LUMBAR AND SACRAL PLEXUSES

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

PLEXUSES Cervical Brachial Lumbar Sacral

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

Diaphragm and posterior abdominal wall: The psoas major and minor muscles, the quadratus lumborum muscle. The lumbar plexus and its related nerves. 5

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.

LUMBOSACRAL SPINAL CORD POSTERIOR 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.

Lumbar Plexus L1 – L4 (+ L5) Ilioinguinal nerve Genitofemoral nerve mostly sensory from skin of thigh & genitals Genitofemoral nerve mostly sensory from scrotum, labia majora, ant. Thigh Femoral Nerve to quadriceps, sartorius 9

LUMBAR PLEXUS (T12- L4): Obturator nerve (l2-l3-l4) Femoral nerve (l2-l3-l4) Lumbosacral trunk (l4-l5) Subcostal nerve (t12) Iliohypogastric n. (T12-l1) Ilioinguinal n. (L1) Genitofamoral n. (L1-l2) Lateral cutaneous n. of the thigh (l2-l3) 10

Lumbar Plexus Femoral nerve Obturator nerve Lateral femoral cutaneous 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 Skin lateral thigh Genitofemoral Skin scrotum, labia major, anterior thigh Cremaster muscle

Lumbar plexus ( femoral, obturator and saphenous nerves)

Femoral nerve branches Course : Largest nerve of lumber plexus It emerges from lateral border of psoas muscle in the abdomen Passes downward in the interval between psoas and iliacus It lies behind fascia iliaca & enter the thigh lateral to femoral artery and femoral sheath behind the inguinal ligament. About 1.5 inch below the inguinal ligament it terminates by dividing into ant. And post. Divisions..

Branches of femoral nerve Anterior division 2 cutaneous nerves 1)medial cutaneous 2)intermediate cutaneous 1)nerve to sartorious 2)nerve to pectenius 2 muscular branches

Branches of femoral nerve Posterior division 1 cutaneous nerve Saphanous nerve Muscular branches to quadriceps

Obturator nerve Arises from lumber plexus L2,L3,L4. Emerges on the medial border of psoas muscle within the abdomen. Runs forward on the lateral wall of pelvis to reach the upper part of obturator foramen where it divides into ant. &post. Divisions. Anterior division passes in front of obturator externus & adductor brevis and behind pectineus and adductor longus. Muscular branches to gracillis,adductor brevis,adductor longus, occasionally to pectineus

Branches of obturator nerve Posterior division pierces the obturator externus and passes downward behind adductor brevis and infront of adductor magnus. It terminates by entering the gap between adductor magnus and supplying the knee joint

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.

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 (pudendal nerve)

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

Sciatic nerve (roots): L4, L5, S1, S2, S3 LUMBOSACRAL 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 *L4+L5= 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 23

Sacral plexus (L4-S4) Sciatic nerve (L4-S3) Tibial 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 Sciatic nerve (L4-S3) Tibial nerve Common peroneal (fibular) nerve

Sciatic nerve Course and distribution Branch of sacral plexus L4,5,S1,2,3. Leaves the gluteal region as it descends in the midline of the thigh. Overlapped posteriorly by adjacent margins of biceps femoris & semimembranosus. Lies on the posterior aspect of adductor magnus. In the lower 3rd of thigh it ends by dividing into the tbial and common peroneal nerve.

Tibial nerve Larger terminal branch Lies superficial to popliteal vessels Extends from sup. Angle to inf. Angle of popliteal fossa Muscular branches Cutaneous branch(sural nerve) Three genicular branches.. Sup.medial, inf.med, medial. Runs downward &laterally, winds around lateral border of politeus

Tibial nerve terminate by dividing into medial &lateral planter nerve Crosses post. Tibial artery from medial to lateral side Musular branches to tibialis post,flexor digitorum longus.flexor hellucis longus, deep part of soleus Medial calcaneam branch supply the skin of back &lower surface of heel Articlar branch to ankle joint

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.

Sacral Plexus Sciatic Tibial nerve Cutaneous (SURAL NERVE) Motor: Hamstring Branches into: Tibial nerve Cutaneous (SURAL NERVE) Posterior leg and sole of foot Motor Posterior leg, foot ARTICULAR TO KNEE JOINT Common fibular (peroneal) nerve Cutaneous (SURAL COMMUNICATING NERVE) Anterior and lateral leg, dorsum foot Lateral compartment, tibialis anterior, toe extensor

Summary

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

Anterior compartment- Extensors of the knee Femoral Nerve lateral medial femur Medial compartment- Adductors of the knee Obturator Nerve Posterior compartment- Flexors of the knee Sciatic Nerve

Motor Branches of the Femoral Nerve L2 L3 L4 Rectus femoris iliopsoas pectineus sartorius Vastus lateralis Vastus medialis Vastus intermedius

Motor Branches of the Obturator Nerve Adductor brevis Adductor longus gracilis Adductus magnus

Motor Branches of the Sciatic Nerve Hamstrings Common peroneal nerve Semitendinosis Biceps femoris semimembranosus Hamstrings Common peroneal nerve Tibial nerve Deep peroneal nerve Superficial peroneal nerve Anterior compartment of leg Gastrocnemius and posterior compartment of the leg and foot Lateral compartment of leg

Sacral plexus nerves: (Be able to label sciatic, tibial and common fibular nerves)

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)

Dermatomes (innervation of skin) (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 Dermatomes (innervation of skin)

NERVES OF GLUTEAL REGION SUP. Gluteal nerve INF. Gluteal nerve Sciatic nerve Post,cutan. Nerve of thigh Nerve to quadratus femoris Pudendal nerve Nerve to obturatur internus Perforating cutan. Nerve of thigh

Cutaneous nerve supply