Lumbar and sacral plexuses

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Lumbar and sacral plexuses
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Nerve plexuses

• Networks of successive ventral rami that exchange
  fibers (crisscross redistribute)
• Why would this be protective?
• Mainly innervate the limbs
• Thoracic ventral rami do not form nerve plexuses

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Plexuses

• Cervical
• Brachial
• Lumbar
• Sacral

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Lumbar plexus

• L1-L4
• Lies within the psoas major muscle
• Innervates anterior and medial muscles of thigh
  through femoral and obturator nerves respectively
• Femoral nerve also innervates skin on anterior
  thigh (including quads) and medial leg

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Diaphragm and posterior abdominal wall The psoas
major and minor muscles, the quadratus lumborum
muscle. The lumbar plexus and its related nerves.
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LUMBAR PLEXUS
Spinal nerves branching from the lumbar region of
the cord form the lumbar plexus. Branches of
this plexus stimulate muscles of the back, hip
and thigh. The plexus also is responsible for
sensation in the skin of the thighs, the pubic
area and the external genitalia in males and
females.
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LUMBOSACRAL SPINAL CORDPOSTERIOR VIEW
The area within the rectangle shows the lower
portion of the spinal cord. The branches leaving
the sacral region pass through the sacral
foramina forming the sacral plexus.
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Lumbar plexus

• L1 L4 ( L5)
• Ilioinguinal nerve
• mostly sensory from skin of thigh genitals
• Genitofemoral nerve
• mostly sensory from scrotum, labia majora, ant.
  Thigh
• Femoral Nerve
• to quadriceps, sartorius

29 Oct. 2012
Spinal-Nerves.ppt
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Lumbosacral plexus Lumbar plexus (T12- L4) 1-
Obturator nerve (L2-L3-L4) 2- Femoral nerve
(L2-L3-L4) 3- Lumbosacral trunk (L4-L5) 7-
subcostal nerve (T12) 8- iliohypogastric N.
(T12-L1) 9- ilioinguinal N. (L1) 10-
genitofamoral N. (L1-L2) 11- lateral cutaneous
N. of the thigh (L2-L3)
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Lumbar Plexus

• Femoral nerve
• Cutaneous branches
• Thigh, leg, foot (e.g. saphenous nerve)
• Motor branches
• Anterior thigh muscles (e.g. quadriceps,
  sartorius, iliopsoas)
• Obturator nerve
• Sensory
• Skin medial thigh hip, knee joints
• Motor
• Adductor muscles
• Lateral femoral cutaneous
• Sensory
• Skin lateral thigh
• Genitofemoral
• Sensory
• Skin scrotum, labia major, anterior thigh
• Motor
• Cremaster muscle

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Lumbar plexus(be able to label femoral,
obturator and saphenous nerves)
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SACRAL PLEXUS
Spinal nerves branching from the lumbar (L4 and
L5) and sacral (S1, S2, S3 and S4) region of the
cord form the sacral plexus. Nerves branching
from this plexus innervate the limb and pelvic
area. Because the lumbar and sacral plexuses are
interconnected, they are sometimes referred to as
the lumbosacral plexus.
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Sacral plexus

• L4-S4
• Supplies muscles and skin of posterior thigh and
  almost all of the leg
• Main branch is the large sciatic nerve, which
  consists of
• Tibial nerve to most of hamstrings, calf and
  sole
• Common fibular nerve to muscles of anterior
  and lateral leg and skin
• Other branches supply pelvic girdle (gluteus
  muscles) and perineum (pudental nerve)

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Sacral plexus

• L4 S4
• Superior inferior gluteal nerves
• To gluteus muscles
• Sciatic nerve
• To hamstrings other posterior thigh leg
  muscles
• Pudendal nerve
• Sensory from penis, clitoris, labia minora, anus

29 Oct. 2012
Spinal-Nerves.ppt
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Lumbosacral plexus Sacral plexus Sciatic nerve
(roots) L4 L5 S1 S2 S3 Sciatic nerve is the
thickest nerve of body. It is composed of Common
Peroneal and Tibial nerves. Com. Peroneal
composed of dorsal rami Tibial composed of
ventral rami L4L5 Lumbosacral trunk 3-
Lumbosacral trunk 4- Sciatic nerve 5- common
peroneal N. 6- tibial N. 12- posterior femoral
cutaneous nerve 13- pudendal nerve 14- superior
gluteal nerve
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Sacral plexus (L4-S4)
Motor to muscles of pelvis and lower extremity
(gluteal, posterior femoral, lower leg
foot) Sensory from posterior pelvis, posterior
thigh, anterior, posterior lateral leg

• Sciatic nerve (L4-S3)
• Tibial nerve
• Common peroneal (fibular) nerve

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SCIATIC NERVE
The sciatic nerve (astrerisk) is formed from
spinal nerves arising from the lumbar (L4 and L5)
and sacral (S1, S2 and S3) regions of the spinal
cord. It passes into the thigh and lower leg
supplying innervation of sensation and movement
for the entire lower limb. When giving a gluteal
intramuscular injection, it is important to
inject into the gluteus medius muscle to avoid
damage to this large nerve.
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Sacral Plexus

• Sciatic
• Motor
• Hamstring
• Branches into
• Tibial nerve
• Cutaneous
• Posterior leg and sole of foot
• Motor
• Posterior leg, foot
• Common fibular (peroneal) nerve
• Cutaneous
• Anterior and lateral leg, dorsum foot
• Motor
• Lateral compartment, tibialis anterior, toe
  extensors
• Superior gluteal nerve
• Motor
• Gluteus medius and minimus, tensor fasciae latae

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Sacral Plexus (continued)

• Inferior gluteal nerve
• Motor
• Gluteus maximus
• Posterior femoral cutaneous nerve
• Sensory
• Inferior buttocks, posterior thigh, popliteal
  fossa
• Pudendal nerve
• Sensory
• External genitalia, anus
• Motor
• Muscles of perineum

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• The only one of the three that travel below the
  knee is the sciatic nerve.
• The sciatic nerve branches into two nerve
• 1. tibial nerve
• 2. common peroneal nerve
• a. Superficial peroneal nerve
• b. Deep peroneal nerve

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Anterior compartment- Extensors of the
knee Femoral Nerve
lateral
femur
medial
Medial compartment- Adductors of the
knee Obturator Nerve
Posterior compartment- Flexors of the
knee Sciatic Nerve
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Motor Branches of the Femoral Nerve
L2 L3 L4
Rectus femoris
iliopsoas
pectineus
sartorius
Vastus lateralis
Vastus medialis
Vastus intermedius
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Motor Branches of the Obturator Nerve
Adductor brevis
Adductor longus
gracilis
Adductus magnus
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Motor Branches of the Sciatic Nerve
L4 L5 S1 S2 S3
Semitendinosis Biceps femoris semimembranosus
Hamstrings
Common peroneal nerve
Tibial nerve
Deep peroneal nerve
Anterior compartment of leg
Superficial peroneal nerve
Gastrocnemius and posterior compartment of the
leg and foot
Lateral compartment of leg
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• Sacral plexus nerves
• (Be able to label sciatic, tibial and common
  fibular nerves)

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Nerve plexuses (very) simplified.
Cervical plexus C1-5 Brachial plexus
C5-T1 Lumbar plexus L1-4 Sacral plexus
L4-S4

• Diaphragm?
• Phrenic nerve C3-5
• Arm and forearm extensors?
• Radial nerve
• Medial hand?
• Ulnar nerve
• Lateral palm?
• Median nerve
• Quad?
• Femoral nerve
• Footdrop?
• Common fibular/peroneal nerve
• (branch of Sciatic nerve)

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Dermatomes (innervation of skin)
Dermatomes (area of skin innervated by the
cutaneous branches from a single spinal nerve is
called a dermatome) Reveal sites of
damage to spinal nerves or spinal cord