1.3.1. The Lumbar Plexus Flashcards
What is the Lumbar Plexus?
A network of Nerve Fibers, which supplies the Skin and Musculature of the Lower Limb
Which muscle is the Lumbar Plexus related to?
It is located within the Substance of the Psoas Major
Where is the Lumbar Plexus located, in relation to the Lumbar Vertebrae?
Anterior to the Transverse Process of the Lumbar Vertebrae
What forms the Lumbar Plexus?
- The Anterior Rami of the of Spinal Nerve L1
- The Anterior Rami of the of Spinal Nerve L2
- The Anterior Rami of the of Spinal Nerve L3
- The Anterior Rami of the of Spinal Nerve L4
(5. The Anterior Rami of the of Spinal Nerve T12 also contributes)
How do the Spinal Nerves leave the Spinal Cord?
Via the Intervertebral Foramina of the Vertebral Column
What happens to the Nerves, after they leave the Spinal Cord?
They divide into Anterior and Posterior Fibers (or Rami)
What happens to the Anterior Rami of L1-L4?
They intertwine (The Lumbar Plexus) and divide into several cords, which then go on to form the Major Peripheral Nerves of the Lumbar Plexus
How many Major Peripheral Nerves of the Lumbar Plexus are there?
6
Where do the 6 Peripheral Nerves of the Lower Limb travel?
These descend down the Posterior Abdominal Wall
What are the 6 Major Peripheral Nerves of the Lower Limb?
- Iliohypogastric Nerve
- Ilioinguinal Nerve
- Genitofemoral Nerve
- Lateral Cutaneous Nerve of the Thigh
- Obturator Nerve
- Femoral Nerve
Where does the Iliohypogastric Nerve travel?
- It runs across the Quadratus Lumborum Muscle of the Posterior Abdominal Wall, to the Iliac Crest
- It then perforates the Transverse Abdominis
What happens to the Iliohypogastric Nerve after it perforates the Transverse Abdominis?
It divides into its Terminal Branches
What is the Segmental (or Root) Value of the Iliohypogastric Nerve?
- L1
2. (Contributions from) T12
What is the motor function of the Iliohypogastric Nerve?
- Innervation of the Transverse Abdominis
2. Innervation of the Internal Oblique
What is the sensory function of the Iliohypogastric Nerve?
Innervation of the Posterolateral Gluteal Skin
Is the Ilioinguinal Nerve larger than the Iliohypogastric Nerve?
No
Where does the Ilioinguinal Nerve travel?
- It runs across the Quadratus Lumborum Muscle of the Posterior Abdominal Wall, to the Iliac Crest
- It then perforates the Transverse Abdominis
- It then passes through the Superficial Inguinal Ring
What is the Segmental (or Nerve Root) Value of the Ilioinguinal Nerve?
L1
What is the motor functions of the Ilioinguinal Nerve?
- Innervation of the Transverse Abdominis
2. Innervation of the Internal Oblique
What is the sensory function of the Ilioinguinal Nerve?
- Innervation of the Skin on the Upper Medial Thigh
- a) Innervation of the Skin over the Root of the Penis and Anterior Scrotum
- b) Innervation of the Skin over the Mons Pubis and Labia Majora
What happens to the Genitofemoral Nerve, after it leaves the Psoas Major?
It divides into 2 Branches
What are the 2 Branches the Genitofemoral Nerve?
- Genital Branch of the Genitofemoral Nerve
2. Femoral Branch of the Genitofemoral Nerve
What is the Segmental (or Nerve Root) Value of the Genitofemoral Nerve?
- L1
2. L2
What is the motor function of the Genital Branch of the Genitofemoral Nerve?
Innervation of the Cremasteric Muscle
What is the motor function of the Femoral Branch of the Genitofemoral Nerve?
There is none
What is the sensory function of the Genital Branch of the Genitofemoral Nerve?
- a) Innervation of the Skin over the Anterior Scrotum
1. b) Innervation of the Skin over the Mons Pubis and Labia Majora
What is the sensory function of the Femoral Branch of the Genitofemoral Nerve?
The Skin on the Upper Anterior Thigh
Where does the Lateral Cutaneous Nerve of the Thigh, enter the Thigh?
At the Lateral Aspect of the Ilioinguinal Ligament
What is the Segmental (or Nerve Root) Value of the Lateral Cutaneous Nerve of the Thigh?
- L2
2. L3
What is the motor function of the Lateral Cutaneous Nerve of the Thigh?
There is none
What is the sensory function of the Lateral Cutaneous Nerve of the Thigh?
- Innervation of Anterior Thigh, down to the level of the Knee
- Innervation of Lateral Thigh, down to the level of the Knee
What is the Segmental (or Nerve Root) Value of the Obturator Nerve?
- L2
- L3
- L4
Where does the Obturator Nerve travel within the Psoas Major Muscle?
Through its fibers
Where does the Obturator Nerve emerge from the Psoas Major Muscle?
Its Medial Border
Where does the Obturator Nerve travel once it has left the Psoas Major Muscle?
- Laterally along the Pelvic Wall to the Obturator Foramen
- Through the Obturator Canal
- Into the Thigh
Where does the Obturator Nerve travel, in relation to the Common Iliac Arteries?
Posteriorly
What happens to the Obturator Nerve after it enters the Thigh?
It divides into Branches
What are the Branches which the Obturator Nerve divides into, in the Thigh?
- Anterior Division of the Obturator Nerve
2. Posterior Division of the Obturator Nerve
What does the Anterior Division of the Obturator Nerve descend between?
- Adductor Longus Muscle
2. Adductor Brevis Muscle
Where does the Anterior Division of the Obturator Nerve travel?
- Towards the Femoral Artery
2. Pierces the Fascia Lata
What branches arise from the Anterior Division of the Obturator Nerve, before it pierces the Fascia Lata?
- A Branch to the Adductor Longus Muscle
- A Branch to the Adductor Brevis Muscle
- A Branch to the Gracillis Muscle
(4. A Branch to the Pectineus Muscle but this is rare)
What does the Anterior Division of the Obturator Nerve become after it Pierces the Fascia Lata?
Cutaneous Branch of the Obturator Nerve
Where does the Posterior Division of the Obturator Nerve travel?
- It descends through the Obturator Externus Muscle
2. Passes Anteriorly to the Adductor Magnus Muscle
What branches arise from the Posterior Division of the Obturator Nerve?
Branches to the Adductor Magnus Muscle
What is the motor function of the Obturator Nerve?
It innervates the Muscles of the Medial Compartment of the Thigh, except the Hamstring Part of the Adductor Magnus Muscle
What are the Muscles of the Medial Compartment of the Thigh, which are innervated by the Obturator Nerve?
- Adductor Longus Muscle
- Adductor Brevis Muscle
- (Adductor Part of the) Adductor Magnus Muscle
- Gracillis Muscle
- Obturator Externus Muscle
What is the name of the sensory part of the Obturator Nerve?
Cutaneous Branch of the Obturator Nerve
Where does the Cutaneous Branch of the Obturator Nerve supply?
Skin of the Middle Part of the Medial Thigh
What is the largest Nerve, arising from the Lumbar Plexus?
The Femoral Nerve
What is the Segmental (or Nerve Root) Value of the Femoral Nerve?
- L2
- L3
- L4
Where does the Femoral Nerve travel in the Abdomen?
- In the Fibers of the Psoas Major Muscle
- Passes behind the Iliac Fascia to (approximately) the Mid-point of the Inguinal Ligament
- It transverses behind the Inguinal Ligament into the Thigh, through the Femoral Triangle
Where does the Femoral Nerve exit the Psoas Major Muscle?
At the Lower Part of its Lateral Border
What happens to the Femoral Nerve after it enters into the Thigh?
It divides into Branches:
- Anterior Division of the Femoral Nerve
- Posterior Division of the Femoral Nerve
In the Femoral Triangle, where does the Femoral Nerve travel, in relation to the Femoral Vessels?
Laterally to the Femoral Vessels
Note - it is enclosed within the Femoral Sheath
What branches does the Femoral Nerve divide into, in the Femoral Triangle?
Articular Branches to the Hip and Knee Joints
What is the Terminal Cutaneous Branch of the Femoral Nerve?
The Saphenous Nerve
Note - this is also known as The Saphenous Branch of the Femoral Nerve