Lumbar and sacral plexuses. Nerve plexuses Networks of successive ventral rami that exchange fibers...
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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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29 Oct. 2012 Spinal-Nerves.ppt 9
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
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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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29 Oct. 2012 Spinal-Nerves.ppt 15
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
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Lumbosacral plexusSacral plexus:Sciatic nerve (roots):L4L5S1S2S3
*Sciatic nerve is the thickest nerve of body.*It is composed of Common Peroneal andTibial nerves.*Com. Peroneal: composed of dorsal rami Tibial: composed of ventral rami
*L4+L5= Lumbosacral trunk
3- Lumbosacral trunk4- Sciatic nerve5- common peroneal N.6- tibial N.12- posterior femoral cutaneous nerve13- pudendal nerve14- superior gluteal nerve
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Sacral plexus (L4-S4)
Sciatic nerve (L4-S3)
Tibial nerve
Common peroneal (fibular) nerve
Motor to muscles of pelvis and lower extremity (gluteal, posterior femoral, lower leg & foot)Sensory from posterior pelvis, posterior thigh, anterior, posterior & lateral leg
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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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femurmedial
lateral
Anterior compartment-
Extensors of the knee
Femoral Nerve
Medial compartment-
Adductors of the knee
Obturator Nerve
Posterior compartment-
Flexors of the knee
Sciatic Nerve
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L2
L3
L4
iliopsoas
Rectus femoris
pectineus
Vastus medialis
Vastus intermedius
sartorius
Vastus lateralis
Motor Branches of the
Femoral Nerve
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Adductus magnus
gracilis
Adductor longus
Adductor brevis
Motor Branches of the
Obturator Nerve
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L4
L5
S1
S2
S3
Semitendinosis
Biceps femoris
semimembranosus
Ham
strin
gs
Gastrocnemius and posterior compartment of the leg and foot
Tibial nerve
Common peroneal nerve Deep peroneal
nerveAnterior compartment of leg
Lateral compartment of leg
Superficial peroneal nerve
Motor Branches of the
Sciatic Nerve
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• Sacral plexus nerves:
(Be able to label sciatic, tibial and common fibular nerves)
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Diaphragm? Phrenic nerve C3-5
Arm and forearm extensors? Radial nerveMedial hand? Ulnar nerveLateral palm? Median nerve
Quad? Femoral nerve
Footdrop? Common fibular/peroneal nerve (branch of Sciatic nerve)
Cervical plexus C1-5
Brachial plexus C5-T1
Lumbar plexus L1-4
Sacral plexus L4-S4
Nerve plexuses (very) simplified….
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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