Dermatomes and myotomes Flashcards
What are the two differentiated products of a somite?
- Sclerotome (ventral,gives rise to the vertebrae and ribs)
- Dermatomyotome (dorsal, forms the dermis and muscle tissue)
What is a dermatome?
An area of skin that is supplied by a single spinal nerve
What is a spinal nerve?
A mixed nerve that carries motor, sensory and autonomic signals between the body and spinal cord
What type of fibres do dorsal nerve root transmit and to and where from?
Sensory
- from sensory receptors
- to spinal cord
- affarent root
What type of fibres do ventral nerve root transmit and to and where from?
Motor and autonomic fibres
- from spinal cord
- to effector
- efferent root
How many pairs of spinal nerves are there?
31
Where does the spinal cord run through?
Spinal canal
-from multiple vertebral foramen
Where do spinal nerves leave the spinal canal?
Intervertebral foramina
What is a ramus?
Branching of the spinal nerve after it emerges from the intervertebral foramina
- mixed nerves (sensory, dorsal and autonomic)
- after dorsal and ventral nerve roots
What does the dorsal ramus supply?
Deep muscles and skin of the dorsal trunk
What does the ventral ramus supply?
Muscles and skin of the upper and lower limbs as well as the lateral and ventral trunk
What is a white ramus communicans?
Branch of a spinal nerve that has pre-ganglionic nerves that enters the sympathetic trunk (in the adjacent paravertebral ganglion)
-myelinated nerves
What is a grey ramus communicans?
Branch of a spinal nerve that has post-ganglionic nerves from the sympathetic trunk
-unmyelinated nerves
What are splanchnic nerves?
Post-ganglionic nerves that leaves the sympathetic trunk rather than through grey ramus communicans to a spinal nerve
What is an axial line?
The line between two adjacent dermatomes that are not represented by immediately adjacent spinal levels e.g. in the upper limb between C5 and T1
-Dermatomes can overlap BUT NOT IN AXIAL LINES
What in an axial border?
Cephalic and caudal margins of the limb bud that marks the flexor and extensor compartments (e.g. radial aspect of the upper limb is the pre-axial border)
-Pre-axial or post-axial
What is a myotome?
Group of muscle fibres supplied by a single spinal nerve
What is a motor unit?
A single motor neurone (only one axon) and the skeletal muscle it innervates
What is Hilton’s law?
Nerves supplying the muscles moving the joint also supplies the joint capsule and skin overlying the insertions of these muscles
Define neural level (clinical)?
The lowest level of fully intact sensation and motor function
