1.3.2. The Sacral Plexus Flashcards
What is the Sacral Plexus?
A network of Nerve Fibers, which supplies the Skin and Musculature of the Pelvis and Lower Limb
Where is the Sacral Plexus located?
- It is located on the Surface of the Posterior Pelvic Wall
2. Anterior to the Piriformis Muscle
What forms the Sacral Plexus?
- The Anterior Rami of the of Spinal Nerve S1
- The Anterior Rami of the of Spinal Nerve S2
- The Anterior Rami of the of Spinal Nerve S3
- The Anterior Rami of the of Spinal Nerve S4
(5. The Anterior Rami of the of Spinal Nerve L4 also contributes)
(6. The Anterior Rami of the of Spinal Nerve L5 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 S1-S4?
They intertwine (The Sacral Plexus) and divide into several cords
- Which Lumbar Roots join the Anterior Rami of S1-S4?
2. What do they combine to form?
- a) L4
- b) L5
- Lumbosacral Trunk
Where does the Lumbosacral Trunk travel?
Into the Pelvis
What does the Lumbosacral Trunk join?
The Sacral Plexus
What do the Cords which leave the Sacral Plexus goes on to form?
Major Peripheral Nerves of the Sacral Plexus
What are the Major Peripheral Nerves of the Sacral Plexus?
- Superior Gluteal Nerve
- Inferior Gluteal Nerve
- Sciatic Nerve
- Posterior Femoral Cutaneous Nerve
- Pudendal Nerve
What are the 2 main destinations of the Major Peripheral Nerves of the Sacral Plexus?
- Leaving the Pelvis to the Gluteal Region
2. Remaining in the Pelvis
Which Major Peripheral Nerves of the Sacral Plexus leave the Pelvis, to the Gluteal Region?
- Superior Gluteal Nerve
- Inferior Gluteal Nerve
- Sciatic Nerve
- Posterior Femoral Cutaneous Nerve
Which Major Peripheral Nerves of the Sacral Plexus remain in the Pelvis?
The Pudendal Nerve
How does the Superior Gluteal Nerve leave the Pelvis?
Via the Greater Sciatic Foramen
Where does the Superior Gluteal Nerve enter into the Gluteal Region, in relation to the Piriformis Muscle?
Superiorly
What accompanies the Superior Gluteal Nerve as it enters into the Gluteal Region?
- Superior Gluteal Artery
2. Superior Gluteal Vein
What is the Segmental (or Nerve Root) Value of the Superior Gluteal Nerve?
- L4
- L5
- S1
What is the motor function of the Superior Gluteal Nerve?
- Innervation of the Gluteus Minimus Muscle
- Innervation of the Gluteus Medius Muscle
- Innervation of the Fascia Lata
What is the sensory function of the Superior Gluteal Nerve?
There is none
How does the Inferior Gluteal Nerve leave the Pelvis?
Via the Greater Sciatic Foramen
Where does the Inferior Gluteal Nerve enter into the Gluteal Region, in relation to the Piriformis Muscle?
Inferiorly
What accompanies the Inferior Gluteal Nerve as it enters into the Gluteal Region?
- Inferior Gluteal Artery
2. Inferior Gluteal Vein
What is the Segmental (or Nerve Root) Value of the Inferior Gluteal Nerve?
- L5
- S1
- S2
What is the motor function of the Inferior Gluteal Nerve?
Innervation of the Gluteus Maximus
What is the sensory function of the Inferior Gluteal Nerve?
There is none
What is the significance of the Sciatic Nerve?
- It is the longest Nerve in the body
2. It is a thick, flat band - about 2cm
What is the Segmental (or Nerve Root) Value of the Sciatic Nerve?
- L4
- L5
- S1
- S2
- S3
Where is the Sciatic Nerve derived from?
The Lumbosacral Plexus
How does the Sciatic Nerve leave the Pelvis?
Via the Greater Sciatic Foramen
Where does the Sciatic Nerve enter into the Gluteal Region, in relation to the Piriformis Muscle?
Inferiorly
What direction does the Sciatic Nerve travel, after it enters the Gluteal Region?
Inferolaterally
What does the Sciatic Nerve cross as it travels through the Gluteal Region?
- The Posterior Surface of the Superior Gemelli Muscle
- The Posterior Surface of the Obturator Externus Muscle
- The Posterior Surface of the Inferior Gemelli Muscle
- The Posterior Surface of the Quadratus Femoris Muscle
Where does the Sciatic Nerve enter into the Thigh, in relation to the Long Head of the Bicep Femoris?
Deeply
What branches arise off of the Sciatic Nerve within the Posterior Thigh?
- Branch to the Hamstring Muscle
2. Branch to the Hamstring Part of the Adductor Magnus Muscle
Where does the Sciatic Nerve normally terminate?
At the Apex of the Popliteal Fossa
What happens to the Sciatic Nerve at it terminates?
It bifurcates
What does the Sciatic Nerve bifurcate into?
- Tibial Nerve (sometimes known as the Tibial Branch of the Sciatic Nerve)
- Common Fibular Nerve (sometimes known as the Common Fibular Branch of the Sciatic Nerve)
Note - The Sciatic Nerve can be described as these 2 individual Nerve Bundles
Where does the Sciatic Nerve terminate in 12% of people?
As it leaves the Pelvis
Does the Sciatic Nerve provide motor innervation any Muscles in the Gluteal Region?
No
Where does the Sciatic Nerve directly provide motor innervation for?
- The Posterior Compartment of the Thigh
2. The Hamstring Part of the Adductor Magnus Muscle
What Nerves does the Sciatic Nerve indirectly provide motor innervate via?
Via its 2 Terminal Branches:
- The Tibial Nerve
- The Common Fibular Nerve
What does the Tibial Nerve provide motor innervation for?
- The Muscles of the Posterior Leg
2. Some Intrinsic Muscles of the Foot
What does the Common Fibular Nerve provide motor innervation for?
- Muscles of the Anterior Leg
- Muscles of the Lateral Leg
- Some Intrinsic Muscles of the Foot
What does the Sciatic Nerve provide motor innervation for (in total)?
- Muscles of the Posterior Compartment of the Thigh
- Hamstring Part of the Adductor Magnus Muscle
- All of the Muscles in the Leg
- All of the Muscles of the Foot
Does the Sciatic Nerve provide any direct Cutaneous (sensory) innervation?
No
- Does the Sciatic Nerve provide any indirect Cutaneous (sensory) innervation?
- If so, how?
- Yes
- Via its Terminal Branches:
- a) The Tibial Nerve
- b) The Common Fibular Nerve
What does the Tibial Nerve provide Cutaneous (sensory) innervation for?
- Posterolateral Side of the Leg
- Anterolateral Side of the Leg
- Plantar Surface (Sole) of the Foot
What does the Common Fibular Nerve provide Cutaneous (sensory) innervation for?
- Lateral Aspect of the Leg
2. Dorsal Surface (Roof) of the Foot