Lumbosacral Plexus

Question 1

Lumbar Plexus

Answer 1

From ventral rami of L₁-L₄

Innervates lower limb, some of abdomen and pelvis

Question 2

Areas Innervated and Result of Injury for Femoral Nerve

Answer 2

Largest Branch of the Lumbar Plexus

Supplies skin and anterior thigh muscles (thigh flexors & knee extensors – motor innervation to quadricep muscles & sartorius)

• Contains the saphenous nerve

Result of Injury: loses the ability to extend the knee

Question 3

Saphenous Nerve

Answer 3

Supplies sensory innervation to the medial aspect of the lower leg.

Question 4

Obturator Nerve

Answer 4

Innervates adductor muscles of thigh (adductor magnus, longus, brevis and gracilis)

Question 5

Why are the lumbar and sacral plexuses often grouped together as the lumbosacral plexus?

Answer 5

Because of the intermingling of fibers (carried by the lumbosacral trunk)

Question 6

What is the lumbosacral plexus?

Answer 6

Large nervous system structure that is formed from the ventral rami of spinal nerves L₁-S₄. These nerves supply the lower abdomen, pelvis, gluteal region and lower limbs.

Question 7

Sacral Plexus

Answer 7

From ventral rami of L₄-S₄

Question 8

Sciatic Nerve -

Areas it innervates & result of injury

Answer 8

Largest nerve of the Sacral Plexus

Two nerves wrapped in a common sheath

• Tibial & common fibural nerve

innervates hamstrings (thigh extensors & knee flexors) and part of adductor magnus

Sciatica = pain radiating down leg along branches of sciatic nerve as a result of herniated disc.

Transected sciatic nerve results in inability to flex foot & ankle movements are lost ►foot drops into plantar flexion (dangles)

Question 9

Tibial Nerve –

Location, areas innervated and result if injured

Answer 9

Bifurcates to form medial and lateral plantar nerves

• Branches off sciatic proximal to knee

Supplies skin & muscles of posterior calf and sole of foot

Result of injury: inability to support the weight of the body when stepping forward on the foot (weakness or loss of plantar flexion)

Question 10

Common Fibular Nerve

Location, Areas Innervated, Result of Injury

Answer 10

Branches further to form Superficial & Deep Fibular Nerves

• Branches off sciatic lateral to fibula

Deep fibular nerve: anterior & lateral lower leg (dorsiflexors & toe extensors)

Result if injured: weakness or loss of dorsiflexion of the foot and extension of the toes.

Superficial fibular nerve: lateral lower leg (foot eversion & plantar flexion)

Question 11

Pudendal Nerve

Answer 11

Supplies skin and muscles of perineum; external genitali & sphincter

(responsible for voluntary control of urination)