Sciatic Nerve Flashcards
What shape is the sciatic nerve?
A thick, flat band, approx 2cm wide
What are the nerve roots of the sciatic nerve?
L4-S3
What are the motor functions of the sciatic nerve?
Innervates the muscles of the posterior thigh and the hamstring portion of the adductor magnus Indirectly innervates (via its terminal branches) the muscles of the leg and foot
What are the sensory functions of the sciatic nerve?
No direct sensory functions Indirectly innervates (via its terminal branches) the skin of the lateral leg, heel, and both of the dorsal and plantar surfaces of the foot
What is the sciatic nerve derived from?
The lumbosacral plexus
What anatomical course does the sciatic nerve take?
After its formation, it leaves the pelvis and enters the gluteal region via the greater sciatic foramen
It emerges inferiorly to the piriformis muscle and descends in an inferolateral direction
As the nerve moves through the gluteal region, it crosses the posterior surface of the superior gemellus, obturator internus, inferior gemellus and quadratus femoris muscles
It then enters the posterior thigh by passing deep to the long head of the biceps femoris
What happens to the sciatic nerve in the posterior thigh?
It gives rise to branches to the hamstring muscles and adductor magnus
When does the sciatic nerve terminate?
When it reaches the apex of the popliteal fossa
How does the sciatic nerve terminate?
By bifurcating into the tibial and common fibular nerves
What can the sciatic nerve be described as?
Two individual nerves bundled together in the same connective sheath- the tibial and common fibular nerve
When do the tibial and common fibular nerves separate?
Usually at the apex of the popliteal fossa
In approx 12% of people, separate as they leave the pelvis
When must the anatomical course of the sciatic nerve be considered?
When administering intramuscular injections into the gluteal regions
How can the gluteal region be divided?
Into quadrants, using two lines, marked by bony landmarks-
One line descends vertically from the highest point on the iliac crest
The other horizontal line passes through the vertical line half way between the highest point on the iliac crest and ischial tuberosity
Regarding quadrants, where does the sciatic nerve pass?
Through the lower medial quadrant
What must be done to avoid damaging the sciatic nerve?
Intramuscular injections are given only in the upper lateral quadrant of the gluteal region
What muscles does the sciatic nerve directly innervate?
The muscles in the posterior compartment of the thigh, and the hamstring portion of the adductor magnus
How does the sciatic nerve indirectly innervate other muscles?
Via its two terminal branches, the tibial nerve and the common fibular nerve
What muscles does the tibial nerve innervate?
The muscles of the posterior leg (calf muscles), some of the intrinsic muscles of the foot
What muscles does the common fibular nerve innervate?
The muscles of the anterior leg, lateral leg, and the remain intrinsic foot muscles
In total, how much of the lower limb does the sciatic nerve innervate?
Muscles of the posterior thigh, entire leg and entire foot
Does the sciatic nerve have any direct cutaneous function?
No
How does the sciatic nerve provide indirect sensory innervation?
Via its terminal branches, the tibial nerve and common fibular nerve
What does the tibial nerve innervate?
The posterolateral and anterolateral sides of the leg
The plantar surface of the foot
What does the common fibular nerve innervate?
The lateral leg and dorsal surface of foot
