The Sciatic Nerve

Question 1

State the nerve roots of the sciatic nerve.

Answer 1

L4-S3

Question 2

Outline the course of the sciatic nerve.

Answer 2

• Derived from the lumbosacral plexus
• After its formation, it leaves the pelvis and enters the gluteal region via the greater sciatic foramen
• 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
• Enters the posterior thigh by passing deep to the long head of the biceps femoris
• Within the posterior thigh, the nerve gives rise to branches to the hamstring muscles and adductor magnus

Question 3

Where does the sciatic nerve terminate?

Answer 3

Apex of the popliteal fossa

• here, it bifurcates into the tibial and common fibular nerves

Question 4

State briefly which muscles the tibial nerve innervates.

Answer 4

1. Muscles of the posterior leg - calf muscles

2. Some intrinsic foot muscles

Question 5

State briefly which muscles the common fibular nerve innervates.

Answer 5

1. Muscles of the anterior leg
2. Muscles of the lateral leg
3. Remaining intrinsic foot muscles (other than the ones tibial nerve innervates)