Week 9 - The Sciatic Nerve

Question 1

What are the motor functions of the sciatic nerve?

Answer 1

• Innervates the posterior thigh muscles
• Innervates the hamstring portion of adductor magnus via the tibial nerve, which branches off from it.
• Indirectly innervates muscles in leg and foot via terminal branches

Question 2

Does the sciatic nerve directly provide sensory innervation to any regions?

Answer 2

No

Question 3

What are the sensory functions of the sciatic nerve?

Answer 3

No direct functions, but indirectly innervates the following regions via terminal branches:

• Skin of dorsal/plantar surfaces of foot
• Skin of heel
• Skin of lateral leg

Question 4

From what is the sciatic nerve derived?

Answer 4

The lumbrosacral plexus

Question 5

Through which anatomical feature does the sciatic nerve leave the pelvis?

Answer 5

The greater sciatic foramen

Question 6

Which area does the sciatic nerve enter having left the pelvis via the greater sciatic foramen?

Answer 6

The gluteal region

Question 7

Which muscle does the sciatic nerve enter the gluteal region inferiorly to?

Answer 7

Piriformis

Question 8

Describe how the sciatic nerve descends through the gluteal region in relation to the muscles.

Answer 8

Between superficial and deep groups -

posteriorly to superficial, but anteriorly to deep

Question 9

What branches arise from the sciatic nerve as it descends the posterior thigh?

Answer 9

Motor branches to the hamstrings

Question 10

Where does the sciatic nerve terminate, and how?

Answer 10

At the apex of the popliteal fossa - bifurcates into the tibial and common fibular nerves.

Question 11

Is the sciatic nerve a single nerve?

Answer 11

No - tibial and common fibular nerves bundled together into one sheath..

Question 12

The gluteal region can be divided into quadrants. Where would the vertical line descend down from?

Answer 12

The highest point on the iliac crest

Question 13

The gluteal region can be divided into quadrants. Between which landmarks would you draw the horizontal line?

Answer 13

Half way between the highest point of the iliac crest and the ischial tuberosity

Question 14

Through which quadrant of the gluteal region does the sciatic nerve pass?

Answer 14

The lower medial quadrant

Question 15

Into which quadrant of the gluteal region is an intramuscular injection given?

Answer 15

The upper lateral quadrant

Question 16

What are the nerve roots of the sciatic nerve?

Answer 16

L4, L5, S1, S2, S3