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Nerves of posterior abdominal
wall(spinal nerves): Lumbar Plexus
It is formed from anterior (ventral)
rami of upper 4 lumbar nerves.
Site :
It is formed within the substance of
psoas major muscle.
Its branches emerge from lateral &
medial borders of the muscle and its
anterior surface.
It is one of the main nervous
supplying the lower limb.
All anterior rami receive gray rami
communicantes from sympathetic
trunk, and the upper 2 lumbar nerves
give off white rami communicantes to
symp. trunk.
Branches of Sympathetic trunk (Abdominal part) :
White rami communicantes :
the upper 2 ganglia receive a white rami
communicantes from 1st & 2nd lumbar
spinal nerves, they contain
preganglionic N.Fs. & sensory N.Fs.
Gray rami communicantes
(postganglionic Fs.) to all
A- N.Fs. Synapse in a symp.chain
ganglion at same level.
B- N.Fs. synapse in a symp.chain
ganglion at a different level.
C- N.Fs. Synapse in a collaterl (aortic)
ganglion as sup.mesenteric ganglion.
lumbar spinal nerves. A grey ramus
contains postganglionic N.Fs. These
Fs.are distributed through the branches
of spinal nerves to skin :
1-blood vessels (vasomotor)
2-sweat glands
3-arrector pili muscles of skin.
Branches of Lumbar plexus
Iliohypogastric, ilioinguinal,
lateral cutaneous N. of thigh and femoral
N. emerge from lateral border of psoas
muscle, in order that from above
Iliohypogastric & ilioinguinal nerves
(L1) :
-Iliohypogastric skin of lower
part of anterior + lateral abdominal wall,
-ilioinguinal N. passes through inguinal
canal to supply skin of groin (upper
medial part of thigh) + scrotum or labium
Lateral cut.N. of thigh (L2,3) : passes
in front of iliacus muscle and enter thigh
behind lateral end of inguinal ligament to
supply skin of lateral surface of thigh.
Branches of Lumbar plexus
Femoral N. ( dorsal division of
ventral rami of L2,3,4): is the largest
branch of lumbar descends
between psoas & iliacus and enters thigh
behind inguinal lig. and lateral to femoral
vessels & sheath.
-In abdomen : It supplies iliacus +psoas
-In lower limb : It supplies muscles of front
of thigh + skin of anterior & lateral surface
of thigh + skin of medial side of leg & foot
through saphenous N.
Obturator N. (ventral division of
ventral rami of L2,3,4) : emerge from
medial border of psoas muscle. it
descends in front of sacroiliac joint and
behind common iliac vessels in the
pelvis. It enters thigh through obturator
Branches of Lumbar plexus
4th lumbar root of lumbosacral trunk
: -it takes part in sacral plexus
-it descends anterior to ala
of sacrum to join 1st sacral nerve.
Genitofemoral nerve (L1,2) :
-emerges from anterior surface of psoas
-it descends in front of psoas and above
inguinal ligament it divides into genital
branch, which enters spermatic cord
and supplies cremaster muscle + skin of
scrotum, and a femoral branch, which
supplies a small area of skin in the
uppermost part of front of thigh.
-Genitofemoral nerve is involved in
cremateric reflex, in which stimulation of
skin of thigh in male results in reflex
contraction of cremaster muscle and
drawing upward of testis within the scrotum,
Lymph Nodes of posterior
They are closely related to aorta to
abdominal wall:
form a preaortic and a right & left
lateral aortic (para-aortic or lumbar)
Preaortic L.Ns. lie around origins of
celiac, superior mesenteric,and inferior
mesenteric arteries. They drain lymph
from G.I.T.from lower 1/3 of esophagus
to halfway down anal canal, and also
from spleen, pancreas,gallbladder &
liver. Efferent lymph vessels form large
intestinal lymph trunk.
Lateral aortic (para-aortic or
lumbar) L.Ns.: drain lymph from
kidneys & suprarenals, from testes or
ovaries, uterine tubes & fundus of
uterus, from deep lymph vessels of
abdominal walls, and from common
iliac Ns. Efferent lymph vessels form
right & left lumbar trunks.
Lymph vessels of posterior
abdominal wall:
Cisterna chyli :
-it is a narrow sac , opens upwards
into thoracic duct.
–it collects lymph from abdomen &
lower limbs.
-Tributaries : it receives intestinal
trunk, right & left lumbar trunks and
some lymph vessels from lower
Thoracic duct : begins in the
abdomen as an elongated lymph
sac, cisterna chyli, which lies
below diaphragm, in front of first 2
lumbar vertebrae and on right site
of aorta.
Thoracic duct
It runs upward to enter
thorax through aortic opening
of diaphragm, then into root
of neck to end in
left brachiocephalic vein.
It conveys all lymph from
lower limbs, pelvic cavity,
abdominal cavity, left side of
thorax + left side of head,neck
& left upper limb to blood of
left brachio-cephalic vein.
(A),Tributaries of thoracic duct & right lymphatic
(B), The areas of body drained into thoracic duct
(clear) and right lymphatic duct (black).
The right side of head ,neck
& right uper limb are drained
by right lymph trunk into
right brachio-cephalic vein.
Structures of pelvic walls
Anterior pelvic wall : it is a
shortest wall, it is formed by :
-posterior surface of pubic bodies
-symphysis pubis.
 posterior pelvic wall : It is
formed by :
–sacrum & coccyx.
-Piriformis muscle.
-Parietal pelvic fascia which covers
bones & piriformis muscles.
Piriformis muscle
Origin : front of middle 3 pieces
(S2,3,4) of sacrum.
Insertion : it leaves pelvis to
enter gluteal region by passing
through greater sciatic foramen to
be inserted into top (upper border)
of of greater trochanter of femur.
N.suply : branches from sacral
plexus (S1,2).
Action : lateral rotator of femur
at hi joint.
Structures of Pelvic walls
Lateral pelvic wall : it consists of :
-Part of hip bone below pelvic inlet.
-Obturator membrane.
-Obturator internus & its covering fascia.
-Sacrotuberous & sacrospinous ligaments.
Inferior pelvic wall (Pelvic floor ) or
(pelvic diaphragm) :
-it supports pelvic viscera, it divides pelvis
into :
-upper part : it is the main pelvic cavity.
-lower part : it is the perineum (structures
that fill outlet of true pelvis)
-pelvic floor is formed of :
1-levator ani muscles.
2-coccygeus muscles.
3-fascia covering these muscles.
-the pelvic floor is incompletle anteriorly
to allow passage of urethra in male +
urethra & vagina in female.
Pelvic walls
Sacrotuberous ligament : is strong.
–its medial upper end is attched to :
1-posterior inferior iliac sine.
2-lateral surface of sacrum & coccyx.
-its lateral lower end : is attached to :
1-medial margin of ischial tuberosity.
Sacrospinous ligament : is a strong
triangular ligament.
-its apex : is attached to ischial spine.
-its base : is attched to last piece of
sacrum + first piece of coccyx.
The function of 2 ligaments :
1-they convert greater & lesser sciatic
notches into foramina, greater & lesser
sciatic foramina. 2- they prevent lower end of
sacrum & coccyx from being rotated upwards
at sacroiliac joint by the weight of body.
Obturator membrane, Canal
 obturator membrane : is
& muscle :
completely closes the obturator
foramen except at the upper part where
it leaves a small gap called obturator
Obturator N. & vessels leave the
pelvis to enter thigh by passing through
obturator canal.
Obturator internus muscle :
-origin : pelvic surface of obturator
membrane + adjoining part of hip bone.
-insertion : its tendon leaves pelvis
through lesser sciatic foramen to be
inserted into upper border of greater
trochanter of femur. : obturator internus
(sacral plexus).
-action : lateral rotation of thigh at hip
Obturator Fascia
It is a part of parietal pelvic fascia.
It covers pelvic surface of
obturator internus muscle.
A tendinous arch is formed by
thickening of pelvic fascia
(obturator fascia) covering the
obturator internus, and gives a
linear origin for levator ani muscle.
Levator ani muscle
It is a wide thin sheet that has
linear origin from :
1-back of body of pubis.
2-obturator fascia (tendinous arch).
3-ischial spine.
Insertion : by 3 fibres.
1-anterior fibres :
(levator prostatae or sphincter
vaginae). : form a sling around
prostate or vagina and inserted into
perineal body in front of anal canal
(a mass of fibrous tissue). its
function is to support the prostate
or to constrict the vagina + to
stabilize the perineal body.
Levator ani muscle
Intermediate fibres :
1-(puborectalis) : it forms a sling
around the junction of rectum &
anal canal to meet other fibres.
2-(Pubococcygeus) : passes
posteriorly to be inserted into anococcygeal body,
(a small fibrous mass) between tip
of coccyx & anal canal.
Posterior fibres :
( iliococcygeus) : passes
posteriorly to be inserted into anococcygeal body & coccyx.
Pelvic Walls
The bony pelvis consists of 4 bones :
- 2 hip bones : form lateral & anterior
- Sacrum & coccyx : form posterior wall.
Pelvic brim : is formed by
- Sacral promontory : posteriorly.
- Ilio-pectineal lines : laterally.
- Symphysis pubis : anteriorly.
 Sacral promontory : is the projecting
forwards of the anterior margin of body of S1
Parts of pelvis :
1-False (greater) pelvis : above pelvic
brim, it forms part of abdominal cavity, it
consists mainly of right & left iliac
2-True (lesser) pelvis : below pelvic
brim, it is a curved canal which has an
inlet, outlet & a cavity.
Pelvic walls
Pelvic inlet : is formed by
boundaries of pelvic brim.
Pelvic outlet :
-coccyx : posteriorly.
-ischial tuberosities + sacrotuberous
ligament : laterally.
-pubic arch + symphysis ppubis :
Pelvic cavity : it is a curved canal,
lies between inlet & outlet, and has a
short anterior wall and longer posterior