Spinal Nerves and their Distribution Flashcards
Why are lumbar punctures preformed?
Sample CSF, measure CSF pressure and to inject treatments such as anaesthetics, antibiotics and chemotherpy.
Where are lumbar punctures preformed? and why there?
Between L3/4 or between L4/5. Preformed here as the spinal cord ends at L1/2, the cauda equina is not likely to be damaged and the subarachnoid space extends to S2.
What are the layers the needle must pass through when preforming a lumbar puncture
Skin
Superficial fascia
Supraspinous ligament
Interspinous ligament
Ligamentum Flavum
Extradural space
Dura Mater
Subarachnoid space
Somites subdivide to form what?
Sclerotome - This forme the vertebral colum, rib cage and occiptial bone.
Dermatomyotomes - Muscles and skin.
Describe the embryological origin of myotomes
The dermatomyotome of each somite gives rise to an individual skeletal muscle with somatic motor nerves leaving the neural tube and passing into the corresponding dermatomyotome to supply to muscle. However adjacent somites can both form an individual muscle.
What is a myotome?
A group of muscles that are innovated by the same spinal nerve.
Describe the embryological development of dermatomes
The dermatomyotome of each somite gives rise to the dermis of the skin. The dermis sends somatic sensory fibres to the spinal cord segment adjacent to its corresponding somite.
Where do somatic sensory neurons develop from?
Neural crest cells
What is a dermatome?
An area of skin supplied by a single spinal nerve
What does each spinal nerve consist of?
- Motor neurons that innervate myotomes
- Sensory neurons that innervate dermatomes
- Sympathetic neurons to structures in the body wall but only from T1-L2
Describe where the dorsal rami of thoracic spinal nerves carry?
- Motor neurons to erector spinae muscles/intrinsic back muscles
- Sensory neurons from the skin of the back and vertebral joints
- Sympathetic Neurons to blood vessels and sweat glands of the skin
Describe where the ventral rami of thoracic spinal nerves carry
- Motor neurons to intercostal muscles
- Sensory neurons from thoracic skin and pleura and vertebral joints
- Sympathetic neurons to blood vessels and sweat glands of the skin
- Form plexuses which give rise to peripheral nerves.
Where will you find grey ramis communicans and white ramus communicans
Grey ramus communicans - at all levels.
White ramus communicans - Only between T1-L2
Describe what the hypaxial muscles and Epaxial muscles form and what they are supplied by.
Hypaxial muscles will form the limbs and body wall muscles. They are supplied by the ventral ramus
Epaxial muscles form the intrinsic back muscles and are supplied by the dorsal ramus
Where are cell bodies of motor neurons located in embryo?
On the ventral side of the neural tube
