Dermatomes & Myotomes Flashcards
Define dermatome
Area of skin supplied by a single nerve
Describe the embryonic development of dermatomes
Dermatomyotomes (DMT) develop with a specific neural level of spinal cord
Take nerve supply with them from neural tube as spinal (segmental) nerve
Skin and muscle derived from a single dermatomyotome have a common spinal nerve supply
What is axial line
Junction of two dermatomes supplied from discontinuous spinal levels
Describe the anatomical distribution of dermatomes in the upper and lower limbs
See onenote
Define mixed spinal route
Contains both motor and sensory neurons
Describe the difference in content between dorsal and ventral roots
Dorsal (posterior) roots contain afferent/sensory nerve fibres only
Dorsal root ganglion - cell bodies of the sensory neurons from the periphery
Ventral (anterior) roots contain efferent/motor and autonomic nerve fibres only
What are rami and state the rami in a mixed nerve fibre
Mixed spinal nerve divides into rami
Posterior/dorsal ramus - deep muscles and skin of dorsal trunk
Divide into medial and lateral branches
Supply skin of back in segmental manner
Anterior/ventral ramus - muscles and skin of the upper and lower limbs and lateral and ventral trunk
Enters the plexuses
Meningeal branch - re-enters spinal canal through intervertebral foramen
Supplies vertebrae, ligaments, blood vessels and meninges
Rami communicantes - components of the autonomic system
Define myotome
Group of muscles innervated by a single nerve route
Define motor unit
A motor neuron and the skeletal muscles it innervates
Describe Herpes Zoster (shingles)
Viral infection, almost always affects the skin of a single dermatome
Reactivation of varicella zoster virus (chickenpox)
Virus travels through a cutaneous nerve and remains dormant in a dorsal root ganglion after chickenpox
When host is immunosuppressed, VZV reactivates and travels through peripheral nerve to skin of a single dermatome
