Spinal Cord Flashcards
What are the anterior boundaries of the vertebral canal?
vertebral bodies
intervertebral discs
posterior longitudinal ligament
What are the lateral boundaries of the vertebral canal?
Pedicles - notches
intervertebral foramina
What are the posterior boundaries of the vertebral canal?
laminae
facet (zygapophyseal) joint
ligamentum flavum
spinous processes
The spinal cord is protected by?
Vertebrae
Ligaments
Meninges
CFS cushioning
How many spinal nerves are there?
31 pairs
8 Cervical nerves C1 – C8
12 Thoracic T1 –T12
5 Lumbar L1 – L5
5 Sacral S1 – S5
1 Coccygeal Co
Spinal nerves consist of?
- axons of sensory neurones from an area of skin (dermatome)
- axons of motor neurones to a group of muscles that share a function (myotome)
- axons of sympathetic neurones to structures in the body wall that control body temperature
Where do you get a sample of CSF?
can be sampled by inserting a needle into subarachnoid space below the Conus Medullaris
Compare the course of the spinal cord in adults to that of neonates?
Begins at the foramen magnum of the skull as the continuation of the brain stem
In adults
foramen magnum > disc between L1/L2
> In adults the spinal cord occupies the upper 2/3rds of the canal
In neonates
foramen magnum > approximately L3
Ends as the filum terminale attached to the sacral vertebral bodies
Where are the spinal cord enlargements?
- Cervical expansion
- between C5 and T1
- due to the brachial plexus - Lumbosacral expansion
- L1 and S3
- due to the lumbar plexus - Conus medullaris
- most inferior part of the cord before it narrows to form the filum terminale
What is the lumbar cistern?
Subarachnoid space caudal to the end of the spinal cord
> CSF
> Roots of lumbar and sacral nerves
Name and describe the structural components of the spinal cord?
- Anterior/Ventral median fissure
- Deep
- CT of pia mater
- Anterior spinal artery and its branches - Posterior/Dorsal median fissure
- Shallow midline fissure - Central canal
- CSF very small
- Lined by ependyma cells
- In brain this space is expanded to form ventricles
Slight grooves where the nerve rootlets arise form the cord
What is the white matter of the spinal cord?
Tracts of axons
Myelinated axons
What is the grey matter of the spinal cord?
nerve cell bodies
What is the Bell-Magendie Law?
Afferent fibers enter spinal cord through dorsal root spinal verves
Motor and other efferent fibers leave through ventral roots
What are motor neurons?
- Excited or inhibited by impulses
- Impulse originate at various levels of brain
- Medulla to cerebral cortex
Describe the white matter of the spinal cord?
- Myelinated – white
- Have nerve fibres, neuroglia, blood vessels
- Divided into 3 faniculi/columns
1. Anterior/Ventral White Faniculus
2. Lateral White Faniculus
3. Posterior/Dorsal White Faniculus
> Gracile Fasciculus : Present throughout the length of the cord
> Cuneate Fasciculus : Above mid-thoracic level - Axons decussate in ventral white commissure
- Dorsolateral tract/Tract of Lissauer
> Occupies space between apex of dorsal horn and surface of cord
Describe the gray matter of the spinal cord?
- Gray mater H-shaped
- Central gray matter indicate the number of neurons
- Anterior/Ventral Gray Horn
- Posterior/Dorsal Gray Horn
- Intermediate zone joining two horns
- Lateral Gray Horn (in thoracic and lumbar regions)
- Commissure – joining two sides
Name the 3 types of neurons in gray matter?
- Motor cells
- Are in ventral horn
- Supply the skeletal musculature - Tract cells
- Mainly located in dorsal horn
- Constitute ascending fasciculi of white matter - Interneurons
- Cells involved in local circuit
What are the laminae of Rexed?
- Cells of same type cluster in groups in gray matter
- Looks like layers (esp. Dorsal Horn) but occur in columns
- 10 layers recognized known as Laminae of Rexed
Describe lamina I of the spinal cord?
Tip of the dorsal horn
Cells respond to noxious or thermal stimuli
Sends information to the brain by contralateral spinothalamic tract
Corresponds to marginal zone
Describe lamina II of the spinal cord?
Sensation of noxious and non-noxious stimuli
Modulating sensory input to contribute to the brain’s interpretation of incoming signals as painful, or not.
Sends information to Lamina III and IV
Corresponds to Substantia Gelatinosa
Describe lamina II of the spinal cord?
Sensation of noxious and non-noxious stimuli
Modulating sensory input to contribute to the brain’s interpretation of incoming signals as painful, or not.
Sends information to Lamina III and IV
Corresponds to Substantia Gelatinosa
Describe lamina III of the spinal cord?
Involved in proprioception and sensation of light touch.
Cells in this layer connects with cells in layers IV, V and VI.
Partially corresponds to nucleus proprius
Describe lamina IV of the spinal cord?
Non-noxious sensory information relay and processing.
Cells connect with those in lamina II
Partially corresponds to Nucleus Proprius
Describe lamina V of the spinal cord?
Relays sensory, including nociceptive (potentially painful), informationto the brain via the contralateral and spinothalamic tracts
Receives descending information from the brain via the corticospinal and rubrospinal tracts.
Describe lamina VI of the spinal cord?
Contains many small interneurons
Involved in spinal reflexes
Receives sensory information from muscle spindles (involved in proprioception).
Sends information to the brain via ipsilateral spinocerebellar pathways
Describe lamina VII of the spinal cord?
Large, heterogenous zone that varies through the length of the spinal cord.
Receives information from Lamina II to VI, and from viscera
Relays motor information to the viscera
Gives rise to cells involved in the autonomic system
Dorsal nucleus of Clarke is part of Lamina VII
Describe lamina VIII of the spinal cord?
Varies depending on spinal cord level, but is most prominent in cervical and lumbar enlargements
Cells are involved in modulating motor output to skeletal muscle
Describe lamina IX of the spinal cord?
Size and shape varies between spinal cord levels
Distinct groups of motor neurons that innervate skeletal muscle
Describe the lamina X of the spinal cord?
Surrounds the central canal – the grey commissure
Axons decussate (cross over) from one side of the spinal cord to the other
Describe the Marginal zone (MZ, posterior marginalis)?
At the tip of the dorsal horn
Relay pain and temperature sensation to the brain
Describe the substantia gelatinosa of the spinal cord?
At the top of the dorsal horn
Relay pain, temperature and light touch sensation to the brain
Describe the nucleus proprius nuclei of the spinal cord?
In the ‘neck’ of the dorsal horn
Relay mechanical and temperature sensation to the brain.
Describe the dorsal nucleus of Clarke nuclei of the spinal cord?
Most dorso-medial nuclei
Relay unconscious proprioceptive information to the brain
Only found in spinal segments C8 to L3.
Describe the Interomediolateral nucleus (IMN) nuclei of the spinal cord?
In the intermediate column and lateral horn
Relay sensory information from viscera to the brain, and autonomic signals from the brain to the visceral organs
Describe the Lateral motor neurons and medial motor neurons (MNs) of the spinal cord?
In the ventral horn.
Composed of motor neurons that innervate visceral and skeletal muscles
Compare white matter and gray matter in the spinal cords?
- Same pattern but regional differences are seen
- White matter increases in caudal to rostral direction
> Fibers are added to ascending tracts
> Fibers leave descending tracts to terminate in gray matter - Gray matter correspond to spinal enlargements and lateral horn
- In thoracic upper lumbar presence of lateral horn of gray matter
Describe white matter long tracts?
- White matter divided into longitudinally aligned faniculi
- Each faniculi contain ascending and descending fibers
- Position of each tract determined by
> Clinical and pathological studies
> Animal studies - Some tracts their precise location is still not well understood
- Serve to join the spinal cord to the brain
What are the meninges?
Three membranes that:
Surround and protect spinal cord
Suspend the brain and spinal cord
Line the cranium and vertebral canal
Describe the dura matter of the spinal cord?
- Very thick protective layer
- Continuous with Dura mater of the brain
- Forms a tube extending from level of 2nd sacral vertebrae to foramen magnun
- But is separated from the bones of the vertebral canal by a layer of fat (extradural fat)
- Ends at lower border of S2
> Fuses with the filum terminale - Covers the roots of the spinal nerves as they pass through the intervertebral foramina
Describe the arachnoid matter of the spinal cord?
- Lies inside the dura
- Subarachnoid space between arachnoid and pia mater
> Continuous with space around the brain
> Ends at lower border of S2
> Contains CSF
> Contains blood vessels supported by a ‘cobweb’ of fibres
> Contains the cauda equina
Describe the pia mater of the spinal cord?
- Thin, vascular layer closely adheres to the surface of the cord and brain
- In the vertebral canal, triangular extensions of pia (denticulate ligaments) are attached to the dura and so suspend the cord in the space
- Attach at 21 points
- Lateral wall serrated
- Attach midway between dorsal and ventral roots
Describe the epidural space of the spinal cord?
- Intervenes between dura and wall of vertebrae
- Filled with fatty tissue that contains venous plexus
- Caudal to second sacral vertebra contains roots of most caudal spinal nerves
Describe the spinal cord blood supply?
- Longitudinal vessels
- Lie on the surface of the cord in the mid line
- Spinal arteries - branches of the vertebral arteries - Segmental branches from the aorta
- Enter through the intervertebral foramina
- Cervical (vertebral arteries)
- Thoracic (intercostal arteries)
- Lumbar (lumbar arteries
Describe the anterior spinal artery?
Anterior spinal artery
• Formed by the union of 2 arteries
• From vertebral artery
• Supply anterior ⅔ of spinal cord
Describe the posterior spinal arteries?
Posterior spinal arteries
• Arise from vertebral artery or posterior inferior cerebellar arteries (PICA)
• Descend close to the posterior roots
• Supply posterior ⅓ of spinal cord
Describe the venous drainage of the spinal cord?
- longitudinal channels on surface of cord
- no valves
- internal vertebral venous plexus
> in extradural fat - vertebral venous plexus
> drains the medullary cavity of the vertebral body
> connected to segmental veins (e.g. lumbar and azygos veins) - venous connections allow the metastatic spread of tumours to vertebral bodies e.g. from breast and prostate
