Download Neuro Anatomy Lec.11 د.عبد الجبار الحبي طي The spinal cord

Neuro Anatomy
‫عبد اجلبار احلبيـطي‬.‫د‬
Lec.11
The spinal cord consists of a central core of grey matter
(bodies of neurons) as H-shaped in appearance (2
anterior & 2 posterior horns with grey commissure) & an
outer layer of white matter (nerve fibers) occupied by
tracts.
The cord is divided into R. & L. halves by: -
I-
Anterior median fissure or groove.
II- Posterior median sulcus or septum.
The 2 halves are connected together by a horizontal band
of grey commissure traversed by the central canal.
In transverse section, the grey matter is H-shaped having the
following horns: I-
Anterior horn: -contains lower motor neurons arranged in
3 columns as: -
i-
Medial zone: - which supplies the muscles of the
neck region & trunk (including intercostals &
anterior abdominal wall musculature).
ii-
Central zone: - includes: a- Phrenic nucleus: - in the segments C3 – C5 of
the spinal cord, it gives origin to the phrenic
nerve.
b-
iii-
Accessory nucleus: - in the upper 5 cervical
segments, it gives origin to the spinal
root of accessory nerve.
Lateral zone: - which is responsible for the
formation of brachial & lumbo-sacral plexuses.
II- Posterior horn: - contains sensory nuclei as: -
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I
i-
Substantia gelatinosa: - at the apex of the posterior
horn responsible for pain, temperature & touch
sensation. It is seen along the entire length of the
spinal cord. It gives origin to the lateral spinothalamic tract.
ii- Nucleus proprius:
-in the middle of the horn, just
anterior to substantia gelatinosa. It gives origin to
the anterior spino-thalamic tract responsible for
position & movement (proprioception), two points
discrimination & vibration sensation.
iii- Nucleus dorsalis (clark’s column): -
at the of the posterior
horn from the level of segments C8 – L3 (or L4) it
gives origin to posterior spino-cerebellar tract.
Some cells just medial to the clark’s nuclei gives
origin to anterior spino-cerebellar tract.
iv- Visceral afferent nuclei: -
in the segments T1- L3
resposible for visceral afferent information.
Lateral grey horn: - in the following areas: -
III-
i- T1 – L3 segments: - gives off to the thoraco-lumbar
outflow which is the sympathetic component.
ii- S2 – S4 segments: - gives off to sacral outflow as part
of cranio-sacral outflow (parasympathetic).
Tracts: Means a bundle of nerve fibers having a specific function,
is also known as funiculi
I-
The tracts in the posterior white column:
i-
Gracile tract medially placed.
ii-
Guneate tract laterally placed.
These
tracts
convey
discriminative fine touch.
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proprioceptive
II
sensation
&
They are of first order neurone.
II- Lateral white column tracts:i-Ascending tracts:1-lateral spino thalamic (2nd order venoues).
They cross to the opposite side in the white commissure.
2-posterior spino cerebellar tract (2nd order) carries
proprioceptive sensations to cerebellum,its fibres do not
cross.
3-Anterior spino-cerebellar tract (2nd order).its fibres are
both
crossed
(mainly)
and
uncrossed,carries
proprioceptive to cerebellum.
4-Dorsolateral tract of Lissauer (1st order) arises in the
dorsal root ganglia and carries pain & temperature
sensations.
ii-Descending tracts:1-Lateral cortico-spinal arises from precentral gyrus &
relay on anterior horn cells of s.c.
Its of the crossed fibres.
2-Rubro-spinal tract arises from red nucleus of mid brain
and are crossed fibres.
3-Olivospinal tract arises from olivary nucleus of m.o.
4-Lateral reticulo-apinal tract from the reticular formation
of the brain stem 2,3,4 Belongs to Extrapyramidal system.
5-Descending autonomic tracts arises in the hypothalamus
and relay on the autonomic cells Located in the lateral
grey horn.
Anterior white column tracts:i-Ascending tracts includes:
Anterior spino-thalamic for crude non-discriminative touch
& hight pressure.it crosses to opposite side (2nd order).
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III
ii-Descending tracts as:1-Anterior corticospinal
uncrossed tract.
from
precentral
gyrus.it
is
2-Tecto-spinal tract from tectum of mid brain.it is
uncrossed tract.
3-Vestibulo-spinal tract from vestibular nuclei.
4-Medial reticulospinal tract from reticular formation of
brain stem & of extrapyramidal fibres.
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