Muscles & bones forming the
posterior abdominal wall :
The post. abd. Wall is formed by :
1- 5 lumbar vertebrae &
intervertebral discs.
2- 12th rib & 2 iliac bones.
3- psoas muscles , quadratus
lumborum muscles , iliacus muscle,
aponeuroses of origin of transversus
abdominis muscles & posterior part
of diaphragm.
Psoas Major muscle :
Origin :
transverse processes , sides of bodies &
intervertebral discs of 12th thoracic & the 5
lumbar vertebrae.
Insertion :
with iliacus into the lesser trochanter of
femur, by passing behind inguinal ligamen.
Nerve supply : lumbar plexus(L1,2,3)
Action :flexes thigh on trunk at hip joint
& if thigh is fixed , it flexes the trunk on
thigh , as in sitting up from lying position.
The psoas is enclosed in a fibrous sheath
derived from the lumbar fascia, this sheath
is thickened above forming medial arcuate
ligament.
Psoas Minor Muscle :
It is a small unimportant muscle,
absent in 40% of people, if it is
present it lies in front of psoas
major
Origin : adjacent sides of bodies
of T12 & L1 vertebrae & disc
between them.
Insertion : iliopectineal eminence
& pectineal line.
N.Supply : ventral ramus of L1
N.
Action : Flexion of lumbar part of
Quadratus Lumborum muscle :
Origin : iliolumbar ligament , iliac crest ,
tips of transverse processes of lower 2-3
lumbar vertebrae.
Insertion : lower border of 12th rib &
upper 4 lumbar vertebrae.
Nerve supply : lumbar plexus(L1,2,3,4).
Action : fixation of 12th rib to help
contraction of diaphragm during deep
inspiration– depresses 12th rib during forced
expiration – lateral flexion of vertebral
column on the same side.
It is covered by lumbar fascia , which is
thickened above forming lateral arcuate
ligament , and below forming iliolumbar
ligament.
Iliacus muscle :
Origin : iliac fossa
Insertion : with the psoas major
tendon.... into the lesser trochanter of
femur. The combined muscles are called
iliopsoas.
Nerve supply : femoral N. (branch of
lumbar plexus).
Action : 1-iliopsoas flexes the thigh on
trunk at hip joint , or
if the thigh is fixed…
2-.It flexes the trunk on thigh.
(as psoas major ).
Fascial lining of the abdominal walls
The abdominal walls are lined
by one continuous layer of
C.T.that lies between parietal
peritoneum & abdominal muscles
It is continuous below with a
pelvic fascia lining pelvic walls.
Abdominal blood & lymph vessels
lie within fascial lining, while nerves lie
outside the fascia as in femoral sheath.
Its name is according to
structure it overlies.
Diaphragmatic fascia covers
undersurface of diaphragm,
transversalis fascia lines
transversus abdominis,
psoas fascia covers psoas muscle,
Quadratus lumborum fascia
covers Q.L.muscle &
iliaca fascia covers iliacus muscle.
Thoraco-lumbar Fascia :
It is a deep fascia which covers and
encloses the muscles of the back.
Lumbar part of deep fascia lies in
interval between iliac crest & 12th rib.
Laterally : it gives origin to :
1-middle Fs.of transversus abdominis.
2-upper Fs. of internal oblique.
Medially : it splits into 3 lamellae or
layers :
Anterior + middle layers,
extend superiorly to last rib & inferiorly to
iliac crest, & (enclose Q.L.muscle).
Posterior layer extends upwards to thorax
& neck & (enclose erector spinae muscle).
lumbar Fascia
Posterior layer :
-it covers back of erector spinae ms
–it extends from sacrum to neck.
-in the lumbar region , it is very
thick & attached to lumbar spines.
Middle layer :
-it covers back of Q.L.muscle.
-Medially, it attached to transverse
processes of lumbar vertebrae.
-Laterally it unites with post. layer
to give origin to int.oblique ms. &
with anterior layer to give origin to
transversus abdominis ms.
Q.L.muscle is enclosed between
anterior & middle layers of
thoraco-lumbar fascia.
Anterior layer : -it lies in front of
Q.L.ms. -medially, it is attached to the
lumbar transvese processes. -laterally : it
fuses with middle layer to give origin to
middle Fs. of transversus abdominis ms.
Fascia of psoas & iliacus
It is the fascial sheet covering the
ventral aspects of psoas & iliacus.
Above iliac crest :
-it covers psoas ms. Only.
- Medially, it is attached to lumbar
vertebrae & fused laterally with
anterior layer of thoraco-lumbar
fascia
Below iliac crest :
-it is called fascia iliaca as it covers
psoas & iliacus.
Fascia iliaca
Below iliac crest :
Medially : it is attached to pelvic
brim (sacral promontory + pectineal
line + sympysis pubis).
Laterally : it is attached to iliac crest.
-inferiorly , Behind inguinal lig. :
- its lateral part : it fuses with fascia
transversalis behind lateral part of
inguinal lig,
-but its medial part descends to the
thigh behind femoral vessels to form
post. wall of femoral sheath.
Iliopsoas Fascia and Tuberculosis :
T.B. disease of thoracolmbar region of vertebral
column. results in destruction
of vertebral bodies with
possible extension of pus
laterally under the psoas &
iliac fascia to appear as a
swelling below the inguinal
ligament ( may be mistaken
for femoral hernia).
Relations of Psoas Major muscle :
Inside its substances, Lumbar
plexus is formed.(L1,2,3,4).
Anteriorly : it is covered by psoas
fascia, psoas minor and is related to:
kidney, ureter, renal vs., gonadal vs.,
genitofemoral N.
Posteriorly : lumbar transverse
processes + medial edge of Q.L.
Medially : lumbar vertebral bodies,
lumbar vs., & symp.trunk.
Laterally : these Ns. emerge from its
lateral border : iliohypogastric N.,
ilioinguinal N., lat.cut.N.of thigh &
femoral N., which lies in deep groove
between psoas major & iliacus.
Relations of Quadratus lumborum
muscle :
Anteriorly :
1- it is covered by Q.L.fascia .
2-it is closed between anterior &
middle layers of thoracolumbar fascia.
3-subcostal vs.&N., iliohypogastric &
ilioinguinal nerves.
4-psoas major & minor.
5-colon & kidney.
Posteriorly : erector spinae
muscle.
Relations of Iliacus muscle :
Anteriorly :
1-fascia iliaca.
2-lateral cut.N. of thigh.
3-Rt.muscle is related to caecum,
while Left muscle is related to
descending & pelvic colon.
Posteriorly : iliac fossa.
Medially : Psoas major + femoral
N. ( in deep groove between psoas &
iliacus ).