Lower Limb 2.1 Flashcards
What is a nerve plexus?
formed when peripheral spinal nerve roots merge and split to produce a network of nerves from which new multi-segmental peripheral nerves emerge
Which plexus supplies the lower limb?
Lumbosacral plexus
What are the three main nerves emerging in the lumbar plexus?
- Lateral cutaneous nerve of the thigh
- Femoral nerve
- Obturator nerve
What do fibres from L4 and L5 form?
lumboscacral trunk which contributes fibres to a number of nerves formed in the sacral plexus
What are the main nerves of the sacral plexus?
- Superior gluteal nerve
- Inferior gluteal nerve
- Sciatic nerve
- Posterior cutaneous nerve of the thigh
What is the sciatic nerve made out of?
- common perineal part
2. tibial part
Where does the femoral nerve arise and course?
- courses infralaterally from the lumbar region through the pelvis
- Giving branches to illiacus muscle
- Exits the pelvis under the inguinal ligament
- To enter the anterior thigh where it supplies the anterior compartment
Where does the obturator nerve arise and innervate?
- arises in the lumbar region 2. passes inferiorly peircing the obturator membrane
- To pass through the obturator foramen and into the medial thigh
- There it innervates the adductor compartment muscles
What is the largest nerve in the body?
Sciatic nerve
What is the sciatic nerve formed from?
L4, L5, S1, S2, S3
What is the course of the sciatic nerve?
- passes from the interior of the pelvis
- Through the greater sciatic foramen into the gluteal region
- Usually inferiorly to one of the small muscles, piriformis 4. Then courses deep the gluteus maximus and into the posterior thigh
What courses close to the sciatic nerve?
posterior cutaneous nerve of thigh
What is the femoral nerve made from?
L2, L3, L4
What does the femoral nerve supply?
Anterior compartment of thigh
What is the obturator nerve made from?
L2, L3, L4
What does the obturator nerve supply?
medial (adductor) compartment of thigh
What does the sciatic nerve / terminal branches) supply?
remaining compartments (posterior thigh, anterior and posterior leg and foot)
What is the terminal branch of the femoral nerve?
saphenous nerve
What does the saphenous nerve supply?
cutaneous nerve supplying anterior medial leg and medial foot
Does the femoral and obturator nerve have cutaneous branches?
Yes to their respective regions
What is the piriformis muscle?
One of the lateral rotator group of gluteal muscles
Why is the piriformis muscle important?
Important anatomicla landmark in relation to nerve and vessels of gluteal region
How do nerves and vessels pass between the buttock and inferior pelvis?
superiorly and inferiorly to the piriformis
What does the superior gluteal nerve innnervate and course?
enters the buttock above piriformis to innervate gluteus medius and minimus and tensor facia lata
What does the inferior gluteal nerve innnervate and course?
inferior the piriformis and supplies gluteus Maximus only
How does the sciatic and posterior cutaneous nerve of the thigh enter the buttock?
inferiorly to piriformis
What does the sciatic nerve supply?
hamstring muscles
What is the course of the sciatic nerve?
deep to gluteus Maximus and enters the posterior thigh deep to the hamstring muscles
Where does the sciatic nerve divide?
- distal part of the thigh
- these nerves pass through the space behind the knee (popliteal fossa) before continuing into the leg
What is the course of the common peroneal nerve?
- courses laterally to wind around the neck of the fibula just inferior to its head
- Here it is relatively superficial and can be palpated
- also means it is susceptible to injury at this point
What happens to the common peroneal nerve as it winds around the fibula neck?
- gives off a lateral cutaneous branch to the leg then bifurcates to form its terminal branches:
1. the superficial
2. deep peroneal nerves
What does the superficial peroneal nerve supply?
- lateral compartment (peroneus longus and brevis)
2. cutaneous innervation to the distal anterior leg and the dorsum of the foot
What does the deep peroneal nerve supply?
- courses inferiorly to supply the anterior compartment muscles and the muscles of the dorsum of the foot
- Gives cutaneous innervation to the cleft between the first and second toes
What is the course of the tibial nerve?
exits the popliteal fossa inferiorly to pass distally between the superficial and deep posterior muscle layers
What does the tibial nerve supply?
superficial and deep muscle compartments posterior leg
What is the course of the tibial nerve at the ankle?
passes posteriorly to medial malleolus to enter foot
What does the tibial nerve do as it enters the foot?
bifurcates to form medial and lateral plantar nerves
What do the plantar nerves do?
supply the intrinsic foot muscles and most of the skin of the sole of the foot
Why are the dermatome filed of anterior lower limb oblique?
due to the permentant pronation
How do you remember L3 and L4 dermatome?
L3 to the knee and L4 to the foor
What are autonomous sensory zones?
Regions of non-overlapping sensory supply from an individual root
Do all nerve roots have an autonomous zone?
no
Why are autonomous zones clinically important?
clinically these zones are where pain and abnormal sensations can be attributes to a single spinal root
Do the peripheral and dermatome nerve fields match?
No
Why do the fields not match?
-peripheral nerves being formed in a plexus
-fibres from spinal roots are intermingled in a plexus and most of the peripheral nerves contain fibres form more than one spinal nerve
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