Lumbosacral Plexus Anatomy PDF

Prof Dr MT LUMBOSACRAL PLEXUS Combination of Lumbar And Sacral Plexus plexus THE LUMBAR PLEXUS §Within the psoas major m §Formed by the ventral rami of L1-3 & the s...

Prof Dr MT LUMBOSACRAL PLEXUS Combination of Lumbar And Sacral Plexus plexus THE LUMBAR PLEXUS §Within the psoas major m §Formed by the ventral rami of L1-3 & the sup part of L4 spinal nn §%50 of cases show a contribution from T12 (subcostal n) Lumbar Plexus  The largest branches of the LP (L2-4) o Obturator nerve o Femoral nerve Obturator n (L2, L3, L4) descends through the psoas major muscle pierces the psoas fascia crosses the sacroiliac joint emerges from the obturator canal takes cutaneous innervation of medial part of thigh motor innervation to the adductor muscles of thigh Femoral n (L2, L3, L4) emerges between the psoas major and iliacus m thickest branch Cutaneous branches: Medial cutaneous n of thigh Intermediate cutaneous n of thigh Saphenous n Motor branches: Muscles located at the anterior part of thigh Pectineus muscle  Iliohypogastric n & Ilioinguinal n are both derived from T12-L1-often by a common stem Iliohypogastric n (T12, L1) sends a “lateral branch” to supply the skin of the gluteal region “ant. branch” to the skin of the hypogastric region  Ilioinguinal n (T12,L1) passes through the superficial inguinal ring the skin of the groin Scrotum OR labium majus pudendi  Genitofemoral n (L1,L2) runs anterior surface of the psoas major muscle – femoral branch – genital branch (inguinal canal)  Lateral femoral cutaneous n (L2, L3) passes through the psoas major muscle, iliac crest  Lateral femoral cutaneous n (cont.) supplies skin over the ant-lat thigh  Lumbosacral Plexus nerve plexus in lumbar and sacral region the ventral rami L1-L3 nerves and the superior branch of L4 form the LUMBAR PLEXUS inferior branch of L4 and all L5 form the LUMBOSACRAL TRUNK and it descends to the SACRAL PLEXUS  Sacral is located in the lesser pelvis (true pelvis) it is closely related to the piriformis muscle Plexus is formed by the – lumbosacral trunk – ventral rami of the S1-3 – part of S4 Sacral Plexus  Sacral plexus All branches of SP leave the pelvis through the greater sciatic foramen- except for n to piriformis m  Sciatic nerve (L4, L5, S1, S2, S3) main branch of sacral plexus it is the largest nerve converge on the anterior surface of piriformis muscle enters the gluteal region and passes through the greater sciatic foramen  Sciatic nerve (cont.) it usually supplies no structures in the gluteal region Sciatic nerve has 2 terminal branches: o Tibial o Common fibular (peroneal) Superficial peroneal Deep peroneal  Sciatic nerve (cont.) § Tibial n § Common fibular (peroneal) n § They are bound together in the same epineurium (They usually separate from each other halfway of the thigh)  Pudendal n (S2, S3, S4) it is most medially located at the inferior edge of the piriformis m it innervates the structures in the perineum  Posterior femoral cutaneous n (S2, S3) it supplies cutaneous innervation of the o inferior part of the gluteal region o posterior side of the thigh and proximal part of the leg passes through infrapiriform foramen  Superior gluteal n (L4, L5, S1) passes through the greater sciatic foramen (suprapiriform foramen) along the superior gluteal vessels innervates the gluteus medius, minimus, and tensor fascia lata m  Inferior gluteal n (L5, S1, S2) Leaves pelvis at inferior part of the greater sciatic foramen (infrapiriform foramen) alongside the inf. gluteal vessels innervates the gluteus maximus m  Nerve to quadratus femoris m (L4, L5, S1) innervation of quadratus femoris muscle  Nerve to obturator internus m (L5, S1, S2) innervation of obturator internus muscle  Coccygeal Plexus Ventral rami of the S4, S5, and coccygeal spinal nn cutaneous innervation of coccygeal region Nerves a lot!