Sacral Plexus

Question 1

What is the sacral plexus?

Answer 1

A network of nerve fibres that supplies the skin and muscles of the pelvis and lower limb

Question 2

Where is the sacral plexus located?

Answer 2

On the surface of the posterior pelvic wall, anterior to the piriformis muscle

Question 3

What is the sacral plexus formed by?

Answer 3

The anterior rami (divisons) of the sacral spinal nerves S1, S2, S3, and S4.
It also receives contributions from the lumbar spinal nerves L4 and L5

Question 4

Where does the sacral plexus begin?

Answer 4

As the anterior fibres of S1, S2, S3, and S4

Question 5

What forms the lumbosacral trunk?

Answer 5

The 4th and 5th lumbar roots

Question 6

What happens to the lumbosacral trunk?

Answer 6

It descends into the pelvis, to meet the sacral roots as they emerge from the spinal cord

Question 7

What happens to the anterior rami of the S1-S4 spinal roots and the lumbosacral trunk?

Answer 7

They divide into several cords, which then combine together to form the five major peripheral nerves of the sacral plexus

Question 8

Where do the give major peripheral nerves of the sacral plexus travel?

Answer 8

They descent down the posterior pelvic wall, and then either-
Leave the pelvis via the greater sciatic foramen
Remain in the pelvis

Question 9

What happens to the nerves that leave the pelvis via the greater sciatic foramen?

Answer 9

They enter the gluteal region of the lower limb, innervating the structures there

Question 10

What happens to the nerves that remain in the pelvis?

Answer 10

They innervate the pelvic muscles, organs and perineum

Question 11

What are the five major peripheral nerves of the brachial plexus?

Answer 11

Superior gluteal nerve
 Inferior gluteal nerve
 Sciatic nerve
 Posterior femoral cutaneous
 Pudendal

Question 12

What course does the superior gluteal nerve take?

Answer 12

It leaves the pelvis via the greater sciatic foramen, entering the gluteal region superiorly to the piriformis muscle

Question 13

What is the superior gluteal muscle accompanied by for much of its course?

Answer 13

The superior gluteal artery and vein

Question 14

What are the roots of the superior gluteal nerve?

Answer 14

L4, L5, S1

Question 15

What muscles does the superior gluteal nerve innervate?

Answer 15

Gluteus minimis
Gluteus medius
Tensor fascia latae

Question 16

What are the sensory functions of the superior gluteal nerve?

Answer 16

None

Question 17

What course does the inferior gluteal nerve take?

Answer 17

It leaves the pelvis via the greaer sciatic foramen, entering the gluteal region inferiorly to the piriformis muscle

Question 18

What is the inferior gluteal nerve accompanied by for much of its course?

Answer 18

The inferior gluteal artery and vein

Question 19

What are the roots of the inferior gluteal nerve?

Answer 19

L5, S1, S2

Question 20

What muscle does the inferior gluteal nerve innervate?

Answer 20

Gluteus maximus

Question 21

What is the sensory function of the inferior gluteal nerve?

Answer 21

None

Question 22

What are the roots of the sciatic nerve?

Answer 22

L4, L5, S1, S2, S3

Question 23

What are the parts of the sciatic nerve?

Answer 23

Tibial portion

Common fibular portion

Question 24

What muscles does the tibial portion of the sciatic nerve innervate?

Answer 24

All muscles of posterior compartment of thigh, including the hamstring portion of the adductor magnus, apart from the short head of the biceps femoris
All muscles in the posterior compartment of the leg
All muscles in sole of foot

Question 25

What muscles does the common fibular portion of the sciatic nerve innervate?

Answer 25

Short head of biceps femoris
All muscles of anterior and lateral compartments of the leg
Extensor digitorum brevis

Question 26

What are the sensory functions of the tibial portion of the sciatic nerve?

Answer 26

Innervates the skin on the posterolateral and medial surfaces of the foot, as well as the sole of the foot

Question 27

What are the sensory functions of the common fibular portion of the sciatic nerve?

Answer 27

Innervates the skin on the anterolateral surface of the leg and the dorsal aspect of the foot

Question 28

What course does the posterior femoral cutaneous nerve take?

Answer 28

It 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 29

What are the roots of the posterior femoral cutaneous nerve?

Answer 29

S1, S2, S3

Question 30

What muscles does the posterior femoral cutaneous nerve innervate?

Answer 30

None

Question 31

What is the sensory function of the posterior femoral cutaneous?

Answer 31

Innervates the skin on the posterior surface of the thigh and leg
Innervates skin of perineum

Question 32

What course does the pudendal nerve take?

Answer 32

The 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

Question 33

How does the pudendal nerve terminate?

Answer 33

By dividing into several branches

Question 34

What are the roots of the pudendal nerve?

Answer 34

S2, S3, S4

Question 35

What are the motor functions of the pudendal nerve?

Answer 35

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

Question 36

What is the sensory function of the pudendal nerve?

Answer 36

Innervates the penis and clitoris, and most of the skin of the perineum

Question 37

What is found in addition to the five major nerves of the sacral plexus?

Answer 37

A number of smaller branches

Question 38

What do the smaller branches coming from the sacral plexus tend to be?

Answer 38

Nerves that directly supply muscles

Question 39

What is the exception to the smaller branches of the sacral plexus directly supplying muscles?

Answer 39

The perforating cutaneous nerve, which supplies the skin over the inferior gluteal region
The pelvic splanchnic nerves, which innervate the abdominal viscera

Question 40

What are the important smaller branches of the sacral plexus?

Answer 40

Nerve to piriform
Nerve to obturator internus
Nerve to quadrator femoris