dermatomes and myotomes Flashcards
what do somites differentiate into and what do these give rise to?
sclerotome- ventral and gives rise to the vertebrae and ribs
dermatomyotome- dorsal and forms the dermis( via dermatomes) and muscle tissue (via myotomes).
what is a dermatome
area of skin supplied by a single spinal nerve
what does the t10 dermatome supply
umbilicus
what does the T4/T5 dermatome supply
nipples
what does the L1 dermatome supply
groin
what does the C7 dermatome supply
middle finger
what does the c6 dermatome supply
thumb
1st finger
forearm
what is a neurone/ neuron/ nerve cell
electrically excitable cell that receives, processes and transmits information through chemical and electrical signals.
structure of a nerve
enclosed cable like bundle of axons and their supporting cells e.g Schwann cells.
each nerve contains many axons which are each surrounded by a connective tissue called the endoneurium. this consists of an inner sleeve of material called the glycocalyx and a mesh of collagen.
within the endoneurium individual nerve fibres are surrounded by endoneurial fluid. during nerve irritation or injury the amount of endoneurial fluid can increase.
the axons surrounded by endoneurium are bundled together into a fascicle which is wrapped in a connective tissue called perineurium.
the fascicles are then grouped together and surrounded by epineurium.
what are blood vessels in nerve cells called
vasa nervorum
describe a spinal nerve
mixed nerve that carries motor, sensory and autonomic signals between the body and the spinal cord.
the dorsal nerve root transmits sensory fibres from the sensory receptors to the spinal cord so is an afferent root whereas the ventral nerve root is an efferent root and carries the motor and autonomic fibres that are leaving the spinal cord.
what does the spinal cord run through
the vertebral foramen.
multiple vertebral foramina together form the spinal canal.
where does the spinal chord start and finish
starts at the inferior margin of the medulla oblongata and ends at the conus medullaris at L2.
how do the cervical spinal roots emerge from the vertebral body
cervical spinal roots emerge above the corresponding vertebral body with the exception of the 8th cervical spinal root C8 which emerges between the C7 and T1 vertebrae.
how do the corresponding nerve roots exit the thoracic vertebra
exit inferior to the vertebral body.
what happens to the spinal nerve after it emerges through the intervertebral foramen
divides into rami
the dorsal ramus supplies the deep muscles and skin of the dorsal trunk.
the ventral ramus supplies the muscles and skin of the upper and lower limbs and also the lateral and ventral trunk.
each spinal nerve gives off a tiny meningeal branch. what does this do?
re-enters the spinal canal through the intervertebral foramen.
this supplies the vertebrae, ligaments of the vertebral column , blood vessels and meninges.
what happens to the dorsal rami
divide again into medial and lateral branches that supply the skin of the back in a ‘tidy’ segmental manner.
what is an axial line
the junction of two dermatomes supplied from discontinuous spinal levels.
in the upper limb what marks the pre axial border
cephalic vein
in the upper limb what marks the post axial border
basilic vein
in the lower limb what marker the pre-axial and post-axial border ?
the great (long) saphenous veins marks the pre-axial border and the small (short) saphenous vein marks the post axial border.
what is a myotome
A myotome is the group of muscle fibres supplied by a single spinal nerve.
which myotome allows hip flexion
L2
