Dermatomes, Myotomes & Segmental Innervation of the Limbs Flashcards
Each somite develops into?
Sclerotome (ventral) = vertebrae + ribs. Dermatomyotome (dorsal) = dermis (dermatome) + muscle (myotome)
Skin and muscle derived from a single dermatomyotome have what in common?
A common spinal nerve supply
What is a spinal nerve?
Parallel bundle of axons in CT, mixed = motor + sensory, very short, only exist briefly as they pass intervertebral foramen = division between CNS and PNS
Sacral nerve roots exit via?
Sacral foramina
Explain the exiting of all the spinal nerves
C1-C7 exit above corresponding vertebrae, C8 exits between C7 and T1, T1-L5 exit below corresponding vertebrae, S1-S4 exit via sacral foramina, S5-Co1 exit via sacral hiatus
Heading outward, a mixed spinal nerve will divide into?
Rami: anterior (supplies muscles/skin of upper/lower limbs, laterla/ventral trunk) posterior (deep muscles/skin o dorsal trunk),
meningeal branch (supplies vertebrae, ligaments, blood vessels, meninges),
rami communicantes (ANS)
Define dermatome
Area of skin supplied by a single spinal nerve
Describe embryonic development of dermatomes
Each side of neural tube = paired somites = dived to Sclerotome and Dermatomyotome = dermatomyotome dives to dermatome and myotome = as skin + muscles of limbs form they drag their nerve supply with them
Demonstrate the anatomical distribution of the dermatomes of the upper limbs
Demonstrate the anatomical distribution of the dermatomes of the lower limbs
State the segmental sensory innervation of the skin of the upper limb
Define myotome
Group of muscles supplied by a single spinal nerve
Define motor unit
A motor neuron and the skeletal muscle fibres it innervates
State the segmental sensory innervation of the skin of the lower limb
