Sacral Plexus

Question 1

The sacral plexus lies on which muscle?

Answer 1

Posterior pelvic wall, anterior to the piriformis muscle

Question 2

What is the sacral plexus formed by?

Answer 2

The union of the ventral rami of spinal nerves L4, L5 and S1 to S4

Question 3

The supply from the lumbar ventral rami comes from what?

Answer 3

Lumbosacral trunk

Question 4

The sarcal plexus supplies what?

Answer 4

The posterior aspect of the lower limb plus the perineum

Question 5

What are the two main branches of the sacral plexus?

Answer 5

Main branch to lower limb - sciatic nerve

Main branch to perineum - pudneal nerve

Question 6

The superior and the inferior gluteal nerves are what?

Answer 6

Small motor branches of the sacral plexus

Question 7

What are the root value of the superior gluteal nerve?

Answer 7

L4-S1

Question 8

What are the root values of the inferior gluteal nerve?

Answer 8

Root value of L5-S2

Question 9

List the muscles supplied by the superior gluteal nerve below:

Answer 9

1. Gluteus medius muscle
2. Gluteus minimus muscle
3. Tensor fascia late

And the priformis muscle

Question 10

The inferior gluteal nerve supplies only one muscle in the gluteal region. Which is it?

Answer 10

Gluteus maximus

Question 11

Other branches of the sacral plexus which innervate muscles in the lower limb apart fron the gluteus maximus?

Answer 11

1. Nerve to piriformis
2. Posterior Cutaneous Nerve to the Thigh
3. Nerve to quadratus femoris
4. Nerve to obturator internus

Question 12

What is the sciatic nerve a continuation of and why is this special?

Answer 12

Largest nerve in the body and is the continuation of the main part of the sacral plexus.

Question 13

What are the root values of the sciatic nerve?

Answer 13

L4 to S3

Question 14

In the glutel region how does the sciatic nerve contribute?

Answer 14

Very little motor or sensory innervation, aside from branches to the posterior aspect of the hip joint.

Question 15

What does the sciatic nerve pass through?

Answer 15

It passes through the greater sciatic foramen, inferior to the piriformis muscle, passing behind the deep abductors of the hip joint between the ischial tuberosity and greater trochanter of the femur to enter the posterior compartment of the thigh

Question 16

What does the sciatic nerve divide at the popliteal fossa into?

Answer 16

1. Tibial nerve
2. Common fibular nerve

Question 17

Answer 17

Piriformis muscle

Question 18

What is sciatica?

Answer 18

As you get older the flexibility and elasticity of muscles, ligaments and joints diminish. Coupled with the forces that weight, gravity (plus 24 vertebrae, and a skull), place on the lower lumbar spine you can understand how vertebral foramen become narrowed and compress on the nerve roots.