Development of the somatic nervous system a d dermatomes/myotomes Flashcards
Sensory:
Neural crest cells develop into dorsal root ganglia
Central process to dorsal neural tube and peripheral process to the somite
motor
Motor neuron nuclei in the ventral neural tube extend a peripheral process to the somite
- motor neurons differentiate into multipolar neurons
As the cells of the somites migrate
the peripheral processes of the neurons follow them.
The segmental relationship
between the nervous & musculoskeletal systems & the dermis is preserved! - established at embryo
somatotopy
somatotopic arrangement of fibres
dermatome
area of skin innervated by the sensory neurons from a single spinal segment (dorsal root)
myotome
collection of muscle fibres innervated by the motor neurons from a single spinal segment (ventral root)
spinal cord / spinal nerve lesion.
indicated by sensory changes in a dermatomal distribution &/or motor changes in a myotome distribution
C6 DERMATOME
The dermis of the skin in this region
develops from the mesoderm
originally associated with the C6 neural crest cells
dermatomes in LL
spiral inwards and go around
* rotation of the limbs “during the 6th to 8th weeks causes the mature dermatomes to spiral”
Segmental organisation: myotomes
•motor neuron nuclei are arranged in long vertical columns of grey matter in the ventral spinal cord
•their axons exit the spinal cord via multiple ventral nerve roots
* Each spinal nerve root innervates more than 1 muscle
• Most muscles are innervated by more than 1 spinal segment
C1&2
neck flx and ext
C3
neck lateral flx
C4
shoulder shrug
C5
elbow flexors (biceps, brachialis)
