Anatomy - sacral plexus

Question 1

Where do the nerves forming the sacral plexus converge?

Answer 1

They converge towards the greater sciatic foramen

Question 2

What components contribute to make the sacral plexus?

Answer 2

1. The lumbosacral trunk (L4,5) from the lumbar plexus

2. S1-S5

Question 3

What does the sacral plexus lie on?

Answer 3

On the posterior pelvis

Question 4

What does the sacral plexus lie between?

Answer 4

Between piriformis and the pelvic fascia

Question 5

What does the sacral plexus lie behind?

Answer 5

Behind the internal iliac artery and vein

Question 6

Where do the superior gluteal artery and vein run relative to the sacral plexus?

Answer 6

Between the lumbosacral trunk and S1

Question 7

What runs between the second and third sacral nerves?

Answer 7

The inferior gluteal artery and vein

Question 8

What are the four major groups/areas supplied by the sacral plexus?

Answer 8

1. Supply to levator ani
2. Major muscular supply
3. Minor muscular supply
4. Sensory supply

Question 9

What are the four branches of the sacral plexus that supply levator ani?

Answer 9

1. Pelvic splancnic nerves (PSNS S2-4)
2. Pudendal nerve (S2-4)
3. Muscular branch to levator ani (pelvic surface) S3,4 -> levators ani and ishiococcygeus
4. Perineal branch of S4 -> external sphnicter and puborectalis

Question 10

What branch does the pudendal nerve give off to levator ani, and specifically which part of levator ani does it supply?

Answer 10

The pudendal nerve gives off the inferior rectal nerve which supplies the external sphincter and puborectalis

Question 11

What are the major muscular supply branches of the sacral plexus?

Answer 11

1. Sciatic nerve -> tibial nerve part (anterior divisions of L4-S3) and common peroneal part (posterior divisions of L4-S2)
2. Superior and inferior gluteal nerves (L4, S1, L5-S2)

Question 12

What are the 3 branches of the minor muscular supply from the sacral plexus?

Answer 12

Most enter the buttock inferior to piriformis muscle

1. Nerve to quadratus femoris (L4-S1)
2. Nerve to Piriformis (S1, S2)
3. Nerve to Obturator internus (L5-S2)

Question 13

What are the branches of the sensory supply arising from the sacral plexus?

Answer 13

1. Coccygeal nerve/coccygeal plexus

2. Posterior femoral cutaneous nerve (S1-3)