LS plexus Flashcards
roots of the LS plexus
L1-S4
innervate the anterior compartment of the thigh
Femoral nerve
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.
Obturator
Exits the pelvis anterior and inferior to the piriformis via the greater sciatic foramen and then descends posterior to the femur.
Sciatic Nerve
At the inferior femur, the sciatic nerve divides into:
- The tibial nerve, which continues down the posterior tibia to innervate the posterior leg and plantar foot.
- The peroneal nerve, which wraps around the fibular neck and innervates the anterior and lateral leg and dorsal foot.
sciatic nerve is derived from
L4-S3
femoral and obturator nerves are derived from
L2 - L4
innervates the
quadriceps femoris muscles:
rectus femoris and the
vastus muscles: vastus medialis, vastus intermedius, and vastus lateralis.
Femoral nerve
innervates the adductor muscles, which are adductor longus, adductor brevis, and adductor magnus
Obturator nerve
innervates the hamstrings muscles, which are semimembranosus, semitendinosus, and the short and long heads of the biceps femoris muscle
Sciatic nerve
T/F
The tibial division of the sciatic nerve innervated the long and short heads of the biceps femoris.
False
long head only
short head is innervated by the peroneal division
Innervates gluteus maximus - which provides provides hip extension
Inferior gluteal nerve
L5-S2
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.
Superior Gluteal Nerve
L4-S1
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.
Genitofemoral
L1-L2
Provides sensory coverage to the lateral thigh.
Lateral cutaneous nerve of the thigh
Lateral Femoral Cutaneous nerve
L2-L3
Provides sensory coverage to the midline back of the thigh
Posterior cutaneous nerve of the thigh
Posterior Femoral Cutaneous nerve
S1-S3
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.
Pudendal nerve
S4 + S2 and S3
Common Peroneal Nerve
Deep peroneal nerve
Superficial peroneal nerve
compression site for the peroneal nerve
fibular neck
compression site for sural nerve
lateral malleolus
compression site for tibial nerve
tarsal tunnel
popliteal fossa
innervation of Tibialis anterior
deep peroneal nerve
L4-L5
action of tibialis anterior
Provides foot dorsiflexion and to a lesser extent foot inversion.
innervation of Extensor digitorum longus, extensor hallucis longus, and peroneus tertius
deep peroneal nerve
L5-S1
Actions of
Extensor digitorum longus
extensor hallucis longus,
peroneus tertius
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.
innervates Peroneus longus and peroneus brevis
Superficial peroneal nerve
L5-S1
Action of Peroneus longus and peroneus brevis
Provide foot eversion and to a lesser extent foot plantar flexion
innervates
The short extensor muscles of the foot: extensor digitorum brevis and extensor hallucis brevis
Deep peroneal nerve
L5-S1
Actions of the extensor digitorum brevis
extensor hallucis brevis
Extensor digitorum brevis extends the middle three toes.
Extensor hallucis brevis extends only the great toe and only at the proximal phalanx.
innervates gastrocnemius and soleus
superficial tibial nerve
S1 - S2
Actions of gastrocnemius and soleus
Both muscles provide foot plantar flexion: we test gastrocnemius with the knee extended and soleus with the knee flexed.
innervates tibialis posterior and flexor digitorum longus and flexor hallucis longus
deep tibial nerve
L5-S1
Actions
Tibialis posterior
Flexor digitorum longus
Flexor hallucis longus
Tibialis posterior provides foot inversion.
Flexor digitorum longus flexes the toes (except the great toe).
Flexor hallucis longus flexes the great toe.
