Part 1 - Dermatomes And Myotomes Flashcards
Anatomically, what is a neural segment known as?
A neural level
What day of embryological development does the neural plate form (primitive neural tissue?
18 days
What day of embryological development does the neural plate begin to invaginate to form the neural groove?
21 days
What week of embryological development does the neural groove close/ fuse together to form the neural tube?
4th week (22days ….)
From where does the neural groove start to close and which direction does this closing happen?
Starts centrally
Then the closing happens outwards in the caudal and cephalic direction
When do paired somites form in embryological development?
4th week
Where are the paired somites located?
Either side of the neural tube
In embryological development, which structure contains the precursor cells of the nervous system?
Neural tube
What do the somites differentiate into?
Sclerotome
Dermatomyotome
Which part of the somite differentiates into the sclerotome?
The ventral side
Which part of the somite differentiates into the dermatomyotome?
Dorsal side
What does the dermatomyotome differentiate into?
Dermis (Skin) and muscle
What does the sclerotome differentiate into?
Vertebrae
Ribs
What does each segment of the spinal cord have?
A spinal nerve
What do all Dermatomyotome develop in association with?
A specific neural level of the spinal cord
As a Dermatomyotome migrates to its area, what does it take with it from the neural tube?
Spinal nerve
What is important to know about the nerve supply of the skin and muscle derived from a single dermatomyotome?
They have a common spinal nerve supply
What is the connective tissue called that surrounds a single axon?
Endoneurium
What are many axons running in parallel called?
Fascicle
What is the connective tissue called that surrounds a fascicle?
Perineurium
What is a collection of fascicles called?
The nerve
What is the connective tissue called that surrounds a nerve?
Epineurium
What are the blood vessels called that are found within the Epineurium of the nerve?
Vasa nervorum
What are spinal nerve roots?
They connect each spinal nerve to a segment of spinal cord
What type of nerve fibres/axons do dorsal/posterior roots contain?
Sensory or afferent fibres
What type of nerve fibres do ventral/anterior roots contain?
Motor/efferent and Autonomic fibres
What is a dorsal root ganglion?
A group of cell bodies of sensory neurons from the periphery just before the spinal cord is reached
What makes up a spinal nerve?
Both Dorsal (sensory) and Ventral (motor) roots together
Where do you find spinal nerves?
The intervertebral foramen
Where marks the division between the CNS and PNS?
Spinal nerves in the Intervertebral foramina
How is a vertebra formed from somites?
The sclerotomes from 2 adjacent somites both contribute to the formation of 1 vertebra
What do you call the space created by multiple vertebral foramina?
Spinal Canal
What passes through the spinal canal/multiple vertebral foramina?
Spinal cord
Through what structure do the spinal nerves leave the spinal canal?
Intervertebral Foramen
Where does the spinal cord start?
Inferior margin of medulla oblongata
Where does the spinal cord end?
L1 - L2
Called Conus medullaris
What happens at the end of the spinal cord (Conus medullaris)?
Long spinal roots come out from the conus medullaris and descend down until they exit at their respective foramina
What is the group of long descending roots from the conus medullaris called?
Cauda equina
Do the C1 - C7 spinal nerves exit their intervertebral foramina above or below their corresponding vertebrae?
ABOVE THEIR VERTEBRAE
How many cervical vertebrae are their?
7
How many cervical nerves are their?
8
Where does the spinal nerve C8 exit the spinal canal?
Between C7 and T1
Under C7 but above T1
Do the spinal nerves T1 - L5 exit ABOVE or BELOW their corresponding vertebrae?
BELOW THIER VERTEBRAE
What is special about the structure of the sacral vertebrae (S1 - S4)?
They are fused together forming the Sacral bone
What are the foramina called by which the S1 - S4 spinal nerves exit through?
Sacral foramina
What structure does the S5 and Co1 spinal nerves exit via?
Sacral hiatus
What happens once a spinal nerve exits the an intervertebral foramen?
Branches into 2 ram II
What are the 2 rami that form when the spinal nerve exits the intervertebral Foramen?
Dorsal/posterior ramus
Ventral/anterior ramus
What do the dorsal/posterior rami supply?
Deep muscles and skin of the dorsal (posterior trunk, so the back)
What do the ventral/anterior rami supply?
Muscles and skin of UPPER and LOWER LIMBS and LATERAL and VENTRAL TRUNK
What is a meningeal branch?
A brach off of the spinal nerve which renters the spinal canal via the intervertebral Foramen
What do the meningeal branches supply?
Vertebrae
Ligaments
Blood vessels
Meninges
What are the 2 types of Rami communicantes?
White Rami communicantes
Grey Rami communicantes
What does the white rami communicantes contain?
Sympathetic pre ganglioninc MYELINATED fibres
They come off between T1 and L2
FIbres enter sympathetic chain and synapse
What do the Gray rami communicantes contain?
Post ganglionic fibres supplying the periphery
Come off at all levels
What do the Dorsal Rami of spinal nerves supply?
Muscle and skin of posterior trunk
What do the ventral rami of the spinal nerves supply?
Anterior trunk
Lateral trunk
Upper limbs
Lower limbs
How do the dorsal/posterior rami further divide?
Medial branch
Lateral branch
Compare the supply of the dorsal/posterior rami to the skin to the ventral/anterior rami?
Dorsal = Supply skin to oback in tidy segmental manner
Ventral = Trunk is segmental, complicated for limbs due to plexuses
What is a Dermatome?
An area of skin supplied by a single spinal nerve
What is a plexus?
Network of intersecting nerves arising from the anterior/ventral rami
What nerves make up the brachial plexus?
C5 - T1
What does the brachial plexus supply?
Upper limbs
What spinal nerves make up the Lumbo-sacral plexus?
L1 - S5
What does the lumbo-sacral plexus supply?
Lower limbs
On the Dermatome map, what is the next Dermatome in the trunk following C4?
T2
What landmark can be used to find T10 Dermatome?
Umbilicus (belly button)
What landmark is roughly used for the T4, T5 Dermatome?
Nipples
Where is the L1 Dermatome?
Groin
