Lower Limb 2.1

Question 1

What is a nerve plexus?

Answer 1

formed when peripheral spinal nerve roots merge and split to produce a network of nerves from which new multi-segmental peripheral nerves emerge

Question 2

Which plexus supplies the lower limb?

Answer 2

Lumbosacral plexus

Question 3

What are the three main nerves emerging in the lumbar plexus?

Answer 3

1. Lateral cutaneous nerve of the thigh
2. Femoral nerve
3. Obturator nerve

Question 4

What do fibres from L4 and L5 form?

Answer 4

lumboscacral trunk which contributes fibres to a number of nerves formed in the sacral plexus

Question 5

What are the main nerves of the sacral plexus?

Answer 5

1. Superior gluteal nerve
2. Inferior gluteal nerve
3. Sciatic nerve
4. Posterior cutaneous nerve of the thigh

Question 6

What is the sciatic nerve made out of?

Answer 6

1. common perineal part

2. tibial part

Question 7

Where does the femoral nerve arise and course?

Answer 7

1. courses infralaterally from the lumbar region through the pelvis
2. Giving branches to illiacus muscle
3. Exits the pelvis under the inguinal ligament
4. To enter the anterior thigh where it supplies the anterior compartment

Question 8

Where does the obturator nerve arise and innervate?

Answer 8

1. arises in the lumbar region 2. passes inferiorly peircing the obturator membrane
2. To pass through the obturator foramen and into the medial thigh
3. There it innervates the adductor compartment muscles

Question 9

What is the largest nerve in the body?

Answer 9

Sciatic nerve

Question 10

What is the sciatic nerve formed from?

Answer 10

L4, L5, S1, S2, S3

Question 11

What is the course of the sciatic nerve?

Answer 11

1. passes from the interior of the pelvis
2. Through the greater sciatic foramen into the gluteal region
3. Usually inferiorly to one of the small muscles, piriformis 4. Then courses deep the gluteus maximus and into the posterior thigh

Question 12

What courses close to the sciatic nerve?

Answer 12

posterior cutaneous nerve of thigh

Question 13

What is the femoral nerve made from?

Answer 13

L2, L3, L4

Question 14

What does the femoral nerve supply?

Answer 14

Anterior compartment of thigh

Question 15

What is the obturator nerve made from?

Answer 15

L2, L3, L4

Question 16

What does the obturator nerve supply?

Answer 16

medial (adductor) compartment of thigh

Question 17

What does the sciatic nerve / terminal branches) supply?

Answer 17

remaining compartments (posterior thigh, anterior and posterior leg and foot)

Question 18

What is the terminal branch of the femoral nerve?

Answer 18

saphenous nerve

Question 19

What does the saphenous nerve supply?

Answer 19

cutaneous nerve supplying anterior medial leg and medial foot

Question 20

Does the femoral and obturator nerve have cutaneous branches?

Answer 20

Yes to their respective regions

Question 21

What is the piriformis muscle?

Answer 21

One of the lateral rotator group of gluteal muscles

Question 22

Why is the piriformis muscle important?

Answer 22

Important anatomicla landmark in relation to nerve and vessels of gluteal region

Question 23

How do nerves and vessels pass between the buttock and inferior pelvis?

Answer 23

superiorly and inferiorly to the piriformis

Question 24

What does the superior gluteal nerve innnervate and course?

Answer 24

enters the buttock above piriformis to innervate gluteus medius and minimus and tensor facia lata

Question 25

What does the inferior gluteal nerve innnervate and course?

Answer 25

inferior the piriformis and supplies gluteus Maximus only

Question 26

How does the sciatic and posterior cutaneous nerve of the thigh enter the buttock?

Answer 26

inferiorly to piriformis

Question 27

What does the sciatic nerve supply?

Answer 27

hamstring muscles

Question 28

What is the course of the sciatic nerve?

Answer 28

deep to gluteus Maximus and enters the posterior thigh deep to the hamstring muscles

Question 29

Where does the sciatic nerve divide?

Answer 29

• distal part of the thigh

- these nerves pass through the space behind the knee (popliteal fossa) before continuing into the leg

Question 30

What is the course of the common peroneal nerve?

Answer 30

• 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

Question 31

What happens to the common peroneal nerve as it winds around the fibula neck?

Answer 31

• gives off a lateral cutaneous branch to the leg then bifurcates to form its terminal branches:
  1. the superficial
  2. deep peroneal nerves

Question 32

What does the superficial peroneal nerve supply?

Answer 32

1. lateral compartment (peroneus longus and brevis)

2. cutaneous innervation to the distal anterior leg and the dorsum of the foot

Question 33

What does the deep peroneal nerve supply?

Answer 33

1. courses inferiorly to supply the anterior compartment muscles and the muscles of the dorsum of the foot
2. Gives cutaneous innervation to the cleft between the first and second toes

Question 34

What is the course of the tibial nerve?

Answer 34

exits the popliteal fossa inferiorly to pass distally between the superficial and deep posterior muscle layers

Question 35

What does the tibial nerve supply?

Answer 35

superficial and deep muscle compartments posterior leg

Question 36

What is the course of the tibial nerve at the ankle?

Answer 36

passes posteriorly to medial malleolus to enter foot

Question 37

What does the tibial nerve do as it enters the foot?

Answer 37

bifurcates to form medial and lateral plantar nerves

Question 38

What do the plantar nerves do?

Answer 38

supply the intrinsic foot muscles and most of the skin of the sole of the foot

Question 39

Why are the dermatome filed of anterior lower limb oblique?

Answer 39

due to the permentant pronation

Question 40

How do you remember L3 and L4 dermatome?

Answer 40

L3 to the knee and L4 to the foor

Question 41

What are autonomous sensory zones?

Answer 41

Regions of non-overlapping sensory supply from an individual root

Question 42

Do all nerve roots have an autonomous zone?

Answer 42

no

Question 43

Why are autonomous zones clinically important?

Answer 43

clinically these zones are where pain and abnormal sensations can be attributes to a single spinal root

Question 44

Do the peripheral and dermatome nerve fields match?

Answer 44

No

Question 45

Why do the fields not match?

Answer 45

-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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