Sacral plexus

Question 1

superior gluteal nerve

Answer 1

L4, L5, S1

Question 2

inferior gluteal nerve

Answer 2

L5, S1, S2

Question 3

posterior cutaneous nerve of the thigh

Answer 3

S1, S2 dorsal

S2, S3 ventral

Question 4

Sciatic nerve

Answer 4

L4, L5, S1, S2, S3

Question 5

tibial nerve

Answer 5

from sciatic nerve, anterior division, L4-S3

Question 6

fibular nerve

Answer 6

from sciatic nerve, posterior division, L4-S2

Question 7

Pudental nerve

Answer 7

S2, S3, S4

Question 8

What are the motor functions of the superior glutelal nerve? (leaves via greater sciatic foramen)

Answer 8

gluteus minimus
gluteus medius
tensor fascia latae

Question 9

What are the motor functions of the inferior glutelal nerve? (leaves via greater sciatic foramen)

Answer 9

gluteus maximus

Question 10

Do the superior and inferior gluteal nerves have sensory functions?

Answer 10

NO

Question 11

Where does the sciatic nerve split?

Answer 11

apex of popliteal fossa

Question 12

Clinical relevence of sciatic nerve

Answer 12

intramuscluar injections

pyriformis syndrome: can cause symptoms related to sciatic nerve

Question 13

motor function of tibial nerve (popliteal)

Answer 13

foot plantar flexion + inversion + toe flexion

Question 14

What is the end of the tibial nerve ?

Answer 14

at distal end of posterior surface of tibia: division into medial + lateral plantar nerves

Question 15

What is the sural nerve ?

Answer 15

cutaneous nerve, provides sensation to posterior lateral distal thrid of the tibia

Question 16

What are tibial nerve lesions common?

Answer 16

vulnerable to direct injury in popliteal fossa

can be entrapped under flexor retinaculum –> tarsal tunnel syndrome

Question 17

What is the trajectory of the posterior cutaneous nerve of the thigh?

Answer 17

exits via greater sciatic foramen, passes under gluteus maximus

Question 18

What is the specificity of the posterior cutaneous nerve of the thigh?

Answer 18

branches all cutaneous, distributed to gluts, perineum, flexor aspect of thigh + leg

Question 19

What is the trajectory of the sciatic nerve?

Answer 19

• 2 individual nerves bundled together in same CT sheath (tibial + common fibular nerves)usually separate at apex of popliteal fossa.
• nerve moves through gluteal region
  crosses posterior surface of superior gemellus, obturator internus, inferior gemellus, quadratus femoris muscle
  enters the posterior thigh by passing deep to long head of biceps femoris
  in posterior thigh nerve gives off branches to hamstring muscles + adductor magnus
  reaches apex of popliteal fossa
  terminates by bifurcating into tibial + common fibular nerves.

Question 20

What is the trajectory of the superior gluteal nerve?

Answer 20

• leaves pelvis via greater sciatic foramen, entering gluteal region superiorly to piriformis muscle
• accompanied by superior gluteal artery + vein for much of its course

Question 21

What is the trajectory of the inferior gluteal nerve?

Answer 21

-leaves pelvis via greater sciatic foramen
entering gluteal region inferiorly to piriformis muscle
-accompanied by inferior gluteal artery + vein for much of its course.

Question 22

What odes the sciatic nerve innervate?

Answer 22

passes through gluteal region but does not innervate any muscles there

Question 23

What is the trajectory of the surral nerve?

Answer 23

-descends between heads of gastrocnemius
pierces deep fascia proximally in leg
joined at variable level by sural communicating branch of common fibular nerve
descends lateral to calcaneal tendon, near short saphenous vein, to region between lateral malleolus + calcaneus
supplies posterior + lateral skin of distal third of leg
then passes distal to lateral malleolus along lateral side of foot + little toe, supplying overlying skin

Question 24

What is the trajectory of the tibial nerve?

Answer 24

-At level of knee tibial nerve becomes superficial to popliteal vessels + crosses to medial side of artery
In distal popliteal fossa: overlapped by junction of the 2 heads of gastrocnemius
travels through popliteal fossa, giving off branches to muscles in superficial posterior compartment of leg (gastrocnemius + soleus)
but in distal third: covered only by skin + fasciae, overlapped sometimes by flexor hallucis longus, lies on tibialis posterior for most of its course except distally, where it adjoins posterior surface of tibia
ends under retinaculum flexorum by dividing into medial + lateral plantar nerves

Question 25

What is the trajectory of the fibular nerve?

Answer 25

-descends obliquely along lateral side of popliteal fossa, close to medial margin of biceps femoris muscle lies between tendon of Biceps femoris + lateral head of Gastrocnemius muscle winds around neck of fibula, between Peronæus longus + bone.

Question 26

2 cutaneous branches arise directly from common fibular nerve as it moves over lateral head of gastrocnemius, what are they called?

Answer 26

o Sural communicating nerve | o Lateral sural cutaneous neve

Question 27

What does the sural communicating nerve innervate?

Answer 27

nerve combines with branch of tibial nerve to form sural nerve, innervates skin over lower posterolateral leg.

Question 28

What does the lateral surral cutaneous nerve innervate?

Answer 28

Innervates skin over upper lateral leg.

Question 29

- In addition to the nerves Sural communicating nerve and the Lateral sural cutaneous neve, terminal branches of common fibular nerve also have cutaneous function, what are they called?

Answer 29

o Superficial fibular nerve | o Deep fibular nerve

Question 30

What does the superficial fibular nerve innervate?

Answer 30

Innervates skin of anterolateral leg, dorsum of foot (except skin between first + second toes).

Question 31

What does the deep fibular nerve innervate?

Answer 31

Innervates skin between first + second toes.

Question 32

What are the 3 branches of the fibular nerve?

Answer 32

o COMMON FIBULAR o SUPERFICIAL BRANCH: o DEEP FIBULAR NERVE

Question 33

What are the motor functions of the common fibular branch of the fibular nerve?

Answer 33

 short head of biceps femoris muscle (part of hamstring muscles, which flex at knee).  provides SUPERFICIAL + DEEP BRANCHES.  If common fibular nerve damaged --> patient may lose ability to dorsiflex + evert foot +lose ability to extend digits

Question 34

What are the motor functions of the superficial branch of the fibular nerve?

Answer 34

 provides innervation to muscles of lateral compartment of leg; fibularis longus + brevis (act to evert foot)

Question 35

What are the motor functions of the deep fibular branch of the fibular nerve?

Answer 35

 innervates muscles of anterior compartment of leg (lateral to tibial crest); tibialis anterior, extensor digitorum longus, extensor hallucis longus --> act to dorsiflex foot + extend digits  also innervates some intrinsic muscles of foot  Entrapment of deep fibular nerve in inferior extensor retinaculum (ANTERIOR TARSAL SYNDROME)

Question 36

What is the pudental nerve?

Answer 36

- nerve of perineum + pelvic floor

Question 37

What is the trajectory of the pudental nerve?

Answer 37

- emerges from pelvis courses through gluteal region through greater sciatic foramen, below piriformis muscle then turns forward around sacrospinous ligament + leaves gluteal region through lesser sciatic foramen (between sacrotuberous + sacrospinous ligaments) occupies very constant position over ischial spine then directed into pudendal canal (lies on obturator fascia above falciform ridge on ischial tuberosity) in pudendal canal: nerve divides into: inferior rectal nerve, dorsal nerve of penis or clitoris, perineal nerve

Question 38

How can the pudental be blocked?

Answer 38

-may be ‘blocked’ by infiltration with local anaesthetic applied via needle passed through lateral wall of vagina to numb perineal + anal skin.

Question 39

How can the pudental nerve be palpated?

Answer 39

- may also be palpated over ischial spine through lateral wall of rectum + motor terminal latencies measured.