Sciatic Nerve Pathway PDF

Sciatic Nerve Pathway Carley Bell 1. What plexus is the sciatic nerve on? 2. What nerve roots does the sciatic nerve carry? 1. Sacral plexus 2. L4-S3  The sciatic nerve conveys fibers from all spinal segments/nerves contributing to the sacral plexus (L4–S3) (Fig. 7.21E). It desc...

Sciatic Nerve Pathway Carley Bell 1. What plexus is the sciatic nerve on? 2. What nerve roots does the sciatic nerve carry? 1. Sacral plexus 2. L4-S3  The sciatic nerve conveys fibers from all spinal segments/nerves contributing to the sacral plexus (L4–S3) (Fig. 7.21E). It descends in the posterior compartment of the thigh, separating into its two components proximal to the knee. Its tibial nerve component supplies the extensor of the hip joint, flexors of the knee joint (with one exception), and plantar flexors of the ankle joint located in the posterior compartments of the thigh and leg (Fig. 7.21E, H). Immediately distal to the medial malleolus, it divides into medial and lateral plantar nerves that supply the skin and muscles of the sole of the foot (Fig. 7.21I, K). The common fibular nerve component of the sciatic nerve supplies the short head of the biceps muscle in the posterior compartment of the thigh (Fig. 7.21E). It winds around the neck of the fibula, dividing into (1) the superficial fibular nerve, supplying the evertors of the foot in the lateral compartment of the leg, and skin of the distal part of the lateral leg and the dorsum of the foot (Fig. 7.21F, G); and (2) the deep fibular nerve that supplies the dorsiflexors of the ankle joint located in the anterior compartment of the leg, the muscles of the dorsum of the foot, and the skin of the web between great and 2nd toes. The tibial and common fibular nerves form a common cutaneous nerve, the sural nerve (Fig. 7.21E). Prior to the merging of their branches, the medial (tibial) sural nerve supplies skin of the posterior leg, the lateral (fibular) sural nerve supplies skin of the lateral leg and dorsum of foot, and the common sural nerve supplies skin of the posterior ankle region and heel of foot (Fig. 7.21E–G, J–K).  First things first After coming off the sacral plexus, the sciatic nerve has a tibial division and a common fibular division that run TOGETHER The sciatic nerve runs through the posterior compartment of the thigh Posterior thigh (L5 - S2) The posterior compartment of the thigh includes - Semitendinosus - Semimembranosus - Biceps femoris long head - Biceps femoris short head ALL of these are innervated by the sciatic nerve - Semitendinosus, semimembranosus, and biceps femoris LH = tibial division - Biceps femoris short head = common fibular division Another thigh innervation? The hamstring part of the adductor magnus is also innervated by the tibial division of the sciatic nerve (L4) Sciatic nerve splits into tibial nerve and common fibular nerve at the top of the popliteal fossa Popliteal Fossa Popliteal Fossa Contents + Sural nerve branches + Small saphenous vein  Tibial Nerve Innervates the posterior compartment of the leg Superficial (S1-S2) - Gastrocnemius - Soleus - Plantaris Deep - Popliteus (L4-S1) - FDL (S2-S3) - FHL (S2-S3) - Posterior tibialis (L4-L5) Tibial Nerve - cutaneous Gives off a sural nerve branch that supplies the posterior leg (medial sural nerve) Medial sural nerve posterior  Tibial nerve splits into medial and lateral plantar nerves Medial plantar nerve (S2-S3) Lateral plantar nerve (S2-S3) - Abductor hallucis - Abductor digiti minimi - Flexor digitorum brevis - Quadratus plantae - Lumbrical 1 - Lumbricals 2,3,4 - Flexor hallucis brevis - ADDuctor hallucis - Flexor digiti minimi - Plantar interossei (3) - Dorsal interossei (4) Tibial Nerve - Cutaneous Gives off 3 branches that supply the foot - Medial plantar - Lateral plantar - Calcaneal Common Fibular Nerve - cutaneous Gives off a sural nerve branch that supplies the lateral leg (lateral sural nerve) lateral sural nerve lateral sural nerve  Common Fibular Nerve splits into deep and superficial fibular nerves Deep fibular nerve innervates Superficial fibular nerve innervates anterior compartment of the leg lateral compartment of the leg (L5-S1) (L5-S2) - EDL - Fibularis longus - EHL - Fibularis brevis - Fibularis tertius - EDB - EHB - Tibialis anterior (L4-L5)  Common Fibular Nerve splits into deep and superficial fibular nerves Deep fibular nerve cutaneously innervates - Webspace between digits 1 and 2 Superficial fibular nerve cutaneously innervates - Lower lateral leg and dorsum of the foot Common Sural Nerve Formed from the joining of medial and lateral sural nerves (via the sural communicating branch of the lateral sural nerve) Supplies skin of the posterior ankle region, heel of foot, and partially on the lateral foot Sural Communicating Branch branch of the common fibular nerve that joins with the medial sural cutaneous nerve to form the sural nerve Light blue = lateral sural from common fibular n Light green higher up = medial sural from tibial n Light green lower into ankle and foot = common sural from the joining of lateral/medial  Motor Summary Tibial division Medial plantar nerve (S2-S3) - Semimembranosus L5-S2 - Abductor hallucis - Flexor digitorum brevis - Semitendinosus L5-S2 - Lumbrical 1 - LH biceps femoris L5-S2 - Flexor hallucis brevis - HS part of adductor magnus L4 Lateral Plantar nerve (S2-S3) Tibial nerve - Abductor digiti minimi - Gastrocnemius S1-S2 - Quadratus plantae - Soleus S1-S2 - Lumbricals 2,3,4 - Plantaris S1-S2 - ADDuctor hallucis - Popliteus L4-S1 - FDL S2-S3 - Flexor digiti minimi - FHL S2-S3 - Plantar interossei (3) - Posterior tibialis L4-L5 - Dorsal interossei (4)  Motor Summary Common fibular division - SH biceps femoris L5-S2 Deep fibular nerve Superficial fibular nerve - EDL L5-S1 - Fibularis longus L5-S2 - EHL L5-S1 - Fibularis brevis L5-S2 - Fibularis tertius L5-S1 - EDB L5-S1 - EHB L5-S1 - Tibialis anterior L4-L5  Cutaneous Summary Tibial nerve Common fibular division - Medial sural n. (post leg) - Lateral sural n. (lower lateral leg) - Calcaneal n. (heal) - Medial plantar n. (sole) - Lateral plantar n. (sole) Deep fibular nerve - Web space between digits 1 Common fibular + tibial combined and 2 - Sural n. (post ankle region) Superficial fibular nerve - Lower lateral leg and dorsum of the foot