Spinal Cord Flashcards
Spinal cord structure
- Runs through the vertebral canal
- foramen magnum –> L1-2
- 31 pairs of spinal nerves
Not uniform in diameter
- cervical enlargement
- lumbar enlargment
what/ where is the Conus medullaris?
tapered inferior end
what is the cauda equina?
lumbar & sacral nerve roots
Development of spinal cord: 8 weeks gestation
- root of first sacral nerve
- at S1
- spinal ganglion
Development of spinal cord: 14 weeks gestation
-conus medullaris forming
Development of spinal cord: Birth
- conus medullaris moves upwards
- filum terminale
Development of spinal cord: Adult
- conus medullaris now located at L1 vertebrae
- extended root of 1st sacral nerve
- extended filum terminale
- attachment of dura mater
Protective structures:
Vertebral column
- solid but felxible protective casing around cord
- intervertebral discs absorb shock
- transmits weight of trunk to lower limbs
- attachment points for ribs and muscles
Ligaments
e. g. ligamentum flavium
- limits potentially damaging movement of the spine
Meninges
-3 protective layers
(dura, arachnoid, pia)
-contains blood supply and CSF
-barrier for neurotoxic substances
CSF Cerebral Spinal Fluid
-nourishing fluid in which the cord is suspended
Segments
- 8 cervical segments (breathing, head and neck movements, heart rate, upper limb movements)
- 12 thoracic (sympathetic tone, trunk stability)
- 5 lumbar (lowe limb movements)
- 5 sacral (bowel and bladder)
- 1 coccygeal segments
Spinal column cross section
- diagram
- dorsal root ganglion
- subdural space
- epidural space
- meninges
Lingamentum Denticulum
- flat membrane formed from PIA MATER
- along midline between dorsal and ventral nerve roots
- laterally to adhere to the arachnoid and dura
- spinal cord is suspended in the middle of the dural sheath
- diagram
Arterial blood supply
- Anterior spinal artery
- Posterior spinal arteries
- Radicular arteries
Venous drainage
- Anterior &posterior median spinal veins in the midline
- ANTEROLATERAL and POSTEROLATERAL paired veins situated near the lines of attachment of the ventral and dorsal roots
- Anterior and Posterior RADICULAR veins
- Internal vertebral venous plexus in the epidural space
- External vertebral venous plexus
Circulation of CSF
- CSF is produced by the choroid plexus of each ventricle
- CSF flows through the ventricle and into the subarachnoid space via the median and lateral apertures. some CSF flows through the central canal of the spinal cord
- CSF flows through the subarachnoid space
- CSF is absorbed into the dural venous sinuses via the arachnoid villi.
Why would a Lumbar puncture be done?
-to obtain CSF from the subarachnoid space
Where would a lumbar puncture be done?
- midline between L3&L4
- between L4 &L5
- inferior to the spinal cord
Expanded subarachnoid space inferior to spinal cord:
Lumbar Cistern
Internal organisation of the spinal cord:
-diagram
Internal organisation of the spinal cord: Cervical
- large ant. grey horn VS post. grey horn
- large diameter (more white matter)
- oval-shaped
Internal organisation of the spinal cord: Thoracic
- small ant. and post. horns
- small diameter (less grey matter)
Internal organisation of the spinal cord: Lumbar
- large ant. and post. grey horns, small lat. grey horn
- reduced white matter
- circular shape
Internal organisation of the spinal cord: Sacral
- proportionally larger grey vs white matter
- small circular shape
Grey matter of spinal cord:
Dorsal (posterior) horn
- sensory (afferent) information
- I-VI (noxious, proprioceptive)
Grey matter of spinal cord: Ventral (anterior) horn
- motor (efferent) information
- VIII-IX
Lateral horn (T1-L2) -VII & X
Tract
neuron bundles within CNS
Nerve
-neuron bundles outside CNS
Descending (motor) tracts: EFFERENT
-these deliver motor instructions from the brain to the spinal cord to the muscles
-Pyramidal/corticospinal tracts
voluntary movements
-Extrapyramidal (indirect pathways)
-all other motor tracts (involuntary)
Motor pathways involve two neurons:
- Upper motor neuron (UMN)
- Lower motor neuron (LMN)
Ascending (Sensory) Tracts: AFFERENT
- posterior column
- spinothalamic
- Spinolimbic/Spinoreticular
- Spinocerebellar
-composed of a 3-neuron chain; 1st order, 2nd order and 3rd order neurons
Posterior column and spinothalamic pathways send impulses to…
the sensory cortex
Spinocerebellar tracts send impulses to…
the cerebellum
-these do not contribute to sensory perception
Spinocerebellar tracts send impulses to…
the cerebellum
-these do not contribute to sensory perception
Ascending (sensory) tracts:
- Pain, temp, and coarse touch cross the midline in the spinal cord
- Fine touch, vibration and proprioception pathways cross the midline in the medulla
- Sensory pathways synapse in the thalamus
- Sensations are perceived in the primary somatic sensory cortex
White matter of spinal cord:
- motor and descending (efferent) pathways
- sensory and ascending (afferent) pathways
- diagram with all labelled tracts
somesthesis
touch
thermosensation
temperature
nociception
pain
proprioception & kinesthesia
position and movement sense
Spinal cord function:
- carry sensory information from the body to the brain
- carry motor information from the brain to the body
- reflexes
Spinal reflex
- pain receptors in skin
- impulse sent to spinal cord via afferent neurons
- impulse sent via axon of efferent neuron
- muscle contracts and withdraws part being stimulated
Spinal nerves
-31 pairs
-C1 emerges above atlas,
C8 emerges below C7 vertebra
-remaining spinal nerves emerge inferior to the corresponding vertebrae
-branching networks of spinal nerves -plexuses
Spinal nerve structure
- dorsal rootlets-dorsal root-spinal nerve-sympathetic ganglion
- ventral rootlets-ventral root-spinal nerve-sympathetic ganglion
Dermatone
=area innervated by afferent in single spinal nerve
Cervical: Upper limb and body
Thoracic: Trunk
Lumbar and sacral: Lower limb
Spinal injury:
Paralysis: Loss of motor function Paraesthesia: Loss of sensation -hemiplegia (right or left) -paraplegia (waist down) -quadriplegia (neck down)
