SPINAL CORD -1
SPINAL CORD
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The spinal cord is a long,
thin, tubular bundle of
nervous tissue and
support cells that extends
from the brain (the medulla
specifically).
It is the most important
content of the vertebral
canal. The upper end
continues with the medulla
oblongata at the level of
the upper border of the
first cervical vertebra. .
It is around 45 cm (18 in)
in men and around 43 cm
(17 in) long in women
Weight amounts to about
30 gms.
Conus medullaris
 The lower end lies at the level of lower border of the
first lumbar vertebra. This level can be variable
 The lower conical end is called CONUS
MEDULLARIS. The conus is continuous below with
a fibrous cord called FILUM TERMINALE.
Cervical and lumbosacral
enlargement
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The spinal cord possesses two
symmetrical enlargements which
occupy the segments of the limb
plexuses:
 cervical enlargement (C3 to T1) for
the brachial plexus and the
 lumbosacral enlargement (L2 to S3)
for the lumbar and sacral plexuses.
Both enlargements are due to the
greatly increased mass of motor cells in
the anterior horns of grey matter.
Fissures and sulci
 Anterior Median Fissure
A deep midline groove, present
on the ventral side
 It contains a double fold of pia
mater
 Posterior Median Sulcus
 Dorsally it shows a shallow
posterior median sulcus, from
which a posterior median
septum of neuroglia extends into
its substance.
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Spinal meninges
 Spinal cord is ensheathed by three
protective membranes, separated from
each other by two concentric spaces .
Dura mater outer most strong, fibrous
membrane
ends at the level of S2
Arachnoid thin, transparent sheath
Pia mater closely invests the spinal cord and sends delicate septa
into its substance.
Meningeal Spaces
 Epidural space between vertebral canal
and dura mater
 Subdural space
Between the dura mater and the arachnoid
contains lymph
 Subarachnoid space
Between arachnoid and pia mater
Filled with cerebrospinal fluid
Spinal Nerve Roots
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The anterior and posterior roots of the
spinal nerves unite within the intervertebral
foramina.
Within the subarachnoid space
the nerve roots are attached to
the spinal cord by a series of
rootlets.
Each anterior root is formed by
three or four rootlets which
emerge irregularly along the
anteriolateral surface of the
spinal cord.
Each posterior root is formed by
several rootlets, attached
vertically to the posterolateral
surface of the cord.
Posterior root has a spinal ganglion
Spinal Nerve Roots
 The pairs of spinal nerves are grouped as follows:
 cervical 8
 thoracic 12,
 lumbar 5,
 sacral 5,
 coccygeal 1
 Upper cervical roots are horizontal
 Upper thoracic roots slope down at an angle to
reach their foramen.
 Below L1 vertebra the roots pass almost vertically
downwards through the subarachnoid space,
forming the CAUDA EQUINA.
 The filum terminale extends down from the tip of
conus medullaris among the nerve roots of the
cauda.
INTERNAL STRUCTURE
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The spinal cord consists of a central
mass of grey matter (cell bodies), in the
form of a vertically grooved column
surrounding the central canal, enclosed
in a cylindrical mass of white matter
(fibers).
It is divided into two halves by the
anterior median fissure and the
posterior median septum. The septum
extends forwards as far as the grey
commissure (the central limb of the H in
cross-section) which connects the grey matter of the right and left
halves of the cord, and contains the central canal.
Grey matter
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Grey matter contains neural cell bodies, in contrast to white matter,
which does not and mostly contains myelinated axon tracts
In a transverse section each half of the gray substance is shaped
like a comma or crescent, the concavity of which is directed
laterally; and these, together with the intervening gray commissure,
present the appearance of the letter H.
An imaginary coronal plane through the central canal serves to
divide each crescent into an anterior or ventral, and a posterior
or dorsal column.
Anterior horn
 Anterior horn of the spinal cord (or anterior cornu, or anterior
column, or ventral horn) is the
ventral (front) grey matter section of
the spinal cord
 The more medial anterior horn cells
are concerned with the innervations
of trunk musculature, with more
lateral cells supplying the limbs
Posterior horn
 Posterior horn (posterior cornu,
dorsal horn, spinal dorsal horn) of
the spinal cord is the dorsal (more towards the back) grey matter of
the spinal cord.
 It receives several types of sensory information from the body,
including , proprioception, and vibration
Lateral horn
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Between the limb enlargements, from segments
T1 to L2, there is a small lateral horn, containing
preganglionic sympathetic cell bodies.
Their axons pass out in the anterior nerve roots
and enter the spinal nerves from T1 to L2.
A similar group of cells forms the small lateral
horn in sacral segments 2-4.
The cells of the grey matter in each half of the
cord lie in specific functional groups or laminae
designated by the Roman numerals I to X.
Laminae of grey matter
 The cells of the grey matter in each half of the cord lie in
specific functional groups or laminae designated by the
Roman numerals I to X.
 Among the more important cell
groups in the various laminae
are those of
 Lamina II which constitute the
gelatinous substance;
 Lamina V are a main source of
anterolateral tract
(spinothalamic and
spinoreticular) fibers;
 Lamina VII contains in its medial
part the thoracic nucleus and
laterally the
thoracolumbar(sympathetic) and
sacral (parasympathetic) lateral horn cells
 Other cells of lamina VII, together with those of lamina VIII, are
interneurons involved in coordinating motor activity and projecting
to lamina IX
 Lamina IX contains the α and γ motor
neurons which innervate skeletal muscle.
Central canal
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Central Canal (canalis centralis) runs throughout the entire length
of the medulla spinalis.
The portion of gray substance in front of the canal is named the
anterior gray commissure
that behind it, the posterior gray commissure
The central canal is continued upward through the lower part of the
medulla oblongata, and opens into the fourth ventricle of the brain;
below, it reaches for a short distance into the filum terminale
White matter
 The white substance of the spinal cord consists of medullated
nerve fibers imbedded in a spongelike net-work of neuroglia, and is
arranged in three funiculi :
 anterior, lateral, and posterior
 In each half of the cord the posterior
white column lies between the
posterior median septum and the
posterior grey horn. It is wholly
occupied by the ascending fibres of
the gracile and cuneate tracts, the
pathways for touch and some
associated sensations.
 The rest of the white matter forms
the lateral and anterior white
columns, the emerging anterior nerve roots. Both these columns
contain long ascending and descending tracts. Except in the
posterior columns, there is much intermingling of fibres and there
are no sharp boundaries to tracts.
Blood Supply
o The spinal cord is supplied by the (single) anterior
and (right and left) posterior spinal arteries which
descend from the level of the foramen magnum
and form three longitudinal channels from which
branches enter the cord. They are supplemented
at variable levels by anastomoses with a variable
number of radicular arteries.
Spinal veins
The spinal veins form loose-knit plexuses in which there are an
anterior and a posterior midline longitudinal vein, and on each side a
pair of longitudinal veins posterior to the anterior and posterior nerve
roots. These veins drain to the internal vertebral venous plexus, and
thence via the external vertebral venous plexus to the segmental
veins: vertebral in the neck; azygos in the thorax; lumbar in the lumbar
region; and lateral sacral in the sacral region. At the foramen magnum they
communicate with the veins of the medulla.