Between which layers of the thoracolumbar fascia are the quadratus lumborum located and what muscles attach laterally?
Quadratus lumborum m. located between anterior and middle layers
- Internal abdominal oblique and transversus abdominis mm. attach laterally
Between which layers of the thoracolumbar fascia are the erector spinae mm. located and what muscles attach posteriorly?
located between middle and posterior layers
- Comparable to rectus sheath, but stronger due to vertebrae
- Latissimus dorsi m. attaches to lateral aspect of posterior layer
What are fascial abscesses?
Vertebral disease or infection may spread though psoas sheath
- Fascial compartment surrounding psoas major m.
What do fascial abcesses do to the fascia?
Psoas abscess causes this fascia to thicken and become very taut
Where does pus from fascial abcesses travel and via what?
Pus will spread through this compartment to the superior thigh
-Via lacuna musculorum
What will pus from fascial abcesses do to the muscle?
Pus accumulation will compress this muscle and cause pain
What are the somatic nerves of the posterior abdominal wall?
subcostal lumbar spinal lumbar plexus of nerves - iliohypogastric - ilioinguinal - lateral femoral cutaneous - femoral - genitofemoral - obturator - lumbosacral trunk
What is the nerve root of subcostal n?
VPR of T12
where is the subcostal nerve found?
- Located just inferior to 12th rib
- Laterally located between transversus abdominis and internal oblique mm.
- Passes posterior to lateral arcuate l. and crosses quadratus lumborum m.
What does the subcostal nerve innervate?
Innervates anterolateral abdominal wall mm. and T12 dermatome
What do the dorsal rami of lumbar spinal nerves supply?
Dorsal rami supply mm. and skin of back
What do the ventral rami of lumbar spinal nerves pass through and form?
Ventral rami pass into psoas major m. and form lumbar plexus of nerves
What nerve roots make up the lumbar plexus of nerves?
Consists of VPR from L1-L4
What nervous autonomics do the lumbar plexus of nerves receive and via what?
Each receives postsynaptic sympathetics via gray rami communicantes
Is the quadratus lumborum retroperitoneal or intraperitoneal?
Retroperitoneal
What does the VPR of L1 split into?
Iliohypogastric and ilioinguinal nn
Where does the VPR of L1 split?
May split proximally in psoas major m., midway through pass on posterior abdominal wall or distally near ASIS
Where do the Iliohypogastric and ilioinguinal nn pass?
- Pass posterior to medial arcuate l. and cross quadratus lumborum m.
- Parallel iliac crest and pierce transversus abdominis m. near ASIS
What do the Iliohypogastric and ilioinguinal nn innervate?
Innervate abdominal oblique and transversus abdominis mm. and L1 dermatome anteriorly
What nerve roots make up the lateral femoral cutaneous nerve?
VPR of L2-3
Where does the lateral femoral cutaneous nerve pass?
- Pass inferolaterally across ilacus m.
- Enters thigh deep to inguinal l. and medial to ASIS
What does the lateral femoral cutaneous n. innervate?
Sensory to anterolateral skin of thigh
What nerve roots make up the femoral nerve?
VPR of posterior divisions of L2-4
Where does the femoral nerve pass?
- Emerges from the lateral border of psoas major m (iliacus innervation)
- Passes deep to inguinal l. and then to anterior thigh (hip flexor and knee extensor innervation)
What does the femoral n. innervate?
Innervates iliacus m. and hip flexors and knee extensors
What nerve roots make up the genitofemoral nerve?
VPR of L1-L2
Where does the genitofemoral nerve pass?
Sits on anterior surface of psoas major m.
What does the genital branch of the genitofemoral nerve supply?
- Sensory to anterolateral skin of scrotum/labia majora
- Motor to cremaster m.
Where does the genital branch of the genitofemoral nerve pass?
Genital branch passes through deep inguinal ring
Where does the femoral branch of the genitofemoral nerve pass?
Femoral branch passes along external iliac a.
What does the femoral branch of the genitofemoral nerve supply?
Sensory innervation over femoral triangle
What nerve roots make up the obturator nerve?
VPR of L2-4
Where does the obturator nerve pass?
- Runs along medial border of psoas major m. (lateral to iliac vessels)
- Passes through obturator canal
What does the obturator nerve supply?
Innervates medial thigh mm.
What nerve roots make up the lumbosacral trunk?
VPR L4-5
Where does the lumbosacral trunk pass?
Medial to psoas major m. where it passes over ala of sacrum
What does the lumbosacral trunk supply?
Participates with S1-4 in forming sacral plexus
What supplies sympathetic innervation in the posterior abdominal wall?
Lumbar sympathetic trunk
Abdominopelvic splanchnic nn
Lumbar splanchnic nn
What is the lumbar sympathetic trunk?
4 paravertebral ganglia and associated interganglionic segments
Is the lumbar sympathetic trunk continuous with the thoracic and sacral sympathetic trunk?
Yes
Where is the lumbar sympathetic trunk located?
Located anterolaterally to lumbar vertebral bodies
Between what levels do the presynaptic sympathics originate?
Presynaptic sympathetics originate from lateral horn of T1 to as low as L2
How do presynaptic sympathetics enter the sympathetic trunk?
Enter trunk via white rami communicantes
How do postsynaptic sympathetics exit the lumbar ventral rami?
via gray rami
Where do the presynaptic sympathetics of the abdominopelvic splanchnic nerves originate from?
Presynaptic sympathetics originate from lateral horn between T5-L2
How do presynaptic sympathetics enter the adominopelvic splanchnic nerves?
Enter sympathetic trunk via white rami communicantes
Where do postsynaptic sympathetics of adominopelvic splanchnic nerves travel?
Postsynaptic Sympathetics pass through sympathetic trunk without synapsing
At what levels does the greater splanchnic nerve arise from?
T5-9
At what levels does the lesser splanchnic nerve arise from?
T10-11
At what levels does the least splanchnic nerve arise from?
T12
Where do the thoracic splanchnic synapse?
Synapse in either celiac, superior mesenteric or aorticorenal ganglia
Where do the lumbar splanchnic nerves arise from?
Arise from L1-2 or 3
Where do the lumbar splanchnic synapse?
Synapse in inferior mesenteric ganglion
Where do postsynaptic sympathetics exit from the chain?
Exit from the respective prevertebral ganglia
How do the sympathetics of the posterior abdominal wall enter the abdominal viscera?
Following the periarterial plexuses
What do the sympathetics of the posterior abdominal wall do?
Vasoconstriction in abdominal viscera
- Inhibits GI activity
What do visceral afferents of the posterior abdominal wall travel with?
Accompany sympathetics retrograde through splanchnic nn.
What do visceral afferents and their accompaniment of sympathetics do in regards to pain?
Referred pain is to dermatomes associated with segmental levels where presynaptic sympathetics originate
What provide parasympathetic innervation to the posterior abdominal wall?
Anterior/posterior vagal trunks
Pelvic splanchnic nn.
Where are the anterior/posterior vagal trunks found in the posterior abdominal wall?
Emerge from esophageal plexus and pass through esophageal hiatus
What autonomic innervation do the Anterior/posterior vagal trunks carry?
Contain presynaptic parasympathetics
What plexuses do the Anterior/posterior vagal trunks contribute to?
Contribute to same plexuses as splanchnic nn.
What do the Anterior/posterior vagal trunks innervate?
Innervate lower esophagus to splenic flexure of colon and most viscera
- Carry visceral afferents for reflex superior to middle of sigmoid colon
Do the pelvic splachnic nerves associate with sympathetic innervation?
no, Have nothing to do with sympathetic innervation
- Do not attach to sympathetic trunk
What nerve roots make up the pelvic splanchnic nerves?
VPR of S2-4
Where do the pelvic splanchnic nerves convey presynaptic parasympathetics to?
Presynaptic parasympathetics to hypogastric plexuses
What do the pelvic splanchnic nerves innervate?
Innervate from splenic flexure of colon to rectum and pelvic viscera
- Carry visceral afferents for reflex and pain inferior to middle of sigmoid colon
Where do presynaptic parasympathetics of the posterior abdominal wall synapse and what do they do?
Presynaptics synapse on postsynaptic cells in intrinsic ganglia
- Stimulates GI activity
List the autonomic plexuses of the posterior abdominal wall
Celiac plexus Superior mesenteric plexus Inferior mesenteric plexus Superior hypogastric plexus Inferior hypogastric plexus
What autonomic innervations do the autonomic plexuses of the posterior abdominal wall contain?
Contain both sympathetic and parasympathetic neurons
Where are the autonomic plexuses of the posterior abdominal wall found?
Surround abdominal aorta and/or its major arterial branches
Where is the parasympathetic intrinsic ganglia found?
In wall of gut or viscera (i.e. Auerbach’s myenteric plexus)
What autonomics contribute to the celiac plexus?
- Sympathetic contribution via greater and lesser splanchnic nn.
- Parasympathetic contribution via posterior vagal trunk
Where does the celiac plexus supply?
Primarily to foregut derivatives
What autonomics contribute to the superior mesenteric plexus?
1) Sympathetic contribution via lesser and least splanchnic nn.
2) Parasympathetic contribution via posterior vagal trunk
Where does the superior mesenteric plexus supply?
Primarily to midgut derivatives
What autonomics contribute to the Inferior mesenteric plexus?
1) Sympathetic contribution from lumbar splanchnic nn
2) Parasympathetic contribution via pelvic splanchnic nn.
Where does the inferior mesenteric plexus supply?
Primarily to hindgut derivatives
What autonomics contribute to the Superior hypogastric plexus?
Sympathetic contribution from lumbar splanchnic nn.
Where is the Superior hypogastric plexus located?
Anterior to bifurcation of abdominal aorta
Where does the Superior hypogastric plexus supply?
Innervates ureteric and gonadal plexuses
What autonomics contribute to the inferior hypogastric plexus?
1) Sympathetic contribution via lumbar splanchnic nn. (and to a small extent sacral splanchnic nn.)
2) Parasympathetic contribution via pelvic splanchnic nn.
Where is the inferior hypogastric plexus located?
Connected to superior hypogastric plexus via hypogastric nn
What does the inferior hypogastric plexus supply?
Supplies pelvic viscera
Between what levels is the abdominal aorta found?
Anterior to T12-L4 vertebrae
What are the unpaired anterior visceral branches of the abdominal aorta?
o Celiac trunk (T12)
o Superior mesenteric a. (L1)
o Inferior mesenteric a. (L3)
What are the paired lateral visceral branches of the abdominal aorta?
o Middle suprarenal a. (L1)
o Renal a. (L1)
o Gonadal a. (testicular or ovarian aa.) (L2)
List the lumbar plexus of nerves in order from lateral (and superior) to medial
Iliohypogastric Ilioinguinal lateral femoral cutaneous femoral genitofemoral obturator lumbosacral trunk
What are the paired parietal branches of the abdominal aorta?
o Subcostal a. (T12)
o Inferior phrenic a. (T12)
o Lumbar aa. (L1-4)
Where does the abdominal aorta bifurcate and into what?
At L4 it bifurcates into common iliac aa.
Where does the median sacral artery originate from?
Median sacral a. originates at bifurcation of abdominal aorta
Where does the common iliac arteries travel?
Follow medial border of psoas major m. to pelvic brim
