Transcript Sympathetically-correlated spinal cord neurons in rats

Spinal Cord Anatomy
Inha University Hospital
Professor Yoon SH
Spinal Cord Anatomy
• Spinal cord is covered by pia, arachnoid,
and dura
• Cord suspended in dural sheath by
denticulate ligament on each side
– Attached along lateral surface of cord midway
between dorsal and ventral roots
Spinal cord anatomy
• Cord is enlarged in cervical (C4-T1) and
lumbosacral regions (L2-S3)
• Cord contains grey matter, white matter
tracts, and central canal
• Central canal lined by ependyma
Spinal cord anatomy
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Gray matter
Dorsal root entry zone
White matter
Vascular anatomy
Cross-section of the spinal cord with
laminae of Rexed
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From G. Paxinos & C. Watson
Lamina of Rexed
• Gray matter of spinal cord divided into
ventral (anterior) and posterior (dorsal)
horns
• Posterior horn contains laminae 1-6
– Lamina 1 gives origin to the pathway relaying
information about pain to the thalamus
– Lamina 2 and 3 (substantia gelatinosa)
functions in regulating afferent input to the
spinal cord.
Lamina of Rexed
– Lamina 4 projects to the lateral cervical
nucleus, the posterior column nuclei, and the
thalamus (spinothalamic tract)
– Lamina 5 and 6 receives proprioceptive input
AND sensory information relayed by lamina 4.
These are the sites of origin of ascending
projections to higher centres.
• From T1 to L3 is Clarke’s column, which is within
lamina 6 and contains projections to the cerebellum
via the dorsal spinocerebellar tract
Lamina of Rexed
• Anterior horn:
• Lamina 9 contains motor neurons supplying
the limbs and lamina 9M contains motor
neurons supplying the trunk and neck. 9M
is medial to 9.
– Is further subdivided into flexor and extensors
(flexors are dorsal) and into distal and proximal
(distal is more lateral).
Lamina of Rexed
• Laminae 7 and 8 contain interneurons involved in
motor control and motor neurons that project to
brain.
– Lamina 8 is highly related to lamina 9M, and
participates in movements of muscles in the head and
neck.
– Lamina 7 is related to lamina 9 and participates in limb
muscle movement
– Lamina 8 and 9M are highly developed in high cervical
and thoracic segments controlling neck and trunk,
whereas laminae 7 and 9 are highly developed in the
spinal enlargements controlling the arms and legs
Lamina of Rexed
• Intermediolateral cell column is present in thoracic
and sacral segments, and is not considered part of
the anterior or posterior horn
• Contains neurons of origin of pre-ganglionic
autonomic fibres
• Lamina 10 surrounds central canal, and contains
neurons that project to the opposite side of the
cord.
White matter
• Divided into dorsal, lateral and ventral
funiculi
• Dorsal funiculus mostly comprised of
ascending fibres whose bodies are located
in dorsal root ganglia
– Fibres are ipsilateral
– Proprioception and fine discrimination (note
that vibration is carried in both dorsal and
lateral funiculi)
White matter – dorsal funiculus
• Fasciculus gracilis medial to fasciculus cuneatus
• F. gracilis from lower limbs and cuneatus from
upper limbs
• Note that lowest segmental innervation is most
medial in gracilis and highest innervation is most
lateral in cuneatus
• Nucleus gracilis and cuneatus in medulla
• There are descending fibres in dorsal funiculus
which modify sensory input to the cord
White matter – lateral funiculus
• Dorsolateral and lateral parts (fasciculi)
• Dorsolateral contains lateral corticospinal tract
(axons from contralateral frontal and parietal
lobes); frontal fibres end in ventral horn
– Lower limbs are lateral in tract and head is medial
– Distal muscles are posterior to proximal muscles
• Rubrospinal tract (from contralateral red nucleus)
is rudimentary in humans; involved in increasing
flexor tone
Lateral funiculus
• Raphespinal tract in dorsal part of lateral
funiculus; modifies painful stimuli from
dorsal horn; fibres may begin in reticular
formation of medulla
• Hypothalamospinal tract arises from
paraventricular nucleus of hypothalamus
and end in pre-ganglionic autonomic
segments T1-L3 and S2-S4
Lateral funiculus
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spinocervical tract ascends and terminates in
lateral cervical nucleus, which is rudimentary in
humans (significance is unknown)
• Dorsal spinocerebellar tract is present above L3;
arises from Clarkes column and terminates in
ipsilateral cerebellum; forms part of pathway of
conscious proprioception from lower limb
Lateral funiculus
• Ventrolateral fasciculus
• Spinothalamic tract has its nuclei in lamina 4,5,6
mostly.
– Axons cross midline in ventral white commissure and
traverse the ventral horn
– End in thalamus
– Collateral branches to reticular formation
– Pain and thermal sensations
– Fibres from lower limb are most superficial and from
upper limb are deepest
Lateral funiculus
• Ventral spinocerebellar tract arises from
dorsal horn and border cells of ventral horn
of lumbosacral cord
• Crossed fibres
• Ascends to midbrain, enters superior
cerebellar peduncle, and decussates again,
and enters cerebellar cortex
• Concerned with proprioception
Lateral funiculus
• Spinotectal tract fibres from same part as
spinothalamic tract end in superior
colliculus and reticular formation (fibres are
crossed
• Spinoreticular tract originates in laminae 48 ends in reticular formation; is important in
perception of pain and other modalities
originating in internal organs
Lateral funiculus
• Spino-olivary tract has uncertain role in
humans
• Ventrolateral fasciculus also contains
descending medullary reticulospinal tract,
which controls motor activities that do not
require conscious effort
Ventral funiculus
• Ventral corticospinal tract contains
uncrossed fibres
• Vestibulospinal tract is uncrossed pathway
from the lateral vestibular nucleus of
medulla; axons terminate in lamina 8
– Mediates reflexes of equilibrium
Ventral funiculus
• Pontine reticulospinal tract
• Medial longitudinal fasciculus (only in cord
to upper cervical levels) is involved in
movements of head required for equilibrium
• Tectospinal tract from contralateral
superior colliculus
Fasciculus proprius
• Present in all funiculi immediately adjacent
to gray matter
• Contains propriospinal fibres which connect
different segmental levels of gray matter
• Ascend and descend variable lengths and
provide functional equivalent of
interneurons
Dorsal root entry zone
• Each dorsal root branches into 6-8 rootlets
• Axons segregated into two divisions within
each rootlet: lateral and medial
• Lateral contains unmyelinated (type C)
fibres and enters dorsolateral tract of
Lissauer
• Medial contains larger, myelinated axons,
and enter white matter medial to dorsal horn
Vascular anatomy - Arterial
• Cord is supplied by multiple radicular arteries,
which form the anterior and posterior spinal artery
• Radicular arteries arise from adjacent arteries at
each vertebral segment
– Pass through intervertebral foramina to supply nerve
roots, but most do not reach the cord
• Larger radicular arteries which also supply cord
are called radiculomedullary arteries
Vascular anatomy - arterial
• Anterior spinal artery originates in upper
cervical region, from anterior spinal
branches of vertebral artery.
• 6-10 anterior radicular arteries contribute to
it throughout its length.
• Supplies anterior two thirds of cord, via
central branches and penetrating branches
of pial plexus
Vascular anatomy – arterial
territories
• Cervical and first two thoracic segments of cord
are supplied by radicular a. that arise from
subclavian a. or branches thereof
– High degree of variability
• mid-dorsal region of cord (T3-T7) is supplied
from radicular a. accompanying T4 or T5 root
• T8 to conus supplied by artery of Adamkiewicz
Vascular anatomy - Adamkiewicz
• Arises from left sided lumbar (segmental) artery in
80%
• 85% reaches cord between T9-L2; 15% between
T3-T8 (in these cases it is supplemented by a
radicular artery arising more inferiorly)
• Has large anterior and small posterior branch
– Anterior branch ascends, then gives off a small
ascending branch and larger descending branch
– Descending branch goes inferior (to conus) and makes
an anastomotic loop with posterior spinal a.
Vascular anatomy – arterial
• Cauda equina also supplied by branches
from lumbar, iliolumbar, and lateral and
median sacral a.
Vascular anatomy – posterior
spinal artery
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Paired arteries
Run along posterolateral cord
Sometimes discontinuous
Originates from verterbral artery
Has contribution from 10-23 posterior
radicular a.
• Supplies posterior one third of cord
Vascular anatomy
• Anterior spinal a. gives off central branches and
branches to pial plexus
• Central branches run in anterior median fissure
and supply central cord
• Pial plexus is formed from both anterior and
posterior spinal a.
– Give penetrating branches which supply outer cord
• Some overlap between supply of central and pial
branches
Vascular anatomy - venous
• Internal and external vertebral venous
plexuses
• Form rings around each vertebra
• Freely anastomose with each other
Vascular anatomy - venous
• External plexus has anterior part (anterior to
vertebral body) and posterior part (over
posterior elements including laminae and
spinous processes)
• Anterior and posterior parts freely
anastomose
Vascular anatomy - venous
• Internal plexus: anterior part is on each side
of PLL, posterior to vertebral body;
posterior part is interior to ligamentum
flavum
• Vertebral body drained by basivertebral
veins which enter anterior external plexus
Vascular anatomy - venous
• Veins of cord mirror related arteries in distribution
• Venules drain into anterior and posterior veins,
which drain into two median longitudinal veins,
and into anterolateral and posterolateral
longitudinal veins lying adjacent to the nerve roots
• Radicular veins join branches from internal plexus
forming intervertebral veins (have valves), which
exit intervertebral foramina and join their
respective segmental veins