Nerves of lower limb Flashcards
Which spinal segments contribute to the lumbar plexus?
Ventral rami L1-4
Where is the lumbar plexus situated?
Within psoas major
Describe the position of the terminal branches of the lumbar plexus as they emerge from psoas?
From lateral border: iliohypogastric and ilioinguinal, lateral cutaneous nerve of thigh, femoral nerve
Onto anterior surface: genitofemoral nerve
Medial border: obturator nerve
Describe the pathway of the iliohypogastric and ilioinguinal nerves?
From lateral border of psoas > emerge onto QL > slip into neurovascular plane where QL meets fascia
What do the iliohypogastric and ilioinguinal nerves innervate?
Cuatneous supply: inguinal region and front of scrotum
Motor supply: lowermost fibres of IO and TA
Describe the outcome of injury to iliohypogastric and ilioinguinal nerve?
Indirect inguinal hernia
Describe the spinal segments that contribute to each of the terminal branches of the lumbar plexus?
Iliohypogastric and ilioinguinal nerves: L1
Lateral cutaneous nerve of thigh: L2,3
Femoral nerve: L2,3,4
Genitofemoral nerve: L1,2
Obturator nerve: L2,3,4
Describe the pathway of the lateral cutaneous nerve of thigh?
Emerges from lateral border of psoas > onto iliacus > swings wide and tucks into ASIS beneath inguinal ligament
Describe the consequences of the pathway of the lateral cutaneous nerve of thigh?
In pregnant women and morbidly obese people, can become compressed against inguinal ligament > pins and needles in thigh
Describe the pathway of the femoral nerve?
Emerges from lateral border of psoas > onto iliacus > tucks into gutter of iliopsoas > continues with converging fibres beneath inguinal ligament > divides into terminal branches just distal to ligament
Describe the breakdown of the genitofemoral nerve?
Two nerves in one sheath
Genital branch: L2
Femoral branch: L1
Describe what each branch of the genitofemoral nerve supplies?
Genital branch: spermatic cord
Femoral branch: skin immediately beneath inguinal ligament (over femoral triangle)
Which spinal segments contribute to the sacral plexus?
S1-4
Which spinal segments contribute to the lumbosacral trunk?
L4,5 and S1-4
Which muscular sturcture does the scaral plexis lie on?
Piriformis
Where does the lumbosacral trunk join S1-4?
Piriformis
What does the femoral nerve supply?
MOTOR: quads, sartorius, pectineus
SENSORY: anteromedial thigh and medial side of knee, leg and ankle
- anterior cutaneous branches (medial and intermediate cutaneous nerve of thigh)
- saphenous nerve
How does the femoral nerve relate to other structures in the femoral triangle?
Lateral to vascular structures
Outside femoral sheath (sheath contains vein, artery and canal)
Describe the sensory innervation of the femoral nerve?
Anterior cutaneous branches of femoral nerve > intermediate and medial cutaneous nerve of thigh
Saphenous nerve > infrapatellar branch and medial crural cutaneous branches
Describe the pathway of the obturator nerve?
Emerges from medial border of psoas > lateral wall of pelvis > obturator canal > medial compartment of thigh
What does the obturator nerve innervate?
MOTOR: adductor muscles (+ pectineus, - hamstring part of adductor magnus)
SENSORY: inferomedial thigh, pelvic peritoneum
Describe the divisions of the obturator nerve?
After it exits obturator canal divides into:
Anterior division: between adductor longus and adductor brevis
Posterior division: between adductor brevis and adductor magnus
Which spinal segments contribute to the sciatic nerve?
L4,5, S1,2,3
Anterior and posterior divisions
Describe the pathway of the sciatic nerve?
Exits pelvis via GSF > emerges beneath piriformis in gluteal region > posterior to hip > descends in posterior thigh under biceps > divides at apex of politeal fossa
What does the sciatic nerve supply?
MOTOR: hamstrings (all tibial excpet SHOB)
SENSORY: via terminal branches only
Describe where the sciatic nerve lies as it passes posterior to the hip joint?
What is the consequence of this?
Halfway between medial tuberosity medially and greater trochanter laterally
Directly over back of hip joint
So, damaged in posterior hip dislocation
Describe the components of the sciaitc nerve?
Tibial nerve
Common fibular nerve
Describe the superior and inferior gluteal nerves, including their pathways and structures that they supply?
SUPERIOR GLUTEAL NERVE: emerges above piriformis, supplies gluteus medius and minimus
INFERIOR GLUTEAL NERVE: emerges below piriformis, supplies gluteus maximus
Describe the pathway of the posterior cutaneous nerve of thigh?
Which structures does it supply?
Emerges beneath sciatic nerve (often unseen)
Supplies skin down back of thigh
Where does the sciatic nerve divide into its terminal branches?
Varies
Commonly at apex of politeal fossa
Sometimes divides while it is still in pelvis (common fibular arises above pirifiromis)
Describe why intramuscular injections are given in the lateral thigh, and not in the buttocks?
Trying to avoid sciatic nerve
Lateral thigh: no chance of sciatic nerve being here
Buttocks: if sciatic has divided early, common fibular nerve will arise above piriformis > in upper quadrant of buttocks
Describe the innervation of the hamstrings?
Tibial component of sciatic nerve supplies all excpet SHOB
SHOB supplied by common fibular component
Which spinal segments contribute to the tibial nerve?
L4,5, S1,2,3
Anterior divisions
Describe the pathway of the tibial nerve?
Vertical descent through popliteal fossa > beneath fibrous arch of soleus > descends on tibialis posterior in calf > posterior to medial malleolus > sole of foot > medial and lateral plantar nerves
What does the tibial nerve supply?
MOTOR: muscles of posterior leg and sole of foot
SENSORY: posterior leg (sural nerve) and sole of foot ( medial calcaneal, medial and lateral plantar nerves)
Which spinal segments contribute to the common fibular nerve?
L4,5, S1,2
Posterior divisions
Describe the pathway of the common fibular nerve?
Medial to biceps > superficial to lateral head of gastrocnemius > winds around neck of fibula > sinks into substance of fibularis longus > terminal branches
What are the terminal branches of the common fibular nerve?
Deep fibular nerve
Superficial fibular nerve
What does the common fibular nerve supply?
SENSORY: upper lateral leg via lateral sural cutaneous nerve
What does the deep fibular nerve supply?
MOTOR: anterior compartment of leg and EDB
SENSORY: 1st toe cleft
What does the superificial fibular nerve supply?
MOTOR: lateral compartment of leg
SENSORY: lower lateral leg and dorsum of foot
Describe the pathway of the deep fibular nerve?
Begins in fibularis longus > descends deep to EDL, anterior to interosseus membrane > beneath extensor retinaculum > dorsum of foot
Describe the pathway of the superificial fibular nerve?
Descends in lateral compartment of leg > supplies fibulairs longus > becomes superificial to supply skin over lower lateral leg and dorsum of foot
Describe the innervation of the large muscles in the gluteal region?
Gluteus medius and minimus: supeficial gluteal nerve
Gluteus maximus: inferior gluteal nerve
Describe the innervation of the muscles of the anterior compartment of the thigh?
Femoral nerve
Describe the innervation of the muscles of the medial compartment of the thigh?
Obturator nerve
Describe the innervation of the muscles of the posterior compartment of the thigh?
Tibial part of sciatic nerve (except SHOB)
Describe the innervation of the muscles of the posterior compartment of the leg?
Tibial part of sciatic nerve
Describe the innervation of the muscles of the sole of the foot?
Tibial part of the sciatic nerve
Describe the innervation of the muscles of the anterior compartment of the leg?
Common fibular part of sciatic nerve
Describe the innervation of the muscles of the lateral compartment of the leg?
Common fibular part of sciatic nerve
Describe the innervation of the muscles in the dorsum of the foot?
Common fibular part of the sciatic nerve
Describe the sensory innervation to the lower limb?
Describe the dermatomes of the lower limb?
Describe the myotomes of the lower limb?
