innervation of lower limbs

Question 1

The lumbar plexus is composed of…

Answer 1

The ventral rami of L1-L4

Question 2

The subcostal nerve arises from…

Answer 2

T12

Question 3

The “superior” divisions of L1 give rise to…

Answer 3

The iliohypogastric + ilioinguinal nerves

Question 4

The genitofemoral nerve is formed by…

Answer 4

The “inferior” division of L1 and the “superior” division of L2

Question 5

The obturator nerve arises from…

Answer 5

The anterior divisions of L2, L3 and L4

Question 6

The femoral nerve arises from …

Answer 6

The posterior divisions of L2, L3 and L4

Question 7

The “posterior” posterior divisions of L2 and L3 give rise to a nerve. Name it

Answer 7

Lateral femoral cutaneous nerve

Question 8

The obturator nerve runs … to the psoas major

Answer 8

First posterior and then medial

Question 9

As the obturator nerve descends, it enters into…

Answer 9

The lesser pelvis

Question 10

Once it’s in the lesser pelvis, the obturator nerve branches into…

Answer 10

Anterior + posterior branches

Question 11

The anterior branch of the obturator nerve innervates…

Answer 11

The adductor longus + brevis, gracilis

Question 12

Which muscles “cover” the anterior branch of the obturator nerve?

Answer 12

Adductor longus + pectineus (anteriorly)

Obturator externus + adductor brevis (posteriorly)

Question 13

The posterior branch of the obturator nerve innervates 2 adductors. Name them

Answer 13

Obturator externus + adductor magnus

Question 14

Name the muscle that is pierced by the posterior branch of the obturator nerve as it descends towards the medial portion of the thigh

Answer 14

Obturator externus

Question 15

Describe the position of the femoral nerve with regards to the psoas major as it descends

Answer 15

It originates posterior to it, more laterally than the obturator nerve + then descends in the groove between the psoas and iliacus to the femoral triangle

Question 16

Describe the alignment of the vessels and nerves in the femoral triangle

Answer 16

VAN from medial to lateral
BUT: then the femoral artery + saphenous nerve cross medially
in the end, the vein + artery are on top of each other & the saphenous nerve is medial

Question 17

Name the muscles that are innervated by the motor branches of the femoral nerve

Answer 17

Sartorius, pectineus + quadriceps

Question 18

The saphenous nerve arises from…

Answer 18

The most medial fibres of the femoral nerve

Question 19

Explain the trajectory of the saphenous nerve from thigh to knee

Answer 19

It runs obliquely and crosses over the femoral artery towards the adductor hiatus. Once it reaches the vastoadductor septum, it lays completely anterior + medial to both vessels. Also anterior to the adductor magnus.
It then becomes more superficial (already at the level of the leg) and runs between the sartorius and gracilis.
It branches into the infrapatellar branch (goes anterior)

Question 20

Describe the trajectory of the saphenous nerve from knee to foot

Answer 20

It descends medially, pretty straight, alongside the greater saphenous vein. At the level of the ankle, it passes anterior to the medial malleolus + the dorsum of the foot

Question 21

The lumbosacral plexus is formed by the rami of…

Answer 21

L4, L5, S1-S5

Question 22

What is the name of the “structure” formed by L4 and L5?

Answer 22

Lumbosacral trunk

Question 23

The common fibular nerve arises from…

Answer 23

The dorsal division of the lumbosacral

plexus

Question 24

The tibial nerve arises from…

Answer 24

The ventral division of the lumbosacral plexus

Question 25

Name the nerve that innervates the gemellus superior + obturator internus

Answer 25

Nerve to obturator internus

Question 26

Name the nerve that innervates the gemellus inferior + quadratus femoris

Answer 26

Nerve to quadratus femoris