1. LUMBOSACRAL PLEXUS

2. Lumbosacral Plexus Components: Components: Lumbar plexus: L1--L4. Lumbosacral trunk: L4—L5. Sacral plexus: S1—S4.

3. Lumbar Plexus Formed in psoas major: Formed in psoas major: From ventral rami of L1..L4. Branches emerge from both lateral and medial sides of psoas major: Connect to sympathetic trunk.

4. Lumbar Plexus L1: L1: Variably connected to T12 (subcostal) and L2. Two branches emerge from lateral side of psoas major: Iliohypogastric (GSA): to side of buttock and pubis. Ilioinguinal (GSA): to anterior thigh, scrotum, labia majora.

5. Lumbar Plexus Genitofemoral nerve: Genitofemoral nerve: Emerges on anterior surface of psoas major. Genital branch: Enters inguinal canal. Supplies scrotum and labia majora (GSA). Supplies cremaster muscle (GSE). Femoral branch: Enters femoral sheath. Supplies skin over femoral triangle.

7. Lumbar Plexus Femoral nerve: Femoral nerve:L2—L4. Largest branch of lumbar plexus. Emerges from lateral side of psoas major.

8. Lumbar Plexus Femoral nerve: Femoral nerve: Enters thigh behind inguinal ligament. Supplies: In iliac fossa: Iliacus (GSE); pectineus (GSE); femoral artery (GVE).

9. Lumbar Plexus Femoral nerve: Femoral nerve:Supplies:Distally: Sartorius; quadriceps femoris; anterior thigh (GSA). Terminates as: Saphenous nerve (GSA) to medial thigh and foot.

10. Lumbar Plexus Obturator nerve: Obturator nerve:L2..L4. Emerges from medial side of psoas major. Descends along lateral wall of pelvis.

11. Lumbar Plexus Obturator nerve: Obturator nerve: Enters thigh through obturator foramen: In obturator groove it divides into: Anterior branch (anterior to adductor brevis). Posterior branch (posterior to adductor brevis).

12. Lumbar Plexus Obturator nerve: Obturator nerve:Supplies: Medial thigh muscles (GSE). Skin on medial thigh (GSA).

13. Sacral Plexus Superior gluteal nerve: Superior gluteal nerve:L4..S1. Passes through greater sciatic notch above piriformis. Supplies lateral gluteal compartment.

14. Sacral Plexus Inferior gluteal nerve: Inferior gluteal nerve:L5..S2. Passes through greater sciatic notch below piriformis. Supplies posterior gluteal compartment.

16. Sacral Plexus Posterior femoral cutaneous: Posterior femoral cutaneous: Runs with gluteal nerves deep to gluteus maximus. Then runs with sciatic nerve and gluteal artery.

17. Sacral Plexus Posterior femoral cutaneous: Posterior femoral cutaneous:Supplies: Skin on buttock (GSA) via inferior cluneal nerve. Skin of external genitalia (GSA) via perineal branches. Skin on back of thigh.

18. Sacral Plexus Nerves to lateral thigh compartment: Nerves to lateral thigh compartment: To inferior gemellus (GSE): L4..S1. To quadratus femoris (GSE): L4..S1. To piriformis (GSE): S1..S2.

19. Sacral Plexus Sciatic nerve: Sciatic nerve: Fusion of: Common peroneal (fibular). Tibial. Largest physical nerve in the body.

20. Sacral Plexus Sciatic nerve: Sciatic nerve: Exits pelvis through greater sciatic foramen: Inferior to piriformis (usually). Descends between gluteus maximus. Between greater trochanter and ischial tuberosity. Lies on: Ischium, gemelli, obturator internus, quadratus femoris.

21. Nerve Injuries Peripheral: Peripheral: All motor function and sensation supplied by nerve distal to injury is lost. Total muscle function is lost. Sensation over more than one dermatome is lost.

22. Nerve Injuries Nerve root: Nerve root: Usually affected by disc herniation immediately cranial (superior) to it. Sensory impairment over one dermatome. Muscle weakening. May only affect one root or the other.