Post on 03-Jun-2018
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The spinal cord begin as a
continuation
of the medulla oblongata.
In adults, 42-45cm in long
Extend from the foramen magnum
in theoccipital bone to the level of the
L1 or L2(in adult)
In newborn infants, it extends to
the third or fourth lumbar vertebra
Elongation of the spinal cord stops
around age 4 or 5, but growthof the vertebral column continues
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Enlarged in two regions :
1. Cervical enlargment
(C4-T1 segment ofthe spinal cord)
2. Lumbosacral enlargment
(T11-S1 segment of
the spinal cord)
The spinal cord occupies
only the superiortwo thirds of the
vertebral canal
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The conus medullaris is tapering inferior end,
terminate as high as T12 vertebrae or
as low as L3 vertebrae
Cauda equina is bundle ofspinal nerve roots
arising from the lumbosacral enlargment & the
medullary cone, caudal to the termination
of the spinal cord resembles a horses tail
filum terminale:
-arising from the tip of the conus medullaris,
descend among the spinal roots in the cauda equina
-an anchor for the inferior end of spinal cord
and the spinal meninges
Two parts of filum terminale :1. Pial part / internal terminal filum
2. Dural part/external terminal filum
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Vertebral
column
Vertebralligament
Meninges
CSF
Denticulateligament
Cushion of fat &
connective tissuelocated in epidural space
Denticulate ligament :
Triangular-shaped membranous extensions of
the pia mater
suspend the spinal cord in the middle of its duralsheath
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Consist of dura mater, arachnoidmater & pia mater
Spinal dura mater :
Composed mainly of tough
fibrous with some elastic tissue, is
the outermost covering
membrane of the spinal cord
The spinal dura forms the spinal
dural sac, a long tubular sheath
within the vertebral canal.
The sac is anchored inferiorly to
the coccyx by the filum terminale
The spinal dura mater isseparated from the periosteum-
covered bone and the ligaments
that form the walls of the vertebral
canal by the epidural space.
Content of epidural space :
Fat, internal vertebral venous
plexuses, root of spinal nerves
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Spinal arachnoid mater :
is a delicate, avascular membrane composed of fibrous and elastic tissue
Their apposition is the dura-arachnoid interface , often erroneously referred toas the subdural space.
The spinal arachnoid is separated from the pia mater on the surface of the
spinal cord by the subarachnoid space.
Content of subarachnoid space :CSF; radicular, segmental, medullary, andspinal arteries; veins; arachnoid trabeculae.
The enlargement of the subarachnoid space in the dural sac, caudal to the
conus medullaris and containing CSF and the cauda equina, is the lumbar
cistern. It extends from the L2 vertebra to the second segment of the sacrum.
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L2-S2
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Spinal pia mater :
the innermost covering membrane of the spinal cord, is thin and transparent,
and closely follows all the surface features of the spinal cord
The spinal pia also directly covers the roots of the spinal nerves and the
spinal blood vessels. Inferior to the conus medullaris, the spinal pia continues
as the filum terminale
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The spinal cord is suspended in the dural sac by the
filum terminale and the right and left denticulate
ligaments
Denticulate ligament (sawtooth) :
Triangular-shaped membranous extensions of the pia
mater
suspend the spinal cord in the middle of its dural sheath
The 20-22 sawtooth-like processes attach to the inner
surface of the arachnoid-lined dural sac.
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The arteries derive from :
1.Vertebral artery
2. Ascending cervical artery
3. Deep cervical artery
4. Intercostal artery5. Lumbar artery
6. Lateral sacral artery
7. Three longitudinal artery :
An anterior spinal artery
Two posterior spinal artery
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The arteries derive from :
8. Anterior segmental artery
9. Posterior segmental artery
10. The great anterior segmental
medullary artery (ofAdamkiewicz)
Contribute to the longitudinal
artery
The great anterior segmental
medullary artery (ofAdamkiewicz) is the largest
segmental medullary artery
supply cervical & lumbosacral
enlargment
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The arteries derive from :
11. Radicular artery
At levels where there are no
segmental medullary artery,radicular artery supplies the
posterior & anterior roots of
the spinal nerves
Radicular artery are shown
at only the cervical &thoracic level, but they also
occur at the lumbar & sacral
levels
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The arteries derive from :
12. Sulcal artery
Arise from the anterior spinal
artery & enter the spinal cordthrough anterior median
fissure
Supplies approximately two
thirds of the cross sectional
area of the spinal cord
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1. three anterior spinal veins
2. three posterior spinal veins
Drain up to :
1. 12 anterior medullary veins
2. 12 posterior medullary veins
3. radicular veins
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The gray matter on each side of the spinal cord is subdivided into regions called
horns.
The gray matter consist of :
The posterior (dorsal) gray horns
The anterior (ventral) gray horns
The lateral gray horns
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contain cell bodies and axons of interneurons as well as axonsof incoming sensory neurons.
The posterior(dorsal) gray
horns
contain somatic motor nuclei, which are clusters of cell bodiesof somatic motor neurons that provide nerve impulses forcontraction of skeletal muscles
The anterior(ventral) gray
horns
present only in thoracic and upper lumbar segments of thespinal cord.
contain autonomic motor nuclei, which are clusters of cellbodies of autonomic motor neurons that regulate the activityof cardiac muscle, smooth muscle, and glands.
The lateralgray horns
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The white matter on each side of the spinal cord is subdivided into regions called
columns/ funiculus
The white matter consist of :
The posterior (dorsal) white columns /funiculus
The anterior (ventral) white columns/funiculus The lateral white columns/funiculus
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Each column in turn contains distinct bundles of axons
having a common origin or destination and carrying similar
information.
These bundles, which may extend long distances up or
down the spinal cord, are called tracts.
Recall that tracts are bundles of axons in the CNS,whereas nerves are bundles of axons in the PNS
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In transverse sections of the spinal cord, the anterior and posterior gray
columns on each side are connected by a transverse gray commissure; the
gray matter resembles the letter H
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In the center of the gray commissure is situated the central canal.