LUMBAR PLEXUS Flashcards
is found in the pelvic cavity, embedded for the most part in the psoas major muscle
it is formed from the ventral rami of L1-L4 (although T12 may contribute)
LUMBAR PLEXUS
is the term given to the nerve axons of L4 and L5 that allow communication between
the lumbar plexus and the sacral plexus
lumbosacral trunk
is common to both the lumbar and sacral plexus
L4
is found just lateral to the psoas major muscle
its segmental innervation is L1 (sometimes T12)
it is formed from the anterior division of the spinal nerves
it is the motor supply to the internal oblique and transverse abdominis muscles
it gives cutaneous supply to the skin covering the proximal lateral aspect of the buttocks**
Iliohypogastric Nerve
its segmental innervation is L1
come off of the anterior division of the L1
it has only cutaneous function and supplies skin covering the proximal medial aspect of the thigh
Ilioinguinal Nerve
enters the thigh by passing beneath the inguinal ligament, just medial to the anterior superior iliac spine
it gets its segmental innervation from L2 and L3
comes off of the posterior division of the spinal nerves that form it
it has only cutaneous function and supplies skin over the lateral aspect of the thigh (both anterior and
posterior)
Lateral (Femoral) Cutaneous Nerve of the Thigh
is a compression neuropathy of the lateral femoral cutaneous nerve as it leaves the pelvic cavity beneath
the inguinal ligament
symptoms include pain, burning and tingling sensations along the lateral aspect of the thigh
common causes of the condition include obesity, wearing tight fitting clothing or any activity which puts
the femur in a flexed position for long periods of time
the condition is sometimes confused with certain hip disorders i.e. trochanteric bursitis
Meralgia Paresthesia (Lateral Femoral Cutaneous Nerve Entrapment)
a nerve which pierces the psoas major muscle and runs inferiorly on the anterior aspect of the muscle
as the nerve descend it divides into a femoral and genital branch
its segmental innervation is L1 and L2
it come off of the anterior division of the spinal nerves that form it
the nerve gives motor supply to the cremaster muscle (found within the spermatic cord)
the nerve also gives cutaneous supply to the skin covering the genitalia and a small area below the
inguinal ligament
Genitofemoral Nerve
the femoral nerve is the largest branch of the lumbar plexus
it passes from the pelvic cavity to the thigh by going deep to the inguinal ligament
before the nerve leaves the pelvic cavity, it gives off some muscular branches and then terminates in the
thigh into several cutaneous and muscular branches
the segmental innervation of the nerve is L2 ,L3 and L4
it comes off the posterior division of the spinal nerves that form it
the nerve gives motor supply to the iliacus, psoas major, sartorius, quadriceps and pectineus muscles
the cutaneous supply of the supply is to the skin covering the medial and intermediate aspect of the
anterior thigh and the medial aspect of the leg and foot
the specific cutaneous branch of the nerve which supplies the skin covering the medial aspect of the leg
and foot is known as the saphenous nerve (which accompanies the femoral artery in the adductor canal)
the nerve gives off articular branches to supply the hip and knee joints
Femoral Nerve
Damage to the Femoral Nerve (Motor)
quadriceps are involved and the leg cannot be extended. Flexion of the hip is diminished (illiopsoas)
Damage to the Femoral Nerve
Sensory
medial and intermediate anterior aspect of the thigh –medial aspect of the leg and foot
may occur within the adductor canal or where it exits the fascia to
supply the medial leg; entrapment neuropathy of the saphenous can cause knee pain and paresthesia
along the distribution of the nerve
compression of the saphenous nerve
is the smaller and more medial of the two large terminal branches of the lumbar plexus
it passes from pelvic cavity to the medial aspect of the thigh by passing through an opening in the
membrane that covers the obturator foramen
its segmental innervation is L2,L3 and L4
the nerve is formed from the anterior division of the spinal nerve that form it
it is the motor supply to the pectineus, adductor magnus, adductor longus and brevis, gracilis and
obturator externus
cutaneous supply is to skin on the medial aspect of the thigh
articular supply to the hip and knee joints
Obturator Nerve
the nerve may be damaged during a difficult birth or by an anterior dislocation of the hip joint
if one suspects that the nerve has been compromised, adduction of the femur against resistance should
be tested
Damage to the Obturator Nerve
formed from L4 and L5 (lumbosacral trunk) and S1, S2, S3 and S4
the plexus lies largely on the piriformis muscle
the sacral nerves enter the pelvis via the anterior sacral foramina
much of the plexus innervates the lower extremity, but a number of branches supply structures within the
pelvis or perineum
SACRAL PLEXUS
its segmental innervation is from S1, S2 and S3
formed from the anterior and posterior divisions
has only cutaneous function which supplies skin covering the distal part of the buttocks, posterior thigh
and popliteal fossa
Posterior Femoral Cutaneous Nerve
leaves the pelvis via the superior part of the greater sciatic notch
its segmental innervation is L4,L5 and S1
formed from the posterior division of the spinal nerves that form it
motor supply to the gluteus medius, gluteus minimus and tensor fascia lata muscles
Superior Gluteal Nerve
leaves the pelvis via the inferior part of the greater sciatic notch
segmental innervation of the nerve is L5, S1 and S2
formed from the posterior division of the spinal nerves that form it
motor supply to the gluteus maximus muscle
Inferior Gluteal Nerve
this is the main sensory nerve to the external genitalia
it leaves the pelvic cavity via the greater sciatic notch
its segmental innervation is S2,S3,S4
formed from the anterior division of the nerves that form it
Pudendal Nerve
largest nerve in the body and is the continuation of the sacral plexus into the leg and foot
the nerve leaves the pelvic cavity through the greater sciatic notch, deep to the piriformis muscle
the segmental innervation of the nerve is L4,L5,S1,S2,S3
its motor supply is to the adductor magnus, semitendinosus, semimembranosus and biceps femoris
muscles
Sciatic Nerve
formed from the anterior division) and supplies the muscles and most of
the skin of the posterior leg and plantar surface of the foot
tibial nerve
division of sciatic n.
(formed from the posterior division) which wraps around the neck
of the fibula and has two branches (deep fibular and superficial fibular); the branches
supply the muscles and skin of the anterior leg, lateral leg and dorsum of the foot
common fibular nerve
division of the sciatic n.
3 ways the sciatic n. may be injured
Fracture of the pelvis bone
Posterior dislocation of the hip joint
Penetrating wounds (i.e. badly placed intramuscular injections)
Hamstring muscles are atrophied but weak flexion of leg is possible due to actions of the sartorius and grascilis. All muscles distal to the knee may be involved. The foot due to gravity falls into the plantar flexed position (foot drop)
with injury to the nerve the following clinical features may be noted: MOTOR
