Sacral Plexus

Question 1

What is it?

Answer 1

Network of nerve fibres that supplies the skin and musculature of the pelvis and lower limb

Question 2

Location

Answer 2

Surface of the posterior pelvic wall, anterior to the piriformis muscle

Question 3

What forms it?

Answer 3

Anterior rami of sacral spinal nerves S1-S4

Also receives contributions from L4 and L5

Question 4

Branches

Answer 4

Superior gluteal nerve 
Inferior gluteal nerve 
Sciatic nerve
Posterior femoral cutaneous 
Pudendal nerve 
(Some Irish Sailor Pesters Polly) 
Nerve to piriformis 
Nerve to obturator internus 
Nerve to quatrator femoris

Question 5

Superior gluteal nerve

Answer 5

• Roots - L4, L5, S1
• Motor functions - innervates gluteus minimus, gluteus medium and tensor fascia latae
• Sensory functions - none

Question 6

Inferior gluteal nerve

Answer 6

• Roots - L5, S1, S2
• Motor functions - innervates gluteus maximus
• Sensory functions - none

Question 7

Sciatic nerve

Answer 7

• Roots - L4, L5, S1, S2, S3
• Motor function - tibial portion - innervates all muscles in posterior thigh including hamstring portion of adductor magnus (not short head of biceps femoris), all muscles in posterior leg and sole of foot // common fibular portion - short head of biceps femoris, all muscles in anterior and lateral leg and extensor digitorum braves
• Sensory functions - tibial - skin on posterolateral and medial surface of the foot + sole of foot // common fibular - skin on anterolateral surface of leg and dorsal aspect of foot

Question 8

Posterior femoral cutaneous nerve

Answer 8

• Roots - S1, S2, S3
• Motor function - none
• Sensory function - skin on the posterior surface of the thigh and leg, innervates skin on the perineum

Question 9

Pudendal nerve

Answer 9

• Roots - S2, S3, S4
• Motor functions - skeletal muscles in the perineum, external urethral sphincter, external anal sphincter, levator ani
• Sensory function - penis and clitoris and most of the skin on the perineum