Dermatomes, Myotomes and Segmental Innervation Flashcards
What are the CNS segments called
Each segment known as a neural level
Where are all the precursors of the nervous system contained during development?
In development the neural tube contains precursors for all cells of the nervous system and somites.
How do the somites differentiate?
At each level a pair of somites differentiate into the sclerotome (cartilaginous structures) on the ventral side and Dermamyotome (dermis and muscles) on the dorsal.
Where to skin and Muscle received there neuronal innervation from?
They each develop at an individual level and so take their nervous innervation with them, so skin and muscle from a common level have the same innervation.
Describe the structure of nerves at each neural level - i.e. whe structure that leave the spinal column at each level?
At each level you have a dorsal root nerve (only contain sensory/afferent fibres) which forms a dorsal root ganglion where it joins the cell bodies of the peripheral fibres and the ventral root (only contains efferent/motor and autonomic fibres).
What makes up the spinal nerve of each level.
Where the dorsal and ventral roots meet makes the spinal nerve of that level - they are very short.
How many spinal nerves there
There are 31 in total
Anatomically where do spinal nerves exist.
They only exist in the intervertebral foramen – boundary between peripheral and central nervous system.
How does the spinal nerve split after leaving the intervertebral foramen?
This spinal nerve splits into dorsal ramus, anterior/ventral ramus (enters the plexuses), meningeal branches (re-enter the canal through intervertebral foramen and the rami that communicate with the Sympathetic chain.
Descirb how the spinal columna changes as it descends down the body
Spinal cord begins below medulla oblongata and continues to the conus medullaris where it stops at T12 then there are many long nerve roots that sprout and continues down the vertebral foramen called the cauda equine.
Relative to their respective vertebrae where does each spinal nerve leave?
C1-C7 exit above their vertebrae, C8 between C7 and T1 vertebrae, T1 to L5 exit below their vertebrae, S1-S4 exit via sacral foramina and S5 and Co1 exit through the sacral hiatus.
Define a Myotome
Myotome – group of muscles supplies by a single nerve root (not a motor unit).
Define a dermatome
Dermatome – section of skin supplied by a single nerve root. Dermatomes have functional overlap across adjacent dermatomes except across the axial line.
How do you define the location of a spinal injury?
The lowest level of FULL sensation.
