Posterior Abdominal Wall
Vasculature
arteries consist of the paired branches of the abdominal aorta
- inferior phrenics
: arise from posterolateral aorta just below the diaphragm; supply diaphragm
- suprarenal arteries
: arise from lateral aorta; supply suprarenal glands
- superior: inferior phrenics
- middle: suprarenals
- inferior: renal artery branches
- renal arteries
: arise at L1/L2; branch into superior; anterior superior; anterior inferior; posterior; inferior segmental arteries
- gonadal arteries
: testicular, ovarian; run along psoas major; testicular enters inguinal canal; ovarian enters the pelvis minor
- lumbar arteries
: four arteries; analagous to intercostal arteries of thorax
veins run alongside the arteries into the IVC with two exceptions:
- left suprarenal vein
and left gonadal vein dump into the left renal vein not directly into the IVC
- renal veins are anterior to renal arteries
lymphatics
superior to the umbilicus: drainage to the axillary lymph nodes
inferior to the umbilicus: drainage to the inguinal nodes Þ preaortic nodes Þ cisterna chyli Þ thoracic duct
Nerves
Autonomic
sympathetic trunk enters abdomen posterior to the medial arcuate ligament
- usually composed of five lumbar sympathetic ganglia
celiac plexus: on either side of the celiac trunk (solar plexus)
greater splanchnic nerve: arises from ganglia at T5 – T9
lesser splanchnic nerve: arises from ganglia at T10 – T11
least splanchnic nerve: arises from ganglia at T12
kidneys are innervated by lesser and least splanchnics (T10 - L1)
suprarenal glands are innervated by greater, lesser, least splanchnic, lumbar nerves (T6 - L2)
foregut: greater splanchnic nerve
midgut: lesser and least splanchic nerve
hindgut: lumbar nerves
Somatic
subcostal nerve (12th thoracic nerve): supplies anterior abdominal wall between the umbilicus and pubic symphysis
iliohypogastric nerve: supplies skin of suprapubic and inguinal regions
ilioinguinal nerve: supplies skin of the inner thigh and scrotum
- iliohypogastric and ilioinguinal nerves arise from a common branch of L1
genitofemoral nerve: arises L1, L2; has femoral branch; genital branch enters inguinal canal, supplies cremaster muscle
lateral femoral cutaneous nerve of the thigh: arises L2, L3; supplies skin on anteriolateral thigh
femoral nerve: arises L2, L3; supplies psoas and iliacus muscles, extensor muscles of the thigh
obturator nerve: arises L2, L3, L4; supplies adductor muscles of the thigh
Diaphragm
blood supply through inferior phrenic arteries
innervation: phrenic nerves (C3, 4, and 5 keep the diaphragm alive)
origins: sternal: at xiphoid process
- costal: at the lower six ribs
- vertebral:
Þ runs from L1 transverse process to rib 12
medial arcuate ligament Þ runs from L1 transverse process to L1 vertebral body (crura of diaphragm)
median arcuate ligament Þ unites left and right crura of diaphragm
insertion: central tendon
vena caval foramen at T8 and is a hole in the central tendon
hiatus for esopahgus at T10; usually in the muscles of the right crus
aortic hiatus: posterior to the diaphragm at T12; posterior to the median arcuate ligament, between left and right crura
Suprarenal glands
venous drainage: IVC on right, renal vein on left
right gland is more triangular
glands are surrounded by fat
outer cortex is of gut origin and secretes corticosteroids
inner medulla is of neural crest origin and secretes epinephrine and norepinephrine
innervation from T6 - L2
Kidneys
right kidney is slightly lower than the left
right kidney may be palpable; left is usually not
covered by renal capsule (Glisson’s capsule) Þ perirenal fat Þ renal fascia (around kidney and suprarenal gland) Þ pararenal fascia
renal pyramids (18-20) drain to renal papillae Þ minor calyxes Þ major calyxes Þ renal pelvis Þ ureter
bifid ureter is fairly common: two ureters leave kidney and then coalesce
gonadal vessels originate medial to the ureter then cross laterally
stones most likely originate at pelvis or major calyx; pain can anywhere from ilius to the medial aspect of the leg
innervation by T10 - L1
Structures
Vessels
Gonadal (Ovarian or Testicular)
: arise from aorta, run along psoas muscle; supply testicles or ovaries
Veins: right drains to IVC; left drains to left renal vein
Renal Veins: lie anterior to arteries; left longer than right
Renal Arteries
Abdominal Aorta
Suprarenal Arteries: suprarenal blood supply from three sources
- Superior from Inferior Phrenic; Middle from Aorta; Inferior from Renal
Inferior Phrenic Arteries: supply diaphragm
Lumbar Arteries: small branches off of the aorta; analagous to the intercostal arteries
Common Iliac Arteries: bifrucation of the aorta at L4
Muscles
Psoas Major
Origin: transverse process of T12 thru L5
Insertion: lesser trochanter of the femur
Innervation: branches of L2 - L5
Action: leg flexion (with iliacus), torso flexion
Psoas Minor (50% of people)
Origin: T12 and L1
Insertion: iliopubic eminence
Innervation: ventral ramus of L1
Action: torso flexion
Iliacus
Origin: superior iliac crest and fossa
Insertion: lesser trochanter of the femur
Innervation: femoral nerve L2 - L4
Action: leg flexion (with psoas)
Quadratus Lumborum
Origin: inferior border to 12th rib; tips of lumbar transverse processes
Insertion: iliolumbar ligament and iliac crest
Innervation: branches of T12 - L4
Action: stabilizes 12th rib; lateral flexion
Kidney
Perirenal Fat: lies between kidney and renal fascia; also surrounds suprarenal glands
Ureters: drain renal pelvis to the urinary bladder
Sections
- Cortex
- Medulla
- Renal Pyramid
: contains collecting ducts; empties into renal papillae
- Renal Columns
: portions between renal pyramids
- Renal Papillae
: apex of renal pyramid; site where collecting ducts empty to minor calyx
- Minor Calyces
: usually 7 - 14; dump into major calyces
- Major Calyces
: usually two or three; dump into renal pelvis
- Renal Pelvis
: funnel shaped
Suprarenal Gland: right gland is triangular in shape; left is semilunar in shape
- Cortex
: lighter region; secretes steriod hormones
- Medulla
: darker; secretes norepinephrine and epinephrine
Diaphragm
right and left crura: musculotendinous structures arising from L1 - L3 vertabrae; joined superiorly and anteriorly by the median arcuate ligament forming the aortic hiatus
medial arcuate ligament: runs from transverse process of L1 to crus of the diaphragm
lateral arcuate ligament: runs from transverse process of L1 to the 12th rib
central tendon: insertion of all the muscle fibers of the diaphragm; hole just off right center forms vena caval foramen
esophageal hiatus: formed by splitting of the fibers of the lumbar part of the diaphragm
Nerves
subcostal nerve (12th thoracic nerve): supplies anterior abdominal wall between the umbilicus and pubic symphysis
iliohypogastric nerve: supplies skin of suprapubic and inguinal regions
ilioinguinal nerve: supplies skin of the inner thigh and scrotum
- iliohypogastric and ilioinguinal nerves arise from a common branch of L1
genitalfemoral nerve: arises L1, L2; has femoral branch; genital branch enters inguinal canal, supplies cremaster
lateral femoral cutaneous nerve of the thigh: arises L2, L3; supplies skin on anteriolateral thigh
femoral nerve: arises L2, L3; supplies psoas and iliacus muscles, extensor muscles of the thigh
obturator nerve: arises L3, L4; supplies adductor muscles of the thigh
Phrenic Nerve: from C3 - C5; keeps the diaphragm alive
Lumbosacral Trunk: large flat nerve; from L4, L5; forms part of the sacral plexus; is not a branch of the lumbar plexus
sympathetic trunk enters abdomen posterior to the medial arcuate ligament
- usually composed of five lumbar sympathetic ganglia
celiac plexus: on either side of the celiac trunk (solar plexus); contains celiac ganglia
greater splanchnic nerve: arises from ganglia at T6 - T 10