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ASCENDING AND DESCENDING TRACTS OF SPINAL CORD

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ASCENDING AND DESCENDING TRACTS OF SPINAL CORD Powered By Docstoc
					        By
 Ibrahim AlRashidi
Abdulrahman AlQarni
  Jaser AlHarbi
Mansour aba Hussain




    Supervisor
 Dr.Mustafa Kandil
                OBJECTIVES
• Anatomy of ascending and descending tracts
  of Spinal cord
• Histology of spinal cord
• To list the Function of various ascending and
  descending tracts
• Terminology
• Spinal cord injury
• Management of spinal cord injury
Anatomy
       Spinal Cord Organization
• Gray matter: mostly cell bodies
  – Dendrites & terminals
  – Spinal reflex integrating center
• White matter
  – Bundles of myelinated axons
     • Ascending tracts – sensory
     • Descending tracts – motor
  – Dorsal roots
  – Ventral roots
Spinal Cord Organization
       Location of Tracts inside Cord




          Sensory tracts                                  Motor tracts •
             ---spinothalamic tract    pyramidal tract (corticospinal) –
       ---posterior column                     extrapyramidal tract –
                  ---spinocerebellar                                   –
18-7
              Ascending Tracts
• major ascending
spinal cord tracts
  • posterior white column
  • spinothalamic
     • lateral and anterior
  • spinocerebellar
     • posterior and anterior
           Ascending Tracts

• 1st order Neuron: Dorsal Root Ganglion
 (Spinal Ganglion)
• 2nd order Neuron: Spinal Cord
• 3rd order Neuron: Thalamus PLVNT
Termination: Cerebral Cortex”postcentral
 gyrus”
             Descending Tracts
• Major descending
spinal cord tracts
  • corticospinal
     • lateral and anterior
  • Reticulospinal
     • lateral, anterior and medial
  • Rubrospinal
Spinal Cord Histology : (transverse section)




1- Central Canal : is lined by ependymal cells &
filled with cerebrospinal fluid .


2- Gray matter : is butterfly-shaped. It has a
high density of neuron cell bodies & gliocytes, a
high capillary density, and sparse myelinated
fibers.

3- White matter : is superficial to gray matter.
It is composed of concentrated myelinated fibers,
gliocytes, and low capillary density.
  Gray matter lamination :

Two schemes have evolved for
organizing neuron cell
bodies within gray matter. Either
may be used according to
which works best for a particular
circumstance.

1- Spinal Laminae
spinal gray matter is divided into
ten laminae . The advantage is that
all neurons are included. The
disadvantage is that laminae are
difficult to distinguish.
2- Spinal Nuclei
recognizable clusters of cells are
identified as nuclei [a nucleus is a
profile of a cell column]. The
advantage is that distinct nuclei are
generally detectable; the
disadvantage is that the numerous
neurons outside of distinct
nuclei are not included.
1. posterior horn
2. anterior horn
3. intermediate zone (intermediate
gray)
4. lateral horn
5. posterior funiculus
6. anterior funiculus
7. lateral funiculus
8. Lissauer's tract
9. anterior median fissure
10. posterior median sulcus
11. anterolateral sulcus
12. posterolateral sulcus
13. Posterior intermediate sulcus
     Functions of Ascending Tracts :
1- Gracilis and Cuneatus tracts :
Discriminative touch-
Vibratory sense-
Conscious muscle joint sense (sense of position)-

2- lateral spinothalamic tract :
Pain-
Temperature-

3- anterior spinothalamic tract :
- crude touch
 -pressure
4- spinotectal tract :
Provide afferent information for spinovisual reflexes and
brings movements of the eyes and head toward the source
of the stimulation .


5- spino-olivary tract :
Provides an indirect pathway for further afferent information to
reach the cerebellum .
     Functions of descending Tracts :

1- corticospinal tracts :
Rapid ,skilled,voluntary movements.especially distal ends
of limbs
2- reticulospinal tracts :
Inhibit or faciliate voluntary movement .
3- tectospinal tracts :
Reflex postural movements concerning
Sight
4- rubrospinal tract :
Faciliates activity of extensor muscles and inhibit
flexor muscles
5- olivospinal tract :
May play a role in muscular activity,
But there is doubt that it exists
6- descending autonomic fibers :
are concerned with the control of visceral activity
- Control sympathetic and parasympathetic systems
                         Terminology
• Plegia = complete lesion
• Paresis = some muscle strength is preserved
• Tetraplegia (or quadriplegia)
   – Injury of the cervical spinal cord
   – Patient can usually still move his arms using the segments above the
     injury (e.g., in a C7 injury, the patient can still flex his forearms, using
     the C5 segment)
• Paraplegia
   – Injury of the thoracic or lumbo-sacral cord, or cauda equina
• Hemiplegia
   – Paralysis of one half of the body
   – Usually in brain injuries (e.g., stroke)
Spinal cord injuries
Sensory: how do you determine
           the level?
 High cervical injuries (C3 and above)
• Motor and sensory deficits involve the entire
  arms and legs
     Midcervical injuries (C3-C5)
• Varying degrees of diaphragm dysfunction
• Usually need ventilatory assistance in the
  acute phase
• Shock Due to interruption of the sympathetic
  input from hypothalamus to the
  cardiovascular centers
     Low cervical injuries (C6-T1)
• Usually able to breathe, although occasionally
  cord swelling can lead to temporary C3-C5
  involvement (need mechanical ventilation)
• The level can be determined by physical exam
       Thoracic injuries (T2-L1)
• Paraparesis or paraplegia
Cauda equina injuries (L2 or below)
• Paraparesis or paraplegia
  What is the central cord syndrome?
• Usually occurs with a hyperextension of the
  cervical region
• Cervical spinal cord involvement with arms more
  affected than legs
• May occur with trauma, tumors, infections, etc
• Traumatic lesions tend to improve in 1-2 weeks
• Surgical decompression may be indicated if there
  is spinal stenosis
Brown-Sequard syndrome
                       Management
• Immobilization
   –   Rigid collar
   –   Sandbags and straps
   –   Spine board
   –   Log-roll to turn
• Prevent hypotension
   – Pressors: Dopamine
   – Fluids to replace losses
• Maintain oxygenation
   – O2 per nasal canula
   – If intubation is needed, do NOT move the neck
Gardner-Wells tongs
Soft and hard collars
Minerva vest and halo-vest
             Long term care
• Rehab for maximizing motor function
• Bladder/bowel training
• Psychological and social support
Questions
                  Resources
•   Neuroanatomy Snell
•   Medical physiology Gyuton
•   Physiology lectures dr.Faisal
•   Histology of SC lecture dr.M.Salah

				
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posted:10/8/2011
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