FUNCTIONAL COMPONENTS OF THE INNERVATION

FUNCTIONAL COMPONENTS OF THE INNERVATION

LUMBOSACRAL PLEXUS

Lumbosacral Plexus

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

Lumbar Plexus

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.

Sympathetic Trunks and Pathways

Lumbar Plexus
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.

Lumbar Plexus

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.

Lumbar Plexus

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

Lumbar Plexus

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

Lumbar Plexus

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

Lumbar Plexus

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

Lumbar Plexus

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).

Lumbar Plexus

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

Sacral Plexus

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

Sacral Plexus

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

Sacral Plexus

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

Sacral Plexus

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.



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

Sacral Plexus

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

Sacral Plexus

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.

Nerve Injuries

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.

Nerve Injuries

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.