LS plexus

Question 1

roots of the LS plexus

Answer 1

L1-S4

Question 2

innervate the anterior compartment of the thigh

Answer 2

Femoral nerve

Question 3

Descends medial to the femoral nerve, anterior to the sacrospinous ligament and exits via the obturator canal, down the medial aspect of the thigh to innervate the medial compartment muscles.

Answer 3

Obturator

Question 4

Exits the pelvis anterior and inferior to the piriformis via the greater sciatic foramen and then descends posterior to the femur.

Answer 4

Sciatic Nerve

Question 5

At the inferior femur, the sciatic nerve divides into:

Answer 5

1. The tibial nerve, which continues down the posterior tibia to innervate the posterior leg and plantar foot.
2. The peroneal nerve, which wraps around the fibular neck and innervates the anterior and lateral leg and dorsal foot.

Question 6

sciatic nerve is derived from

Answer 6

L4-S3

Question 7

femoral and obturator nerves are derived from

Answer 7

L2 - L4

Question 8

innervates the
quadriceps femoris muscles:
rectus femoris and the
vastus muscles: vastus medialis, vastus intermedius, and vastus lateralis.

Answer 8

Femoral nerve

Question 9

innervates the adductor muscles, which are adductor longus, adductor brevis, and adductor magnus

Answer 9

Obturator nerve

Question 10

innervates the hamstrings muscles, which are semimembranosus, semitendinosus, and the short and long heads of the biceps femoris muscle

Answer 10

Sciatic nerve

Question 11

T/F

The tibial division of the sciatic nerve innervated the long and short heads of the biceps femoris.

Answer 11

False

long head only

short head is innervated by the peroneal division

Question 12

Innervates gluteus maximus - which provides provides hip extension

Answer 12

Inferior gluteal nerve

L5-S2

Question 13

innervates gluteus medius, gluteus minimus, and tensor fasciae latae; all of which provide hip abduction –tensor fasciae latae does when the hip is in flexion.

Answer 13

Superior Gluteal Nerve

L4-S1

Question 14

Genital branch innervates the cremaster muscle.
Provides sensory coverage to the scrotum or labia.
Femoral branch is purely sensory.
Provides sensory coverage to the femoral triangle.

Answer 14

Genitofemoral

L1-L2

Question 15

Provides sensory coverage to the lateral thigh.

Answer 15

Lateral cutaneous nerve of the thigh
Lateral Femoral Cutaneous nerve
L2-L3

Question 16

Provides sensory coverage to the midline back of the thigh

Answer 16

Posterior cutaneous nerve of the thigh
Posterior Femoral Cutaneous nerve
S1-S3

Question 17

Branches into the inferior rectal nerve, perineal nerve, and dorsal nerve to the penis or clitoris.
Provides motor innervation to the external urethral and anal sphincters and external genitalia and it provides sensory coverage to the anus and external genitalia.

Answer 17

Pudendal nerve

S4 + S2 and S3

Question 18

Common Peroneal Nerve

Answer 18

Deep peroneal nerve

Superficial peroneal nerve

Question 19

compression site for the peroneal nerve

Answer 19

fibular neck

Question 20

compression site for sural nerve

Answer 20

lateral malleolus

Question 21

compression site for tibial nerve

Answer 21

tarsal tunnel

popliteal fossa

Question 22

innervation of Tibialis anterior

Answer 22

deep peroneal nerve

L4-L5

Question 23

action of tibialis anterior

Answer 23

Provides foot dorsiflexion and to a lesser extent foot inversion.

Question 24

innervation of Extensor digitorum longus, extensor hallucis longus, and peroneus tertius

Answer 24

deep peroneal nerve

L5-S1

Question 25

Actions of
Extensor digitorum longus
extensor hallucis longus,
peroneus tertius

Answer 25

Extensor digitorum longus extends the toes (except the great toe)
Extensor hallucis longus extends the great toe, only
Peroneus tertius assists in foot eversion.

To a lesser extent, all three of these muscles also provide foot dorsiflexion.

Question 26

innervates Peroneus longus and peroneus brevis

Answer 26

Superficial peroneal nerve

L5-S1

Question 27

Action of Peroneus longus and peroneus brevis

Answer 27

Provide foot eversion and to a lesser extent foot plantar flexion

Question 28

innervates

The short extensor muscles of the foot: extensor digitorum brevis and extensor hallucis brevis

Answer 28

Deep peroneal nerve

L5-S1

Question 29

Actions of the extensor digitorum brevis

extensor hallucis brevis

Answer 29

Extensor digitorum brevis extends the middle three toes.

Extensor hallucis brevis extends only the great toe and only at the proximal phalanx.

Question 30

innervates gastrocnemius and soleus

Answer 30

superficial tibial nerve

S1 - S2

Question 31

Actions of gastrocnemius and soleus

Answer 31

Both muscles provide foot plantar flexion: we test gastrocnemius with the knee extended and soleus with the knee flexed.

Question 32

innervates tibialis posterior and flexor digitorum longus and flexor hallucis longus

Answer 32

deep tibial nerve

L5-S1

Question 33

Actions
Tibialis posterior
Flexor digitorum longus
Flexor hallucis longus

Answer 33

Tibialis posterior provides foot inversion.
Flexor digitorum longus flexes the toes (except the great toe).
Flexor hallucis longus flexes the great toe.