Lecture 11: Lumbosacral Plexus Flashcards
What are enlargements of spinal cord
Cervical and lumbar
Correspond with plexus involved in providing innervation to limbs
Enlargements reflect increased numbers of neurons (motor and sensory) coming from/going to limbs
Describe cervical enlargemnt
Brachial plexus
C5-t1
Describe lumbar enlargemnt
Lumbosacral plexus = l1-s4
Swelling higher than nerve levels here, bc have to travel far
Describe what lumbar plexus means
After emerging from spinal cord =nerves cross over, join, plait/braid and travel together for a time and may divide again further in the limb
Usually nerves = combos of diff spinal levels
What is lumbosacral plexus composed of
Anterior rami of spinal nerves l1-s4 - divided into 2 parts = lumbar plexus and sacral plexus
name spinal levels of lumbar plexus
L1-l4
And t12 contributes a bit
Describe cutaneous innervation = lumbar plexus
Innervates anterior, medial and lateral thigh, anterior knee and medial leg and foot (ankle)
Describe motor innervation = lumbar plexus
Innervation to anterior and medial compartments of thigh
Nothing below knee tho
Name levels of sacral plexus
L4-s4
What is special about l4
Split between 2 divisions
Some to lumbar anf some to sacral plexus
Describe cutaneous innervation = sacral plexus
Innervation to lower buttocks, posterior thigh (post cutaneous) and leg, lateral leg and majority of the foot - except small part of ankle
Describe motor innervation = sacral plexus
To gluteal region, posterior thigh compartments of leg and the foot
Everything below knee
Describe iliohypogastric nerve of lumbar plexus = spinal levels
T12-l1
Describe ilioinguinal nerve of lumbar plexus = spinal levels
L1
What is special about iliohypogastric and ilioinguinal nerves of lumbar plexus
Pierce abdominal walll = no passage through pelvis, stay near iliac crest
Describe genitofemoral nerve of lumbar plexus = spinal levels
L1-l2
Describe obturator nerve of lumbar plexus = spinal levels
L2-l4
Exits pelvis via obturator foramen
Describe lateral femoral cutaneous nerve of lumbar plexus = spinal levels
L2-3
Under inguinal ligament to thigh
In iliac fossa
Describe femoral nerve of lumbar plexus = spinal levels
L2-l4
Anterior thigh
Where AND WHICH NERVES = how do lumbar plexus nerves exit generally
Genitofemoral
Lateral femoral cutaneous
Femoral
= all exit pelvis anteriorly through spaces in inguinal region
Where do sacral plexus nerves exit/enter pelvis
Collectively = exit/enter pelvis posteriorly via greater sciatic foramen
Describe superior and inferior gluteal nerves of sacral plexus = spinal levels
Superior = l4-s1
Inferior gluteal = l5-s2
Describe pudendal nerve of sacral plexus = spinal levels
S2-4
Somatic nerve
Describe posterior femoral cutaneous nerve of sacral plexus = spinal levels
S1-3
Describe sciatic nerve of sacral plexus = spinal levels
L4-s3
Largest nerve in body
Describe inguinal Canal generally
Fascial canal acting as conduit between internal pelvis and external genitalia and surrounding skin
Asis —> pubic tubercle = inguinal lig (made by external oblique/abd muscles aponeurosis )
Describe spaces of inguinal region
On anterior side
Neurovasculature and hip muscles exit/enter pelvis via 3 spaces to get to/from lower limb and groin
Name the 3 spaces of inguinal region
Muscular compartment = most lateral
Vascular compartment
Inguinal canal - superior to inguinal ligament
What goes through muscular compartment
Iliopsoas
Lateral femoral cutaneous nerve
Femoral nerve
What goes through vascular component
Femoral a and v
Genitofemoral nerve (femoral branch of this nerve)
Lymph nodes
What goes through inguinal canal
Fascial space=tunnel, pelvis to genital region
Spermatic cord - amab, round ligament of uterus - afab
Ilioinguinal nerve
Genitofemoral nerve (genital branch of this nerve)
Name levels of ilio hypogastroc, inguinal and genitofemoral nerves
T12-l2
Describe iliohypogastric nerve
T12-l1
Behind psoas major, in front of quadratus
Pierces lateral abd wall - through all muscles - above iliac crest then splits
= lateral branch towards tensor fascia lata and anterior branch = close to pubic tubercle (comes out between transversus abdominals and internal oblique)
Describe ilioinguinal nerve
L1
Behind psoas, in front of quadratus
Pierces abd wall but stays between transversus abd and internal oblique - goes through inguinal canal
What is function of ilioinguinal and iliohypogastric nerves
Motor to lower internal obliques and transversus abdominus - abd wall
Describe genitofemroal nerve
L1-2
Will divide when pierces psoas major
= femoral branch travels under inguinal ligament into vascular space - to ant thigh, goes over femur
= genital branch = travels in inguinal canal, joints ilioinguinal then both come out
Describe genitofemroal nerve = function
Motor cremaster muscle in spermatic cord - only genital branch
Describe sensory functions of ilio hypogastroc, inguinal and genitofemoral nerves
Skin over upper lateral thigh and inguinal region = iliohypogastric
Anterior and medial thigh = genitofemoral and ilioinguinal
Scrotum/Labia = genitofemoral and ilioinguinal
Describe motor functions of ilio hypogastroc, inguinal and genitofemoral nerves
Abd wall muscles
No innervation to muscles that move lower limb joints tho = no joint movers, stay local
Describe where lateral femoral cutaneous travels
Close to attachment of inguinal ligament = asis
Travels between psoas and iliacus - along rim of false pelvis over iliacus
Pierces ant abd wall muscles to pass under inguinal ligament near lateral edge of muscular compartment into anterolateral thigh
What is function of lateral femoral cutaneous
Cutaneous = not motor
Sensory to skin over anterolateral thigh, down to knee
Describe clinical correlate of lateral femoral cutaneous nerve
Can be entrapped under inguinal ligament - causes numbness, pain and/or tingling in lateral thigh = meralgia paresthetica or skinny pants syndrome
Describe obturator nerve pathway
mixed nerve
Travels between psoas and iliacus (behind all of psoas), over pelvic brim into lateral wall of true pelvis - through obturator foramen (along with vasculature) into medial thigh
Describe obturator nerve sensory function
From skin of medial thigh and hip joint capsule
- also need for joints = position in space
Sensory doesn’t mean just cutaneous
Describe obturator nerve motor functions
To medial compartment of the thigh (adductors and gracilis) and obturator externus
Describe femoral nerve
MIXED NERVE
Emerges between psoas and iliacus - travels with them - as iliopsoas = under inguinal ligament near medial edge of muscular compartment into thigh
Describe femoral nerve sensory functions
From skin of anterior thigh as anterior femoral cutaneous nerve
From skin of medial leg as saphenous nerve, travelling deep to sartorious muscle
Describe saphenous nerve
Runs with great saphenous vein along medial leg - branch of femoral nerve
Describe femoral nerve Motor functions
To anterior compartment fo thigh - rest fo it =
Quadriceps = adductor of hip but still from femoral nerve, sartorius
Pectineus from medial compartment - via ant femoral cutaneous nerve
What does lumbar plexus mainly innervate
Muscles of anterior and medial thigh
= hip flexors, adductors, knee extensors
Does lumbar plexus innervate muscles below knee
NOOOOOOOOOO
Describe first few branches of lumbar plexus
T12-L2 =mostly cutaneous with no motor role moving lower limb joints
Describe cutaneous distribution of lumbar plexus
Lateral, anterior and medial thigh, also medial leg (saphenous nerve)
Wat does inferior gluteal nerves travel with
Next to sciatic and posterior femoral cutaneous
Describe gluteal nerves generally
Mixed nerves = primarily motor, but have Afferent neurons to relay pain, proprioception etc from the glutes and the hip joint (position of joints in space)
Do not provide cutaneous sensation
Describe sciatic nerve functions
Motor to hamstrings - posterior thigh and to all distal muscles below the knee
Sensory to distal limb below knee, except region covered by saphenous nerve
Describe posterior femoral cutaneous functions
S1-3
Sensory only = cutaneous innervation fo posterior thigh, ends in popliteal region
Describe inferior cluneal function
Branch of posterior femoral cutaneous nerve
Sensory only = to inferior buttocks
Where does sciatic nerve branch
In popliteal region = to tibial and fibular nerves
Describe sural nerve
Sensory nerve from distal branches of sciatic nerve
What does sciatic nerve do for thigh
Provides motor innervation to posterior compartment of thigh - hamstrings, biceps femoris, semitendinosus, semimembranosus, hamstring portion of adductor
But no sensory innervation = all from posterior femoral cutaneous or inferior cluneal
Describe whole pathway of sciatic nerve
Exits pelvis via greater sciatic foramen inf to piriformis
Travels on post surface of hip lateral rotators - deep to gluteus Maximus near gemelli
Dives deep to the hamstrings
In thigh = travels deep to hamstrings, especially long head of biceps femoris - runs whole length of this muscle
Near apex of popliteal fosssa = splits into 2 terminal branches
Describe branching of sciatic - details
In popliteal fossa=
Common fibular nerve = l4-s2
Tibial nerve = l5-s3
Is sciatic branching always at popliteal fossa
NOOOOOOOOOOO
MAY BE separate as early as the greater sciatic foramen
What is function of common fibular nerve
Motor and sensory to anterior and lateral leg, dorsum of foot
Ant anf lat muscles innervated
What is function of tibial nerve
Motor to posterior leg and plantar foot= posterior compartment of leg
sensory to plantar foot
What is function of sural nerves
Cutaneous only to posterior and lateral leg/foot
Below knee
Lateral Sural nerve and medial sural nerve combine to form sural nerve
What gives lateral sural nerve
Common fibular nerve
What give medial sural nerve
Tibial nerve
