Dermatomes, Myotomes, Spinal Nerve Plexus Flashcards
Components of a somite
Dorsal - dermatome
Intermediate - myotome
Ventral - sclerotome
Relationship between nerves, somites and CNS
nerves arise SEGMENTALLY with developing CNS in association with somites
Posterior and Anterior Horn functions
Posterior = sensory Anterior = motor
Where are spinal ganglion
ONLY in the posterior/dorsal root
What muscles types do the Posterior and Anterior rami give rise to respectively
Posterior ramus = epaxial
Anterior ramus = hypaxial
Clinical = what happens if there is a lesion on the dorsal root? What about the ventral root? What about the spinal nerve
Dorsal root = sensory deficit (paresthesia)
Ventral root = motor deficit (muscle weakness)
Spinal nerve = mix of the two
Are roots or rami specific?
Roots are specific to motor and sensory, RAMI are not – they are a mix
Define a dermatome
An area of skin supplied by with afferent nerve fibers by a single Posterior Spinal Root
How are Dermatome Maps and Nerve Maps helpful in the clinical environment?
Dermatome Map = helps identify what SINGLE ROOT SEGMENT is injured or impinged
Nerve Map = helps identify what SINGLE NERVE or SPINAL NERVE PROPER is injured or impinged
Which is more precise: dermatome map or nerve map
nerve map
dermatome maps have a good deal of overlapping
Clinical = why is it important that most muscles are innervated by more than one myotome?
If one goes out, there is no loss of function but there may be a weakening of function
Where are all presynaptic cell bodies form the sympathetic CNS held?
The lateral horn
Where is the lateral horn present?
only in the thoracic vertebrae
What is the difference between parietal and visceral
Parietal = associated with the body wall (smooth muscle, sweat glands, etc.)
Visceral = organs (heart, liver, kidney)
