Spinal Cord & Derivatives Flashcards
What are the roots of the musculocutaneous nerve?
C5, C6, C7
What are the roots of the axillary nerve?
C5 & C6
What are the roots of the median nerve?
C6, C7, C8, T1
What are the roots of the ulnar nerve?
C8, T1
What are the roots of the radial nerve?
C5, C6, C7, C8, T1
What part of the vertebrae does the spinal cord run through, and how do they leave the vertebrae?
Spinal cord runs through vertebral foramina of spinal vertebrae
Pair of segmental nerves given off at each vertebral level which leave via the intervertebral foramina
note: most spinal nerves issue inferiorly to the corresponding vertebral level (cervical spinal nerves issue superiorly to the corresponding vertebral level)
What is the difference between a neural and spinal level?
Vertebral level - nerve roots exiting immediately below a vertebrae
Neuronal level - nerve root not situated in corresponding vertebral level
e.g. C8 cord (neuronal level) is situated in the C7 vertebrae (no C8 vertebrae - C8 cord goes out through C7-T1)
What is each spinal segment comprised of?
Dorsal root (sensory/afferent) & Ventral root (efferent motor and autonomic)
Join to form dorsal root ganglion which splits into the dorsal ramus and ventral ramus
What is the definition of a dermatome? Why are dermatomes useful anatomically?
DERMATOME = area of skin supplied by sensory nerve fibres from a single spinal nerve (neural level)
note: in reality there is functional overlap between adjacent dermatomes
- reduces probability of skin patches without a natural sensory nerve supply
- damage to a single spinal sensory nerve is less likely to cause anaesthesia (only results if all three successive spinal nerves are damaged)
What is the difference between dermatomes and sensory nerve territories?
DERMATOME = strip of skin supplied by a single spinal nerve
SENSORY NERVE TERRITORY = area of skin related to a peripheral nerve i.e. contains fibres from different spinal nerves
Describe the location of the cervical dermatomes.
C1 = Top of the head C2 = Cheek bones C3 = Anterior neck C4 = Superior aspect of shoulder C5 = Anterior aspect of upper extremity C6 = Anterior side of upper extremity + thumb C7 = Lateral arm and forearm + index and third finger C8 = Medial aspect of upper extremity + ring and 5th finger
Describe the location of the thoracic dermatomes.
T1 = Medial side of forearm + 5th digit T1-T12 = Thorax
Describe the location of the lumbar dermatomes.
L1 = Back + over trochanter + groin L2 = Back + front of thigh and knee L3 = Back + upper buttock + anterior thigh and knee L4 = Medial buttock + anterior thigh and leg L5 = Buttock + thigh and posterior leg
Describe the location of the sacral dermatomes.
S1 = Posterior leg and thigh + buttock S2 = Buttock + thigh and posterior leg S3-S4 = Groin + lower sacrum + genitals + perineum
Describe the movements of the cervical myotomes.
C1-C2 = Neck Flexion C3 = Neck side Flexion C4 = Shoulder shrug C5 = Shoulder abduction C6 = Elbow flexion + wrist extension C7 = Elbow extension + wrist Flexion C8 = Ulnar deviation + thumb extension
