Sacral plexus

Question 1

where is the sacral plexus located

Answer 1

on the surface of the posterior pelvic wall, anterior to the piriformis muscle.

Question 2

The sacral plexus is formed by the

Answer 2

anterior rami (divisions) of the sacral spinal nerves S1, S2, S3 and S4.

It also receives contributions from the lumbar spinal nerves L4 and L5.

Question 3

At each vertebral level (S1-S4)….

Answer 3

paired spinal nerves leave the spinal cord via the intervertebral foramina of the vertebral column.

Question 4

The Branches

Answer 4

The anterior rami of the S1-S4 spinal roots (and the lumbosacral trunk) divide into several cords. These cords then combine together to form the five major peripheral nerves of the sacral plexus.

Question 5

name the 5 major peripheral nerves of the sacral plexus

Answer 5

superior gluteal nerve

inferior gluteal nerve

sciatic nerve and its divisions

posterior femoral cutaenous nerve

pudendal nerve

Question 6

as the nerves descend down the posteiro pelvic wall, they have 2 main destination:

Answer 6

1. Leave the pelvis via the greater sciatic foramen – these nerves enter the gluteal region of the lower limb, innervating the structures there.
2. Remain in the pelvis – these nerves innervate the pelvic muscles, organs and perineum.

Question 7

superior gluteal nerve

Answer 7

The superior gluteal nerve leaves the pelvis via the greater sciatic foramen, entering the gluteal region superiorly to the piriformis muscle. It is accompanied by the superior gluteal artery and vein for much of its course.

Question 8

roots of the superior gluteal nerve

Answer 8

L4, L5, S1

Question 9

motor function of the superior gluteal nerve

Answer 9

Innervates the gluteus minimus, gluteus medius and tensor fascia lata.

Question 10

sensory function of the superior gluteal nerve

Answer 10

none

Question 11

Inferior Gluteal Nerve

Answer 11

The inferior gluteal nerve leaves the pelvis via the greater sciatic foramen, entering the gluteal region inferiorly to the piriformis muscle.

It is accompanied by the inferior gluteal artery and vein for much of its course.

Question 12

roots of the inferior gluteal nerve

Answer 12

L5, S1, S2

Question 13

Motor function of the inferior gluteal nerve

Answer 13

innervates gluteus maximus

Question 14

Sensory function of the inferior gluteal nerve

Answer 14

none

Question 15

roots of the sciatic nerve

Answer 15

L4, L5, S1, S2, S3

Question 16

motor function of the sciatic nerve

Answer 16

Tibial portion – Innervates the muscles in the posterior compartment of the thigh (apart from the short head of the biceps femoris), and the hamstring component of adductor magnus. Innervates all the muscles in the posterior compartment of the leg and sole of the foot.

Common fibular portion – Short head of biceps femoris, all muscles in the anterior and lateral compartments of the leg and extensor digitorum brevis.

Question 17

sensory function of the sciatic nerve

Answer 17

Tibial portion: supplies the skin of the posterolateral leg, lateral foot and the sole of the foot.

Common fibular portion: supplies the skin of the lateral leg and the dorsum of the foot.

Question 18

Posterior Femoral Cutaneous

Answer 18

The posterior cutaneous nerve of thigh leaves the pelvis via the greater sciatic foramen, entering the gluteal region inferiorly to the piriformis muscle. It descends deep to the gluteus maximus and runs down the back of the thigh to the knee.

Question 19

roots of the posterior femoral cutaneous

Answer 19

S1, S2, S3

Question 20

Motor fucntion of the posterior femoral cutaenous

Answer 20

none

Question 21

Sensory fucntion of the posterior femoral cutaneous

Answer 21

Innervates the skin on the posterior surface of the thigh and leg. Also innervates the skin of the perineum.

Question 22

pudendal nerve

Answer 22

This nerve leaves the pelvis via the greater sciatic foramen, then re-enters via the lesser sciatic foramen. It moves anterosuperiorly along the lateral wall of the ischiorectal fossa, and terminates by dividing into several branches.

Question 23

roots of the pudendal nerve

Answer 23

S2, S3, S4

Question 24

Motor function of the pudendal nerve

Answer 24

Innervates the skeletal muscles in the perineum, the external urethral sphincter, the external anal sphincter, levator ani.

Question 25

sensory function of the pudendal nerve

Answer 25

innervates the penis and clitoris and most of the skin of the perineum

Question 26

Other Branches

Answer 26

In addition to the five major nerves of the sacral plexus, there are a number of smaller branches. These tend to be nerves that directly supplying muscles (with the exception of the perforating cutaneous nerve, which supplies the skin over the inferior gluteal region and the pelvic splanchnic nerves, which innervate the abdominal viscera):

Nerve to piriformis

Nerve to obturator internus

Nerve to quadratus femoris

Question 27

way to remeber roots fo the pudendal

Answer 27

S2, S3, S4 keeps poo off the floor!!!!!!!!!!!!!! :)

Question 28

acronymn for the sacral plexus peripheral nerves

Answer 28

Salmon is so perfectly pink

This stands for Superior Gluteal, Inferior Gluteal, Sciatic, Posteriorcutaneous nerve of thigh, Pudendal.