Lumbosacral Plexus

Question 1

How is the lumbar plexus formed ?

Answer 1

• Within the psoas major muscle
• Formed by the ventral rami of L1-3 & the sup part of L4 spinal nerves
• %50 of cases show a contribution from T12 (subcostal nerve)

Question 2

What are the major branches of the lumbar plexus ?

Answer 2

• Iliohypogastric nervous .
• Ilioinguinal nervous .
• Genitofemoral nervous.
• Lateral cutaneous nerve of the thigh
• Femoral nerve .
• Obturator nerve .

Question 3

What is the largest branch of the lumbar plexus ?

Answer 3

(L2-4):
- obturator nerve
- femoral nerve

Question 4

Where dose the obturator nerve (L2,L3,L4) pass from ?

Answer 4

• descends through the psoas major muscle
• pierces the psoas fascia
• crosses the sacroiliac joint
• emerges from the obturator canal
• takes cutaneous innervation of medial part of thigh
• motor innervation to the adductor muscles of thig

Question 5

Where dose the femoral nerve (L2,L3,L4) ?

Answer 5

• emerges between the psoas major and iliacus m
• thickest branch Cutaneous branches:
• Medial cutaneous n of thigh
• Intermediate cutaneous n of thigh
• Saphenous n
Motor branches:
• Muscles located at the anterior part of thigh
• Pectineus muscle

Question 6

Where are the Iliohypogastric nerve & Ilioinguinal nerve derived from ?

Answer 6

areboth derived from T12-L1-often by a common stem

Question 7

What is the function of the Iliohypogastric nerve (T12, L1) ?

Answer 7

• it sends a “lateral branch” to supply the skin of the gluteal region

• acts as the “ant. branch” to the skin of the hypogastric region

Question 8

Where is the gentifemoral nerve (L1,L2) ?

Answer 8

-runs along the anterior surface of the psoas major muscle
-Feeding into the femoral branch, genital branch

Question 9

Where dose the femoral cutaneous nerve (L2,L3) pass through ?

Answer 9

It passes through the psoas major muscle, iliac crest

Question 10

What is the function of the lateral femoral cutaneous nerve ?

Answer 10

It supplies skin over the anterior and lateral thigh

Question 11

What is the lumbosacral plexus formed from ?

Answer 11

• nerve plexus in the lumbar and sacral region. - the ventral rami L1-L3 nerves and the superior branch of L4 form the LUMBAR PLEXUS
• inferior branch of L4 and all L5 form the LUMBOSACRAL TRUNK and it descends to the SACRAL PLEXUS

Question 12

Where is the sacral plexus located ?

Answer 12

It is located in the lesser pelvis ( true pelvis )

Question 13

What is the sacral plexus related to ?

Answer 13

It is closely related to the piriformis muscle

Question 14

What is the sacral plexus formed by ?

Answer 14

It is formed by :
- lumbosacral trunk
– ventral rami of the S1-3
– part of S4

Question 15

How do the branches of the sacral plexus leave the pelvis ?

Answer 15

Through the greater sciatic foramen- except for the nerve of the piriformis muscle

Question 16

What is the sciatic nerve ( L4,L5,S1,S2,S3) ?

Answer 16

It is the main branch of the sacral plexus, it is the largest nerve and it converts on the interior surface of the pirifomis muscle

Question 17

What is the projection of the sciatic nerve ?

Answer 17

It enters the glory region and passes through the greater sciatic foremen

Question 18

What does the sciatic nerve supply?

Answer 18

It usually supplies no structures in the gluteal region

Question 19

What are the two terminal branches of the sciatic nerve?

Answer 19

-Tibial
- Common fibular (peroneal):
• Superficial peroneal
• Deep peroneal

Question 20

How are the tibial nerve and the common fibular nerve (sciatic nerves) bound?

Answer 20

They are bound together in the same epineurium they usually separate from each other halfway of the thigh.

Question 21

Where is there pudendal nerve located at?

Answer 21

It is most immediately located at the inferior edge of the piriformus muscle . As it intervenes the structures in the perineum.

Question 22

What is the function of the posterior femoral cutaneous nerve (S2,S3)?

Answer 22

It’s supplies, the cutaneous intervention of the inferior part of the glutes region and the posterior side of the thigh and proximal part of the leg

Question 23

Where does the posterior femoral cutaneous nerve pass-through?

Answer 23

The infrapiriform foramen.

Question 24

Where does the superior gluten nerve (L4, L5, S1) pass through?

Answer 24

It versus through the greater sciatic foremen ( suprapiriform foramen ) along the superior gluteal vessels ?

Question 25

What does the superior gluten nerve intervate ?

Answer 25

It intervenes the gluteus medias, minimus and tenor facia lateral muscle.

Question 26

How dose the inferior gluteal nerve ( L5, S1, S2 ) leave the pelvis ?

Answer 26

It Leaves the pelvis at the inferior part of the greater sciatic foramen (infrapiriform foramen) alongside the inferior gluteal vessels.

Question 27

What dose the inferior gluteal nerve innervate ?

Answer 27

innervates the gluteus maximus muscle

Question 28

Where dose the nerve to quadratus femoris muscle (L4, L5, S1) innervate ?

Answer 28

Innervation of the quadrates femoris muscle .

Question 29

What dose the nerve to obtuctor internus muscle ( L5, S1, S2 ) innervate ?

Answer 29

innervation ofobturator internus muscle

Question 30

What is the Coccygeal plexus made from ?

Answer 30

Ventral rami of the :

• S4,S5, and coccygeal spinal nerves
• cutaneous innervation of coccygeal region