Spinal Nerves Flashcards
What happens in a lumbar puncture?
Introduction of needle into subarachnoid space
Where is needle inserted in lumbar puncture?
Below level of spinal cord termination - lower risk of spinal cord damage
Uses of lumbar puncture:
CSF for analysis
Administration of drugs - intrathecal
Therapeutic
Specific investigations
Give examples of how lumbar puncture can be used in administration of drugs:
Local anaesthetic
Chemotherapy
Analgesics e.g. painkillers
Give examples of how lumbar puncture can be used in specific investigations:
Myelography and cisternography (in brain)
Contraindictions to lumbar puncture:
Raised intracranial pressure
Abnormal clotting or anticoagulant therapy
Local infection leading to risk of epidural abscess
Indications on body of where to have lumbar puncture:
Feel for iliac crest
Use L4 vertebral spinous process as a guide
Optimal anatomical location for lumbar puncture:
L2/3
L3/4
L4/5
Layers lumbar puncture goes through:
Skin
Subcutaneous tissue
Supraspinous ligament
Interspinous ligament
Ligamentum flavum
Epidural space
Dura mater
Arachnoid mater
Subarachnoid space
Mnemonic for layers lumbar puncture goes through:
SSS I LED AS
What is CSF like?
Clear and colourless fluid
What produces CSF?
Choroid plexus
Ependymal cells in ependymal lining of ventricles of the brain
What also contributes to CSF?
Extracellular fluid of brain parenchyma
What results can we obtain from collecting CSF?
Appearance
Opening pressure
Glucose
Protein
Gram stain and culture
Where are cell bodies of motor neurons found?
Ventral side spinal cord
What carries impulses from CNS to skeletal muscles?
Somatic motor efferents
Route of somatic motor efferents to skeletal muscles:
Leave ventral cord
Pass into corresponding dermatomyotome
How many somites contribute to an individual muscle?
More than one adjacent somite
What does deltoid develop from?
Somites of C5 and C6 cord segments
What is deltoid supplied by?
Nerves arising from segments C5 and C6
When do somites develop?
Day 20-21
What’s a myotome?
Group of muscles innervated by the same peripheral nerve
What can myotome be formed from?
More than one spinal cord segment
Clinical examination of myotome:
Examination of upper + lower limb
Measurement of muscle ‘power’
Isolation of action being tested
Where do sensory neuron cell bodies lie?
In dorsal root ganglia, formed from neural crest cells
What carries sensation from periphery to CNS?
Somatic sensory afferents
E.g. temperature, pain, touch, proprioception
What does each somite give rise to?
A dermatome
What does the dermatome do?
Sends somatic sensory fibres to the segment of spinal cord adjacent to the corresponding somite
What’s a dermatome?
Area of skin innervated by a single spinal segment
What’s the spinal cord divided into?
Segments (related to each somite)
What does each spinal cord segment have?
A pair of spinal nerves
Number of segments in cervical:
8
Number of segments in thoracic:
12
Number of segments in lumbar:
5
Number of segments in sacral:
5
Number of segments in coccygeal:
1
What’s each segment of spinal cord associated with?
Each somite that formed the dermatomyotome
Constituents of spinal nerve: Motor
Motor neurons innervate the associated myotome
Constituents of spinal nerve: Sensory
Sensory neurons innervate the corresponding dermis
Constituents of spinal nerve: Sympathetic
Sympathetic neurons to body wall structures (sweat glands) are only in T1-L2
What is sympathetic outflow found?
Thoracolumbar
Where is cell body of sympathetic neuron found?
Lateral horn (T1-L2)
Where is cell body of motor neuron found?
Anterior/ventral horn
Where does sensory neuron leave?
Dorsal/posterior horn
Where is sensory neuron cell body found?
Dorsal root ganglion
Where do neurons pass through after leaving grey matter?
Intravertebral foramen
Which root does sensory neuron travel through?
Dorsal root
Which root does motor neuron travel through?
Ventral root
Which root does sympathetic neuron travel through?
Ventral root
What does dorsal ramus supply?
Erector spinae muscles
What does ventral ramus supply?
Body wall and limb plexuses
What neurons are in posterior/dorsal ramus?
Sensory and motor
What neurons are in anterior/ventral ramus?
Sensory and Motor
Where are rami comunicantes found?
Near sympathetic ganglion
Where is grey ramis cominicans found?
All levels
Where is white ramus communicans found?
T1-L2
Role of posterior ramus:
Motor to intrinsic back muscles
Sensation to skin over back
Role of anterior ramus:
Motor innervation to chest wall muscles
Sensation to lateral and anterior chest wall
