1.3.1. The Lumbar Plexus

Question 1

What is the Lumbar Plexus?

Answer 1

A network of Nerve Fibers, which supplies the Skin and Musculature of the Lower Limb

Question 2

Which muscle is the Lumbar Plexus related to?

Answer 2

It is located within the Substance of the Psoas Major

Question 3

Where is the Lumbar Plexus located, in relation to the Lumbar Vertebrae?

Answer 3

Anterior to the Transverse Process of the Lumbar Vertebrae

Question 4

What forms the Lumbar Plexus?

Answer 4

1. The Anterior Rami of the of Spinal Nerve L1
2. The Anterior Rami of the of Spinal Nerve L2
3. The Anterior Rami of the of Spinal Nerve L3
4. The Anterior Rami of the of Spinal Nerve L4
   (5. The Anterior Rami of the of Spinal Nerve T12 also contributes)

Question 5

How do the Spinal Nerves leave the Spinal Cord?

Answer 5

Via the Intervertebral Foramina of the Vertebral Column

Question 6

What happens to the Nerves, after they leave the Spinal Cord?

Answer 6

They divide into Anterior and Posterior Fibers (or Rami)

Question 7

What happens to the Anterior Rami of L1-L4?

Answer 7

They intertwine (The Lumbar Plexus) and divide into several cords, which then go on to form the Major Peripheral Nerves of the Lumbar Plexus

Question 8

How many Major Peripheral Nerves of the Lumbar Plexus are there?

Answer 8

6

Question 9

Where do the 6 Peripheral Nerves of the Lower Limb travel?

Answer 9

These descend down the Posterior Abdominal Wall

Question 10

What are the 6 Major Peripheral Nerves of the Lower Limb?

Answer 10

1. Iliohypogastric Nerve
2. Ilioinguinal Nerve
3. Genitofemoral Nerve
4. Lateral Cutaneous Nerve of the Thigh
5. Obturator Nerve
6. Femoral Nerve

Question 11

Where does the Iliohypogastric Nerve travel?

Answer 11

1. It runs across the Quadratus Lumborum Muscle of the Posterior Abdominal Wall, to the Iliac Crest
2. It then perforates the Transverse Abdominis

Question 12

What happens to the Iliohypogastric Nerve after it perforates the Transverse Abdominis?

Answer 12

It divides into its Terminal Branches

Question 13

What is the Segmental (or Root) Value of the Iliohypogastric Nerve?

Answer 13

1. L1

2. (Contributions from) T12

Question 14

What is the motor function of the Iliohypogastric Nerve?

Answer 14

1. Innervation of the Transverse Abdominis

2. Innervation of the Internal Oblique

Question 15

What is the sensory function of the Iliohypogastric Nerve?

Answer 15

Innervation of the Posterolateral Gluteal Skin

Question 16

Is the Ilioinguinal Nerve larger than the Iliohypogastric Nerve?

Answer 16

No

Question 17

Where does the Ilioinguinal Nerve travel?

Answer 17

1. It runs across the Quadratus Lumborum Muscle of the Posterior Abdominal Wall, to the Iliac Crest
2. It then perforates the Transverse Abdominis
3. It then passes through the Superficial Inguinal Ring

Question 18

What is the Segmental (or Nerve Root) Value of the Ilioinguinal Nerve?

Answer 18

L1

Question 19

What is the motor functions of the Ilioinguinal Nerve?

Answer 19

1. Innervation of the Transverse Abdominis

2. Innervation of the Internal Oblique

Question 20

What is the sensory function of the Ilioinguinal Nerve?

Answer 20

1. Innervation of the Skin on the Upper Medial Thigh
2. a) Innervation of the Skin over the Root of the Penis and Anterior Scrotum
3. b) Innervation of the Skin over the Mons Pubis and Labia Majora

Question 21

What happens to the Genitofemoral Nerve, after it leaves the Psoas Major?

Answer 21

It divides into 2 Branches

Question 22

What are the 2 Branches the Genitofemoral Nerve?

Answer 22

1. Genital Branch of the Genitofemoral Nerve

2. Femoral Branch of the Genitofemoral Nerve

Question 23

What is the Segmental (or Nerve Root) Value of the Genitofemoral Nerve?

Answer 23

1. L1

2. L2

Question 24

What is the motor function of the Genital Branch of the Genitofemoral Nerve?

Answer 24

Innervation of the Cremasteric Muscle

Question 25

What is the motor function of the Femoral Branch of the Genitofemoral Nerve?

Answer 25

There is none

Question 26

What is the sensory function of the Genital Branch of the Genitofemoral Nerve?

Answer 26

1. a) Innervation of the Skin over the Anterior Scrotum | 1. b) Innervation of the Skin over the Mons Pubis and Labia Majora

Question 27

What is the sensory function of the Femoral Branch of the Genitofemoral Nerve?

Answer 27

The Skin on the Upper Anterior Thigh

Question 28

Where does the Lateral Cutaneous Nerve of the Thigh, enter the Thigh?

Answer 28

At the Lateral Aspect of the Ilioinguinal Ligament

Question 29

What is the Segmental (or Nerve Root) Value of the Lateral Cutaneous Nerve of the Thigh?

Answer 29

1. L2 | 2. L3

Question 30

What is the motor function of the Lateral Cutaneous Nerve of the Thigh?

Answer 30

There is none

Question 31

What is the sensory function of the Lateral Cutaneous Nerve of the Thigh?

Answer 31

1. Innervation of Anterior Thigh, down to the level of the Knee 2. Innervation of Lateral Thigh, down to the level of the Knee

Question 32

What is the Segmental (or Nerve Root) Value of the Obturator Nerve?

Answer 32

1. L2 2. L3 3. L4

Question 33

Where does the Obturator Nerve travel within the Psoas Major Muscle?

Answer 33

Through its fibers

Question 34

Where does the Obturator Nerve emerge from the Psoas Major Muscle?

Answer 34

Its Medial Border

Question 35

Where does the Obturator Nerve travel once it has left the Psoas Major Muscle?

Answer 35

1. Laterally along the Pelvic Wall to the Obturator Foramen 2. Through the Obturator Canal 3. Into the Thigh

Question 36

Where does the Obturator Nerve travel, in relation to the Common Iliac Arteries?

Answer 36

Posteriorly

Question 37

What happens to the Obturator Nerve after it enters the Thigh?

Answer 37

It divides into Branches

Question 38

What are the Branches which the Obturator Nerve divides into, in the Thigh?

Answer 38

1. Anterior Division of the Obturator Nerve | 2. Posterior Division of the Obturator Nerve

Question 39

What does the Anterior Division of the Obturator Nerve descend between?

Answer 39

1. Adductor Longus Muscle | 2. Adductor Brevis Muscle

Question 40

Where does the Anterior Division of the Obturator Nerve travel?

Answer 40

1. Towards the Femoral Artery | 2. Pierces the Fascia Lata

Question 41

What branches arise from the Anterior Division of the Obturator Nerve, before it pierces the Fascia Lata?

Answer 41

1. A Branch to the Adductor Longus Muscle 2. A Branch to the Adductor Brevis Muscle 3. A Branch to the Gracillis Muscle (4. A Branch to the Pectineus Muscle but this is rare)

Question 42

What does the Anterior Division of the Obturator Nerve become after it Pierces the Fascia Lata?

Answer 42

Cutaneous Branch of the Obturator Nerve

Question 43

Where does the Posterior Division of the Obturator Nerve travel?

Answer 43

1. It descends through the Obturator Externus Muscle | 2. Passes Anteriorly to the Adductor Magnus Muscle

Question 44

What branches arise from the Posterior Division of the Obturator Nerve?

Answer 44

Branches to the Adductor Magnus Muscle

Question 45

What is the motor function of the Obturator Nerve?

Answer 45

It innervates the Muscles of the Medial Compartment of the Thigh, except the Hamstring Part of the Adductor Magnus Muscle

Question 46

What are the Muscles of the Medial Compartment of the Thigh, which are innervated by the Obturator Nerve?

Answer 46

1. Adductor Longus Muscle 2. Adductor Brevis Muscle 3. (Adductor Part of the) Adductor Magnus Muscle 4. Gracillis Muscle 5. Obturator Externus Muscle

Question 47

What is the name of the sensory part of the Obturator Nerve?

Answer 47

Cutaneous Branch of the Obturator Nerve

Question 48

Where does the Cutaneous Branch of the Obturator Nerve supply?

Answer 48

Skin of the Middle Part of the Medial Thigh

Question 49

What is the largest Nerve, arising from the Lumbar Plexus?

Answer 49

The Femoral Nerve

Question 50

What is the Segmental (or Nerve Root) Value of the Femoral Nerve?

Answer 50

1. L2 2. L3 3. L4

Question 51

Where does the Femoral Nerve travel in the Abdomen?

Answer 51

1. In the Fibers of the Psoas Major Muscle 2. Passes behind the Iliac Fascia to (approximately) the Mid-point of the Inguinal Ligament 3. It transverses behind the Inguinal Ligament into the Thigh, through the Femoral Triangle

Question 52

Where does the Femoral Nerve exit the Psoas Major Muscle?

Answer 52

At the Lower Part of its Lateral Border

Question 53

What happens to the Femoral Nerve after it enters into the Thigh?

Answer 53

It divides into Branches: 1. Anterior Division of the Femoral Nerve 2. Posterior Division of the Femoral Nerve

Question 54

In the Femoral Triangle, where does the Femoral Nerve travel, in relation to the Femoral Vessels?

Answer 54

Laterally to the Femoral Vessels | Note - it is enclosed within the Femoral Sheath

Question 55

What branches does the Femoral Nerve divide into, in the Femoral Triangle?

Answer 55

Articular Branches to the Hip and Knee Joints

Question 56

What is the Terminal Cutaneous Branch of the Femoral Nerve?

Answer 56

The Saphenous Nerve | Note - this is also known as The Saphenous Branch of the Femoral Nerve