Flashcards in MSK - Dermatomes And Myotomes Deck (28)
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1
What is a neural level?
A segment of the central nervous system
2
What does the 'somite' differentiate into in the fourth week of embryological development?
- the sclerotome (ventral) which forms vertebrae and ribs
- the dermatomyotome (dorsal) which forms dermis and muscle
3
What do skin and muscle derived from a single dermatomyotome share?
A common spinal nerve supply
4
What do the 'roots' connect in the spine?
They connect each spinal nerve to a segment of spinal cord
5
What do dorsal (posterior) roots contain?
Afferent/sensory nerve fibres
6
What do ventral (anterior) roots contain?
Efferent/motor and autonomic nerve fibres
7
What are spinal nerves?
Parallel bundles of axons encased in connective tissue, which exist only briefly as they pass through the intervertebral foramen
8
How many spinal nerves are there?
31 pairs, which are numbered according to the level of vertebral column that they emerge from
9
What's the difference between an epineurium, a perineurium and an endoneurium?
Epineurium covers the entire nerve, perineurium surrounds each fascicle and endoneurium is around each axon
10
What is a vertebral foramen?
A gap in the vertebra which the spinal cord runs through. Multiple vertebral foramina form the spinal canal.
11
What is a external segment?
The name given to a single vertebra, which differentiates from a sclerotome
12
Where does the spinal cord run?
Starts at inferior margin of medulla oblongata, ends as conus medullaris at L2
13
True or false - all spinal cord segments are perfectly aligned with their corresponding vertebrae?
False - long roots from inferior segments descend in cauda equina to exit at their respective foramina
14
Where does the first pair of spinal nerves emerge?
Between occipital bone and atlas
15
Where do C1-C7 emerge?
Above the corresponding vertebrae
16
Where does the spinal nerve (C8) exit?
Between vertebrae C7 and T1
17
Where do S1-S4 exit?
Via four pairs of sacral foramina
18
What are 'rami'?
These are what the spinal nerve divides to form
19
What does the posterior/dorsal ramus innervate?
Deep muscles and skin of the dorsal trunk
20
What does the anterior/ventral ramus innervate?
Muscles and skin of the upper and lower limbs and lateral and ventral trunk
21
What is a myotome?
A group of muscles supplied by a single spinal nerve (or spinal nerve root)
22
What is a dermatome?
An area of skin supplied by a single spinal nerve or spinal nerve root
23
What is a motor unit?
A motor neuron and the skeletal muscle fibres it innervates
24
What's the difference between a myotome and a motor unit?
1 spinal nerve contains the neurons of many motor units, but supplies one myotome
25
What is an axial line?
A junction of two dermatomes supplied from discontinuous spinal levels
26
What do axial lines on the limbs mark?
The centre of either the ventral or dorsal compartments of the limb
27
What are peripheral nerve territories?
Areas of skin supplied by the peripheral nerves eg. branches of the lumbar plexus
28
