Nerves of lower limb

Question 1

Which spinal segments contribute to the lumbar plexus?

Answer 1

Ventral rami L1-4

Question 2

Where is the lumbar plexus situated?

Answer 2

Within psoas major

Question 3

Describe the position of the terminal branches of the lumbar plexus as they emerge from psoas?

Answer 3

From lateral border: iliohypogastric and ilioinguinal, lateral cutaneous nerve of thigh, femoral nerve

Onto anterior surface: genitofemoral nerve

Medial border: obturator nerve

Question 4

Describe the pathway of the iliohypogastric and ilioinguinal nerves?

Answer 4

From lateral border of psoas > emerge onto QL > slip into neurovascular plane where QL meets fascia

Question 5

What do the iliohypogastric and ilioinguinal nerves innervate?

Answer 5

Cuatneous supply: inguinal region and front of scrotum

Motor supply: lowermost fibres of IO and TA

Question 6

Describe the outcome of injury to iliohypogastric and ilioinguinal nerve?

Answer 6

Indirect inguinal hernia

Question 7

Describe the spinal segments that contribute to each of the terminal branches of the lumbar plexus?

Answer 7

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

Question 8

Describe the pathway of the lateral cutaneous nerve of thigh?

Answer 8

Emerges from lateral border of psoas > onto iliacus > swings wide and tucks into ASIS beneath inguinal ligament

Question 9

Describe the consequences of the pathway of the lateral cutaneous nerve of thigh?

Answer 9

In pregnant women and morbidly obese people, can become compressed against inguinal ligament > pins and needles in thigh

Question 10

Describe the pathway of the femoral nerve?

Answer 10

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

Question 11

Describe the breakdown of the genitofemoral nerve?

Answer 11

Two nerves in one sheath

Genital branch: L2

Femoral branch: L1

Question 12

Describe what each branch of the genitofemoral nerve supplies?

Answer 12

Genital branch: spermatic cord

Femoral branch: skin immediately beneath inguinal ligament (over femoral triangle)

Question 13

Which spinal segments contribute to the sacral plexus?

Answer 13

S1-4

Question 14

Which spinal segments contribute to the lumbosacral trunk?

Answer 14

L4,5 and S1-4

Question 15

Which muscular sturcture does the scaral plexis lie on?

Answer 15

Piriformis

Question 16

Where does the lumbosacral trunk join S1-4?

Answer 16

Piriformis

Question 17

What does the femoral nerve supply?

Answer 17

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

Question 18

How does the femoral nerve relate to other structures in the femoral triangle?

Answer 18

Lateral to vascular structures

Outside femoral sheath (sheath contains vein, artery and canal)

Question 19

Describe the sensory innervation of the femoral nerve?

Answer 19

Anterior cutaneous branches of femoral nerve > intermediate and medial cutaneous nerve of thigh

Saphenous nerve > infrapatellar branch and medial crural cutaneous branches

Question 20

Describe the pathway of the obturator nerve?

Answer 20

Emerges from medial border of psoas > lateral wall of pelvis > obturator canal > medial compartment of thigh

Question 21

What does the obturator nerve innervate?

Answer 21

MOTOR: adductor muscles (+ pectineus, - hamstring part of adductor magnus)

SENSORY: inferomedial thigh, pelvic peritoneum

Question 22

Describe the divisions of the obturator nerve?

Answer 22

After it exits obturator canal divides into:

Anterior division: between adductor longus and adductor brevis

Posterior division: between adductor brevis and adductor magnus

Question 23

Which spinal segments contribute to the sciatic nerve?

Answer 23

L4,5, S1,2,3

Anterior and posterior divisions

Question 24

Describe the pathway of the sciatic nerve?

Answer 24

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

Question 25

What does the sciatic nerve supply?

Answer 25

MOTOR: hamstrings (all tibial excpet SHOB) SENSORY: via terminal branches only

Question 26

Describe where the sciatic nerve lies as it passes posterior to the hip joint? What is the consequence of this?

Answer 26

Halfway between medial tuberosity medially and greater trochanter laterally Directly over back of hip joint So, damaged in posterior hip dislocation

Question 27

Describe the components of the sciaitc nerve?

Answer 27

Tibial nerve Common fibular nerve

Question 28

Describe the superior and inferior gluteal nerves, including their pathways and structures that they supply?

Answer 28

SUPERIOR GLUTEAL NERVE: emerges above piriformis, supplies gluteus medius and minimus INFERIOR GLUTEAL NERVE: emerges below piriformis, supplies gluteus maximus

Question 29

Describe the pathway of the posterior cutaneous nerve of thigh? Which structures does it supply?

Answer 29

Emerges beneath sciatic nerve (often unseen) Supplies skin down back of thigh

Question 30

Where does the sciatic nerve divide into its terminal branches?

Answer 30

Varies Commonly at apex of politeal fossa Sometimes divides while it is still in pelvis (common fibular arises above pirifiromis)

Question 31

Describe why intramuscular injections are given in the lateral thigh, and not in the buttocks?

Answer 31

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

Question 32

Describe the innervation of the hamstrings?

Answer 32

Tibial component of sciatic nerve supplies all excpet SHOB SHOB supplied by common fibular component

Question 33

Which spinal segments contribute to the tibial nerve?

Answer 33

L4,5, S1,2,3 Anterior divisions

Question 34

Describe the pathway of the tibial nerve?

Answer 34

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

Question 35

What does the tibial nerve supply?

Answer 35

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)

Question 36

Which spinal segments contribute to the common fibular nerve?

Answer 36

L4,5, S1,2 Posterior divisions

Question 37

Describe the pathway of the common fibular nerve?

Answer 37

Medial to biceps \> superficial to lateral head of gastrocnemius \> winds around neck of fibula \> sinks into substance of fibularis longus \> terminal branches

Question 38

What are the terminal branches of the common fibular nerve?

Answer 38

Deep fibular nerve Superficial fibular nerve

Question 39

What does the common fibular nerve supply?

Answer 39

SENSORY: upper lateral leg via lateral sural cutaneous nerve

Question 40

What does the deep fibular nerve supply?

Answer 40

MOTOR: anterior compartment of leg and EDB SENSORY: 1st toe cleft

Question 41

What does the superificial fibular nerve supply?

Answer 41

MOTOR: lateral compartment of leg SENSORY: lower lateral leg and dorsum of foot

Question 42

Describe the pathway of the deep fibular nerve?

Answer 42

Begins in fibularis longus \> descends deep to EDL, anterior to interosseus membrane \> beneath extensor retinaculum \> dorsum of foot

Question 43

Describe the pathway of the superificial fibular nerve?

Answer 43

Descends in lateral compartment of leg \> supplies fibulairs longus \> becomes superificial to supply skin over lower lateral leg and dorsum of foot

Question 44

Describe the innervation of the large muscles in the gluteal region?

Answer 44

Gluteus medius and minimus: supeficial gluteal nerve Gluteus maximus: inferior gluteal nerve

Question 45

Describe the innervation of the muscles of the anterior compartment of the thigh?

Answer 45

Femoral nerve

Question 46

Describe the innervation of the muscles of the medial compartment of the thigh?

Answer 46

Obturator nerve

Question 47

Describe the innervation of the muscles of the posterior compartment of the thigh?

Answer 47

Tibial part of sciatic nerve (except SHOB)

Question 48

Describe the innervation of the muscles of the posterior compartment of the leg?

Answer 48

Tibial part of sciatic nerve

Question 49

Describe the innervation of the muscles of the sole of the foot?

Answer 49

Tibial part of the sciatic nerve

Question 50

Describe the innervation of the muscles of the anterior compartment of the leg?

Answer 50

Common fibular part of sciatic nerve

Question 51

Describe the innervation of the muscles of the lateral compartment of the leg?

Answer 51

Common fibular part of sciatic nerve

Question 52

Describe the innervation of the muscles in the dorsum of the foot?

Answer 52

Common fibular part of the sciatic nerve

Question 53

Describe the sensory innervation to the lower limb?

Answer 53

Question 54

Describe the dermatomes of the lower limb?

Answer 54

Question 55

Describe the myotomes of the lower limb?

Answer 55