W29-L1: Nerves of the lower leg

Question 1

Where is the lumbar plexus?

Answer 1

Within psoas major

Question 2

What makes up the lumbar plexus?

Answer 2

Ventral rami of L1-4

Question 3

What nerves arise from the lateral border of psoas major?

Answer 3

-Illioinguinal and iliohypogastric nerves (onto quadratus lumborum)
-lateral cutaneous nerve of thigh
-femoral nerve
(both onto illiacus)

Question 4

What rami give rise to Illioinguinal and iliohypogastric nerves ?

Answer 4

L1

Question 5

What rami give rise to the lateral cutaneous nerve of thigh?

Answer 5

L2,3

Question 6

What rami gives rise to femoral nerve?

Answer 6

L2,3,4

Question 7

What do Illioinguinal and iliohypogastric supply?

Answer 7

cutaneous to inguinal area and motor to arching fibres of internal fibres and transverse oblique

Question 8

What does damage to Illioinguinal and iliohypogastric mean?

Answer 8

they can’t contract and bring the roof of the inguinal canal and prevent hernias

Question 9

What nerve arises onto the anterior surface of psoas major?

Answer 9

Genitofemoral nerve (L1,2)

Question 10

What nerve arises onto the medial surface of psoas major?

Answer 10

Obturator nerve (L2,3,4)

Question 11

Where does lateral cutaneous nerve of thigh run?

Answer 11

runs into anterior compartment of thigh and tucks in next to ASIS beneath inguinal ligament

Question 12

What is the role of the femoral nerve?

Answer 12

motor to anterior compartment of the thigh and sensory to anteromedial thigh and medial side of knee, leg and ankle

Question 13

What are the two branches of the gentiofemoral nerve?

Answer 13

• L1 is femoral branch of supplies area of skin immediately beneath inguinal ligament
• L2 is genital branch, supplies the spermatic cord

Question 14

Where is the sacral plexus formed?

Answer 14

Piriformis from S1-4 and contribution from lumbar, L4 whats left over and doesnt contribute to lumbar plexus and L5

Question 15

How does the femoral nerve supplies each muscle?

Answer 15

breaks into key terminal branches for each muscle it supplies

Question 16

Where is the obturator cutaneous supply?

Answer 16

Medial side just superior to the knee

Question 17

What is the obturator nerve motor supply?

Answer 17

Adductor muscles

Question 18

How does the obturator run in the leg?

Answer 18

splits into anterior and posterior branches, one each side of adductor brevis (in front btwn it and longus and it and magnus), as well as a branch off to gracilis

Question 19

What supplies the pelvis peritoneum and where is pain referred to as a consequence?

Answer 19

Obturator, medial thigh above the knee

Question 20

What makes up the sciatic nerve?

Answer 20

Tibial and common fibular components

Question 21

How does the sciatic nerve run?

Answer 21

exits pelvis via greater sciatic foramen, emerges beneath piriformis posterior to hip joint, descends on the posterior thigh and divides at the apex of popliteal fossa

Question 22

What does the sciatic nerve supply before it divides?

Answer 22

Hamstrings (except for short head of biceps-fibular)

Question 23

How can you damage the sciatic nerve?

Answer 23

Posterior dislocation of the hip

Question 24

What nerve does gluteas medius and maximus?

Answer 24

Superior gluteal

Question 25

What nerve does the gluteus maximus?

Answer 25

Inferior gluteal

Question 26

What is the path of the tibial nerve?

Answer 26

Vertical descent through popliteal fossa
beneath fibrous arch of Soleus, descends on Tibialis Posterior in calf, posterior to medial malleolus, sole of foot then becomes medial and lateral plantar nerves

Question 27

What is motor supply of the tibial nerve?

Answer 27

Posterior leg and sole of foot

Question 28

What is the sensory supply of the tibial nerve?

Answer 28

posterior leg (sural nerve) and sole of foot (medial calcaneal, medial and lateral plantar nerves)

Question 29

What is the course of the common fibular nerve?

Answer 29

medial to biceps then superficial to lateral headof Gastrocnemius, winds round the neck of the fibula then Fibularis Longus, terminal branches

Question 30

What does the common fibular nerve do?

Answer 30

Sensory to upper lateral leg via lateral sural cutaneous nerve, terminal divisions provide motor

Question 31

What does the deep fibular do?

Answer 31

Motor to anterior compartment of leg and EDB and sensory to 1st toe cleft

Question 32

What does the superficial fibular do?

Answer 32

motor to lateral compartment of leg and sensory to lower lateral leg and
dorsum of foot

Question 33

What does a fracture to the neck of the fibular cause?

Answer 33

Damages common fibular nerve and so get a dropped foot (can’t dorsiflex or evert)

Question 34

What do you need to know the dermatomes?

Answer 34

map segmental supply to show damage back at the level of the plexus rather than at peripheral nerve