lecture 48 LE nervous structures

lumbosacral plexus

what provides innervation to the lower extremity?

lumbar and sacral plexuses which are connected by the lumbosacral trunk

what is the lumbosacral plexus formed by?

ventral rami from L1-L4 spinal levels

what is the lumbar plexus formed by?

lumbar plexus

what plexus occurs within the psoas major m?

six

how many branches does the lumbar plexus have?

from lateral, anterior, and medial borders

how do the branches of the lumbar plexus emerge from the psoas major m?

T12, L1

what contribution(s) give rise to the iliohypogastric n?

L1

what contribution(s) give rise to the ilioinguinal n?

L2, L3

what contribution(s) give rise to the lateral femoral cutaneous n?

L2, 3, 4

what contribution(s) give rise to the femoral n?

plexus roots, divisions, branches

what are the components of the lumbar plexus in order?

iliohypogastric, ilioinguinal, lateral femoral cutaneous n, femoral n

what nn emerge from the lateral border of the psoas major m (lumbar plexus) from superior to inferior?

abdominal mm and the skin of the lower anterior abd wall

what does the iliohypogastric n supply?

skin of groin and scrotum or labia majora

the ilioinguinal n enters the inguinal canal and innervates what?

skin over lateral surface of thigh

what does the lateral femoral cutaneous n innervate?

behind inguinal ligament lateral to the femoral sheath

how does the femoral n enter the thigh?

anterior thigh mm

what does the femoral n supply?

genitofemoral n

what n emerges from the anterior surface of psoas major m (lumbar plexus)?

genital branch, femoral branch

what does the genitofemoral n give rise to?

cremaster m

what does the genital branch of the genitofemoral n supply?

small area of skin of thigh

what does the femoral branch of the genitofemoral n supply?

obturator n

what n emerges from the medial border of the psoas major m (lumbar plexus)?

cross the pelvic brim in front of the sacroiliac joint, passes behind the iliac vessels and leaves the pelvis through the obturator foramen

describe the course of the obturator n

medial thigh mm

what does the obturator n supply?

ventral rami of lumbar spinal nn L4-L5 and sacral spinal nn S1-S3

what is the sacral plexus formed from?

posterior thigh, foot, most of lower leg and part of pelvis

what does the sacral plexus provide motor and sensory innervation to?

lumbosacral trunk

what is the contribution to the sacral plexus from L4-L5 known as?

piriformis m

what does the sacral plexus lie anterior to?

internal iliac vessels and rectum

what does the sacral plexus lie posterior to?

superior gluteal n (L4, L5, S1), n to piriformis (S1, S2), inferior gluteal n (L5, S1, S2)

what are the branches from the posterior division of the sacral plexus?

posterior femoral cutaneous n (S1, S2, S3)

what are the branches from both the anterior and posterior divisions of the sacral plexus?

seven

how many branches of the sacral plexus leave the pelvis through the greater sciatic foramen?

superior gluteal n

what is the uppermost branch of the sacral plexus?

gluteus medius and minimus mm and tensor fasciae latae mm

what does the superior gluteal n supply?

below superior gluteal n

where does the inferior gluteal n branch off of the sacral plexus?

gluteus maximus m

what does the inferior gluteal n supply?

largest branch of the sacral plexus and largest n in the body

what is the sciatic n?

tibial division, common fibular division

what two parts is the sciatic n comprised of?

through greater sciatic foramen

how does the sciatic n enter the gluteal region?

sciatic n

what n is usually inferior to the piriformis m but may pierce the m?

false

true or false: the sciatic nerve supplies the gluteal region

gluteus maximus m and biceps femoris m

the sciatic n runs deep to what?

mm of posterior thigh

what does the sciatic n supply?

people who frequently perform external rotation of leg i.e. pregnant women and truck drivers

who is more likely to develop sciatica?

common fibular n and tibial n

what does the sciatic n divide into at the popliteal fossa?

tibial

the n to obturator internus branches off of the ___ part of the sciatic n

above the quadratus femoris

where does the n to obturator internus branches off of the tibial part of the sciatic n

obturator internus m and superior gemellus m

what mm does the n to obturator internus supply?

tibial (qf)

the n to quadratus femoris branches off the ___ part of the sciatic n

quadratus femoris m and inferior gemellus m

what mm does the n to quadratus femoris supply?

skin of buttock and back of the thigh

what does the posterior cutaneous n of the thigh supply?

exits the pelvic cavity via the greater sciatic foramen and reenters via the lesser sciatic foramen

how does the pudendal n course?

superior lateral quadrant of gluteal region

what is the safe zone for dorsogluteal intermuscular injections?

sciatic n (inf)

injections in the inferior quadrants of the gluteal region can damage what?

superior gluteal vessels and n

injections in the superior medial quadrants of the gluteal region can damage what?

tibial n (l)

what is the larger of the two branches of the sciatic n?

all the mm of the posterior compartment of the leg

what does the tibial n supply?

soleus m

the tibial n courses through the leg deep to the...

passes posterior to medial malleolus and deep to flexor retinaculum

describe the course of the tibial n into the foot

medial and lateral plantar nerves

what two terminal does the tibial n divide into under the flexor retinaculum?

anteriorly with lateral plantar a

how does the lateral plantar n run?

anteriorly with medial plantar a

how does the medial plantar n run?

common fibular n

what is the lateral and smaller of the two terminal branches of the sciatic n?

just below the neck of the fibula within the head of the fibularis longus m

where does the common fibular n end?

deep fibular n, superficial fibular n

what are the two terminal branches of the common fibular n?

anterior to the interosseous membrane along with the anterior tibial a

how does the deep fibular n descend the leg?

deep

the deep fibular n passes through the foot ___ to the extensor retinaculum

superficial

the superficial fibular n passes through the foot ___ to the extensor retinaculum

mm of the anterior compartment of the leg

what does the deep fibular n supply?

anterolateral to the fibula and becomes superficial in the distal third of the leg

how does the superficial fibular n descend the leg?

mm of the lateral compartment of the leg

what does the superficial fibular n supply?

saphenous n

what is the cutaneous branch of the femoral n?

adductor canal

where is the saphenous n found in the thigh?

great saphenous v

what does the saphenous n descend the leg with?

anterior to medial malleolus

how does the saphenous n pass onto the foot?

cutaneous n

what kind of n is the sural n?

tibial and common fibular nn

the sural n is formed by branches of what nn?

small saphenous v

what does the sural n run with?

lateral malleolus

what does the sural n descend behind?

superior gluteal n, inferior gluteal n, sciatic n, n to obturator internus, n to quadratus femoris, posterior cutaneous n of thigh, pudendal n

list branches of sacral plexus