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Flashcards in Sciatic nerve Deck (16):

What are the nerve roots, motor and sensory function of the sciatic nerve?

Roots: L4-S3
Motor: innervates muscles of posterior thigh & hamstring of adductor magnus, terminal branch innervates muscles of leg & foot
Sensory: indirectly innervate (terminal branches) skin of lateral leg, heel, dorsal & plantar surfaces of foot


What are the significance of the sciatic nerve?

the largest nerve of the body
major nerve of lower limb
thick flat band - 2cm


What is the sciatic nerve derived from and name the beginning of it's anatomical course

from lumbosacral plexus
leaves pelvis to enter gluteal region via sciatic foramen
travels down thigh inferior to piriformis muscle, inferolaterally


Describe the anatomical course of the sciatic nerve from the gluteal region to the thigh

after passing posterior to gluteus minimis and piriformis, the sciatic nerve then crosses the posterior surface of the superior gemellus, obturatus externus, inferior gemellus, obturator internus, quadratus femoris (all deep muscles of gluteal region), entering posterior thigh by passing deep to long head of biceps femoris


What happens once the nerve is in the posterior thigh?

gives rise to nerve branches innervating the hamstring muscles and part of the adductor magnus
when nerve enters popliteal region, it bifurcates into the tibial and common fibular nerves


describe the sciatic nerve

2 individual nerve bundles (common fibular & tibial)
normally separated at apex of popliteal fossa
can separate as they leave the pelvis in some people


Intramuscular injections

careful to avoid the sciatic nerve - split gluteal region into 4 sections by 2 lines
vertical line: from highest point of iliac crest
horizontal: passes vertical line halfway between highest point of iliac crest and ischial tuberosity (sitting bones)
inject through the upper lateral quadrant as the sciatic nerve runs through the lower medial quadrant


motor functions of sciatic nerve

muscles of posterior thigh, hamstring of adductor magnus


What are the 2 terminal branches of the sciatic nerve?

common fibular


what are the motor functions of tibial nerve?

muscles of the posterior leg (calf muscles)
some intrinsic muscles of the leg


What are the motor functions of the common fibular nerve?

muscles of anterior and lateral leg
remaining instrinsic foot muscles not innervated by the tibial muscle


including the terminal branches (tibial & common fibular nerve) which areas of the lower limb is the sciatic nerve responsible for motor functions of?

posterior thigh, entire leg & entire foot


does the sciatic nerve have any sensory functions?

not directly, but indirectly through the common fibular and tibial nerves


sensory innervation of the tibial nerve

postero-lateral & antero-lateral sides of the leg, plantar surface of foot (sole)


sensory function of common fibular nerve

lateral leg & dorsal foot (top of foot)


What are the 4 sciatic nerve branches responsible for sensory?

1. sural nerve (branches of common fibular & tibial postero-lateral)
2. deep fibular nerve (branch of common fibular for proximal lateral leg)
3. superficial fibular nerve (branch of common fibular for lower lateral leg)
4. medial calcaneal branches (branches of tibial for plantar foot)