CNS

1. The Spinal Cord
Dr M Idris Siddiqui
•Lower elongated part of CNS
enclosed in vertebral canal
•Present in upper 2/3rd
of vertebral column

2. • Resides inside
vertebral canal
• Extends to L1/ L2
• 31 segments, each
associated with a
pair of dorsal root
ganglia
• Two enlargements
Adult spinal cord:Adult spinal cord:

6. The spinal cord
• The spinal cord is an elongated, approximately
cylindrical part of the CNS, occupying the
superior two-thirds of the vertebral canal.
• Its average length in European males is 45 cm,
its weight 30 g.
• It extends from the upper border of the atlas to
the junction between the first and second
lumbar vertebrae. This lower level varies.
• The spinal cord is enclosed in the dura,
arachnoid and pia mater, separated from each
other by the subdural and subarachnoid spaces
respectively.
– The subdural space is a potential space.
– The subarachnoid space contains cerebrospinal
fluid (CSF). .

7. The spinal cord
• The cord is continuous cranially with
the medulla oblongata, and narrows
caudally to the conus medullaris, from
whose apex a connective tissue
filament, the filum terminale,
descends to the dorsum of the first
coccygeal vertebral segment.
• The spinal cord varies in transverse
width, gradually tapering
craniocaudally, except at the levels of
the enlargements.

8. Gross Features of the Spinal Cord
and Nerve Roots
• The spinal cord is a cylindrical structure.
• It is slightly flattened dorsoventrally and located in
the spinal canal of the vertebral column.
• Protection for the cord is provided by:
– The vertebrae and their ligaments;
– And the meninges and a cushion of CSF.
• The innermost layer of pia mater adheres to the
surface of the spinal cord.
• The outermost layer of dura mater forms a tube that
extends from the level of the foramen magnum to S2.
• It is continuous with the dura mater around the brain.

9. External features of spinal cord
•1.Fissures & sulci
•2.Attachments of spinal
nerves
•3.Enlargements
•4.Cauda equina
•5.Supports

10. Principal Parts
• 1. 42-45 cm in length; 2.5 cm wide
• 2. Cervical enlargement - C4-T1 supply upper
limbs
• 3. Lumbar enlargement - T9-T12 supply lower
limbs
• 4. Conus medullaris - tapers off to end at L1-L2
• 5. Filum terminale - pia mater anchors cord to
coccyx
• 6. Cauda equina - (horse tail) nerves below L2

11. Things to Note
• 1. Cord itself ends at L1-L2 vertebrae
• 2. Lower nerves dangle down in the cauda
equina
• 3. There are 31 pairs of spinal nerves
• 4. Each spinal segment - gives rise to one
spinal nerve pair.
• 5. C1-C7 spinal nerves project ABOVE C1-C7
vertebrae
• 6. C8 spinal nerve projects below C7 vertebra
• 7. T1-S5 spinal nerves project BELOW T1-S5
vertebrae

20. 1. posterior horn1. posterior horn
2. anterior horn2. anterior horn
3. intermediate zone3. intermediate zone
(intermediate gray)(intermediate gray)
4. lateral horn4. lateral horn
5. posterior funiculus5. posterior funiculus
6. anterior funiculus6. anterior funiculus
7. lateral funiculus7. lateral funiculus
8. Lissauer's tract8. Lissauer's tract
9. anterior median9. anterior median
fissurefissure
10. posterior median10. posterior median
sulcussulcus
11. anterolateral11. anterolateral
sulcussulcus
12. posterolateral12. posterolateral
sulcussulcus
13. Posterior13. Posterior
intermediateintermediate
sulcussulcus

22. 1.Fissures and sulci
• Fissures and sulci extend along most of the external surface.
– An anterior median fissure and
– A posterior median sulcus and
– Septum: Almost completely separate the cord into right and left halves,
but they are joined by a commissural band of nervous tissue which
contains a central canal.
• The anterior median fissure extends along the whole ventral
surface with an average depth of 3 mm, although it is deeper at
caudal levels. It contains a reticulum of pia mater. Dorsal to it is
the anterior white commissure.
– Perforating branches of the spinal vessels pass from the fissure to the
commissure to supply the central spinal region.
• The posterior median sulcus is shallower, and from it a
posterior median septum of neuroglia penetrates more than
halfway into the cord, almost to the central canal. The septum
varies in anteroposterior extent from 4 to 6 mm, and diminishes
caudally as the canal becomes more dorsally placed and the
cord contracts.

23. Spinal cord
cross-section

24. Fissures & sulci
• Each half is further subdivided into
posterior, lateral & anterior regions by
anterolateral & posterolateral
sulci.Through anterolateral sulcus
emerge anterior nerve roots &
through posterolateral sulcus enter
posterior root fibres of spinal nerves.
• *A dorsal intermediate sulcus exists in
cervical region, dividing each
posterior funiculus into two large
tracts: the fasciculus gracilis (medial)
and fasciculus cuneatus (lateral).

28. 2.Attachments of spinal nerves
• Spinal segment: spinal cord is divided into different segments. The portion
of spinal cord associated with a pair of single spinal nerve is called spinal
segment. There is no external indication of segments.
Relationship of spinal cord segments to vertebral
numbers:
• Because spinal cord is shorterer than vertebral
canal segments do not correspond to
vertebrae numerically that lie at same level.
• Each spinal is attached to spinal cord by
anterior motor root & posterior sensory root.
Each root is attached to cord by a series of
rootlets which extend to whole length of
corresponding segment of cord . Each sensory
nerve root possesses a posterior root ganglia,
the cells of which give rise to peripheral &
central nerve fibres.

29. R.J.Last
• Each anterior root is formed of 3-4 rootlets.
• Each posterior root is formed of several rootlets. A
short distance from cord the rootlets are combined
into single root.
• Theanterior & posterior roots pass from cord to
their corresponding intervertebral foramina.
• Anterior & posterior roots of spinal nerves pass
through spinal dura extends over nerve roots.
• The dural sheaths reach up to intervertebral
foramen & is attached to margins of intervertebral
foramina.
• The anterior & posterior nerve roots meet in
intervertebral foramin to form single mixed spinal
nerve.

30. Segmental Innervation: Dermatomes & MyotomesSegmental Innervation: Dermatomes & Myotomes
Moore’s COA5 2006
somaticsomatic
sensorysensory
nervenerve
(GSA)(GSA)
somaticsomatic
motormotor
nervenerve
(GSE)(GSE)
Dermatome: cutaneous (skin)
sensory territory of a single spinal
nerve
Myotome: mass of muscle
innervated by a single spinal nerve
spinal
nerve
skin
(dermatome)
muscle
(myotome)

31. Segmental Spinal Nerves and
Gross Features
• The segmental nature of the spinal cord is
demonstrated by the presence of 31 pairs of
spinal nerves.
• There is, however, little indication of
segmentation in its internal structure.
• Each dorsal root is broken up into a series
of rootlets that are attached to the cord
along the corresponding segment.
• The ventral root arises similarly.
• The spinal nerves are distributed as:
– Cervical8
– Thoracic12
– Lumbar5
– Sacral5
– Coccygeal1
• The first cervical nerves lack dorsal roots
in 50% of people, and the coccygeal nerves
may be absent.
Cervical 8
Thoracic 12
Lumbar 5
Sacral 5
Coccygeal 1

32. Relationships of Spinal Cord Segments to Vertebral Numbers
Because the spinal cord is shorter than the vertebral column, the spinal cord segments do not
correspond numerically with the vertebrae that lie at the same level. The following list helps
determine which spinal segment is contiguous with a given vertebral body.
Vertebrae Spinal Segment
Cervical Add 1
Upper thoracic Add 2
Lower thoracic (T7 to 9) Add 3
Tenth thoracic L1 and 2 cord segments
Eleventh thoracic L3 and 4 cord segments
Twelfth thoracic L5 cord segment
First lumbar Sacral and coccygeal cord
segments

33. Region Shape White Matter
Gray Matter
Anterior Gray Column Posterior Gray Column Lateral Gray Column
Cervical Oval Fasciculus cuneatus
and fasciculus gracilis
present
Medial group of cells
for neck muscles;
central group of cells
for accessory
nucleus (C1-5) and
phrenic nucleus (C3-
5); lateral group of
cells for upper limb
muscles
Substantia gelatinosa
present, continuous with
Sp.N. of cranial nerve V
at level C2; nucleus
proprius present;
nucleus dorsalis
(Clarke's column)
absent
Absent
Thoracic Round Fasciculus cuneatus
(T1-6) and fasciculus
gracilis present
Medial group of cells
for trunk muscles
Substantia gelatinosa,
nucleus proprius,
nucleus dorsalis
(Clarke's column), and
visceral afferent nucleus
present
Present; gives rise to
preganglionic
sympathetic fibers
Lumbar Round
To oval
Fasciculus cuneatus
absent; fasciculus gracilis
present
Medial group of cells
for lower limb
muscles; central
group of cells for
lumbosacral nerve
Substantia gelatinosa,
nucleus proprius,
nucleus dorsalis
(Clarke's column) at L1-
4, and visceral afferent
nucleus present
Present (L1-2 [3]);
gives rise to
preganglionic
sympathetic fibers
Sacral Round Small amount;
fasciculus cuneatus
absent; fasciculus gracilis
present
Medial group of cells
for lower limb and
perineal muscles
Substantia gelatinosa
and nucleus proprius
present
Absent; group of cells
present at S2-4, for
parasympathetic
outflow
Comparison of Structural Details in
Different Regions of the Spinal Corda

35. 3.Enlargements
There are two fusiform swellings opposite to
attachment of roots contributing to formation of
brachial & lumbosacral plexuses which are
cervical & lumber due to prescence of large no.
of motor neurons.
Cervical enlargement Lumbar enlargement
• Extent fromC4 to T2 from L2 to S3
spinal segments spinal segments
• Widest about 38mm about 35
mm at S1 Circumference at C6 segment
segment
• Innervation: muscles of upper muscles of lower
limb limb

36. Cervical EnlargementCervical Enlargement

37. 4.Cauda equina
• Because of disproportionate growth in length of
vertebral column during development compared with
that of spinal cord ,the length of nerve roots increases
progressively from above downwards to emerge
through correcponding intervertebral foramin.
• In upper cervical region spinal nerve roots are shorter
& run almost horizontally but roots of lumbar & sacral
nerves below level of termination of cord (at lower
border of L1 in adults) form a vertical leash around
filum terminale. Together these nerve roots are called
–cauda equina.
• Cauda equine consists of roots of lower 4 pairs of
lumbar, 5 pairs of sacral & 1 pair of coccygeal nerves.
• As a result of unequqal growth of vertebral column &
spinal cord progressive ascending of nerve roots
forming cauda equina

38. The Cauda Equina
Origin [L. horse tail]
The bundle of spinal nerve roots arising from
the lumbosacral enlargement and medullary
cone and running through the lumbar cistern
(subarachnoid space) within the vertebral canal
below the first lumbar vertebra; it comprises the
roots of all the spinal nerves below the first
lumbar.
• The lumbosacral roots are the longest, and
constitute the cauda equina (L. horsetail) in
the lower part of the subarachnoid space.

39. Inferior End of
Spinal Cord
• Conus medullaris - inferior
end of spinal cord proper
• Cauda equina - individual
spinal nerves within spinal canal
• Filum terminale -
filamentous end of meninges,
"tie-down"

40. 5.Supports
1. Filum terminale:
Pial extension from conus medullaris to back of coccyx, 20 cm
long, consists of mostly nonneural tissue(only in upper part
some rudiments of S1,S2,S3,S4 exist). Central canal of spinal
cord extends into upper part of of filum terminale for about 5mm.
There are two parts
i) Dural part(filum terminale externum), extends 5 cm length, lie
outside dural sac. i.e. below level of S2 vertebrae via sacral
hiatus also called “coccygeal ligament”
ii) Pial part (filum terminale internum)15 cm long lies within dural
sac.
2. Ligamentun denticulate:Longitudinally running two bands of
pia mater on each side along a line on lateral aspect of spinal
cord from framen magnum to conus medullaris between anterior
& posterior nerve roots. Its lateral edge has a series of teeth like
projections(average 21) which pierce arachnoid mater to be
attached to inner surface of dura between points of emergence of
spinal nerves.It helps to anchor spinal cord.
3. Dura mater: attaches to margins of intervertebral foramen &
above to margins of foramen magnum

41. The filum terminale
• The filum terminale, a filament of connective tissue
20 cm long, descends from the apex of the conus
medullaris. The cord tapers into a slender filament
called the filum terminale.It consists of pia mater
and neuroglial elements.
• A capacious part of the subarachnoid space
surrounds the filum terminale internum, and is the
site of election for access to the CSF (lumbar
puncture).
• This lies in the midst of the cauda equina and has a
distinctive bluish-white colour.
• It is a vestige of the spinal cord of the embryonic
tail, but in the adult it has no functional
significance.

42. The filum terminale
The filum terminale internum:
– Its upper 15 cm, is continued within extensions of the
dural and arachnoid meninges and reaches the caudal
border of the second sacral vertebra.This results in the
coccygeal ligament and it attaches to the dorsum of the
coccyx.
The filum terminale externum:
– Its final 5 cm, fuses with the investing dura mater, and
then descends to the dorsum of the first coccygeal
vertebral segment. The filum is continuous above with
the spinal pia mater. A few strands of nerve fibres which
probably represent roots of rudimentary second and third
coccygeal spinal nerves adhere to its upper part. The
central canal is continued into the filum for 5-6 mm.

43. The Denticulate Ligament
• A denticulate ligament on each side suspends the
spinal cord in the dural sheath.
• This ligament is in the form of a ribbon.
• It is attached along the lateral surface of the cord
midway between the dorsal and ventral roots.
• The lateral edge of the denticulate ligament is
serrated.
• 21 points or processes are attached to the dural
sheath at intervals between the foramen magnum
and the level at which the dura mater is pierced by the
roots of the first lumbar spinal nerve.

45. The denticulate ligament is a
serrated shelf-like extension of
the spinal pia mater projecting
between the posterior and the
anterior nerve roots in a frontal
plane from either side of the
cervical and thoracic regions of
the spinal cord. Its relatively
strong, tooth-like processes
anchor the spinal cord within
the subarachnoid space.

48. Terminal ventricle
Syn: ventriculus terminalis.
• A dilation of the central canal of the spinal
cord at the tip of the medullary cone.

49. Lumbar cistern
• Down distal to termination of
spinal cord subarachnoid space
around filum terminale
becomes roomy forming a pool
of CSF.

53. Epidural Space
• This is a space filled with fatty
tissue and contains a venous
plexus.
• It occupies the interval between
the dural sheath and the wall
of the spinal canal.

54. Contents of the Vertebral Canal
• The spinal cord,
• Spinal nerve roots, and
• Spinal meninges and
• The neurovascular structures
that supply them are located
within the vertebral canal

55. 3) Pia mater
2) Arachnoid
1) Dura mater
Spinal MeningesSpinal Meninges
Three membranes
surround all of CNS
1) Dura materDura mater - "tough
mother", strong
2) Arachnoid meninxArachnoid meninx -
spidery looking, carries
blood vessels, etc.
Subarachnoid space
3) Pia materPia mater - "delicate
mother", adheres tightly
to surface of spinal cord

56. Dorsal and Ventral Roots and
Gross Features
• The dorsal and ventral roots traverse the
subarachnoid space and pierce the arachnoid and
dura mater.
• At this point, the dura becomes continuous with the
epineurium.
• After a short course in the epidural space the roots
reach the intervertebral foramina.
• The dorsal root ganglia are located here.
• The dorsal and ventral roots join immediately distal
to the ganglion to form the spinal nerve.
• The length and obliquity of the roots increase
progressively in a posteroinferior direction.

57. INTERNAL STRUCTURE OF
SPINAL CORD
• It is composed of
–Central mass of grey matter
–Central canal surrounded by
grey matter
–Peripheral cylindrical masses of
white matter

59. Organization of Cord CrossOrganization of Cord Cross
SectionSection
Gray matter - interior horns
posterior - somatic and visceral sensory nuclei
anterior (and lateral) gray horns – somatic and visceral motor control
gray commissures - axons carrying information from side to side
White matter - tracts or columns
posterior white column -
anterior white column
lateral white column
anterior white commissure
functions
ascending tracts - sensory toward brain
descending tracts - motor from brain

60. Spinal Cord Structure - Cross Section
• A. Grey vs. White Matter
• 1. Grey matter - nerve cell bodies motor &
interneurons
• 2. White matter - myelinated axons of motor
& sensory
• B. Regions in the Grey Matter - H shaped center
• 1. Grey commissure - cross bar of the H
• 2. Central canal - hole in the center
• 3. Anterior (ventral) horns
• 4. Posterior (dorsal) horns
• 5. Lateral (intermediate) horns (T, L, S only)

61. CENTRAL CANAL
• The cavity of the spinal cord is called the canalis
centralis.
• It is the continuation of the ventricles of the
brain.
• It is layered by a special type of glial cells called
ependyma (morphologically, it appears to be
simple columnar epithelium with a process on
each cell).
• The canal has a small amount of cerebrospinal
fluid continuous with that of the ventricles of the
brain.

62. – Shape: butterfly shaped or seen as H shaped pillars
with anterior & posterior columns or horns united by
a thin crossbar grey commissure containing central
canal which expands in conus medullaris to form
terminal ventricle. Centra canal is lined by
ependyma.
• A small lateral grey column or horn is present in thoracic
or upper lumbar segments of cord.
• Grey matter surrounding central canal is called substantia
gelatinosa centralis, consists of anterior & posterior grey
commissure.
– Composition:neuronal cell bodies, dendrites with
their synapses, glia, blood vessels.
Grey matter

63. White matter
–Shape:The grey matter H & external
longitudinal sulci demarcate 3
columns or funniculi;dorsal,ventral &
lateral which extend in length of
spinal cord.
–Composition: bundles of nerve
fibres. Blood vessels

64. General Pattern of Grey and White Matter
• The general pattern of grey matter and white matter is
the same throughout the spinal cord.
• There are, however, some regional differences that
are apparent in transverse sections.
• The amount of white matter increases in a caudal-
to-cranial direction because fibres are added to
ascending tracts and fibres leave descending
tracts to terminate in the grey matter.
• There is increased volume of grey matter in the
cervical and lumbosacral enlargements for
innervation of the limbs.
• The small lateral horn of grey matter is
characteristic of the thoracic and upper lumbar
segments.

65. • The relative amount of grey & white matter &
size & shape of grey columns vary at different
levels of spinal cord. The amount of white
matter with mass of tissue to be supplied
greatest at cervical & lumbar enlargements
which supply limbs.
• The amount of white matter increases as
proceed up the spinal cord because
progressively more & more ascendindg fibres
are added as go up. Number of descending
fibres decrease as go down as some of them
terminate in each segment

67. Regions in the White Matter - fibre tracts
• 1. Anterior (ventral) column
• 2. posterior (dorsal) column
• 3. Lateral (intermediate) column
. Fasciculi/tracts - axon bundles with common
function
– a. Ascending tracts - sensory to the brain
– b. Descending tracts – brain motor neurons

68. Structure of grey matter
• Neurons are arranged in nuclei or laminae in grey
matter of spinal cord.
• Structually---
– a-Golgi type I(which leave grey matter),
– b-Golgi type II (which do not leave grey matter
--inter or intrasegmental),
• Functionally---
– a- Motor neurons present in anterior & lateral
horns;
• Alpha neurons(LMN),
• Gamma neurons
– b- Sensory neurons in posterior grey column
– c- Interneurons also called associated neurons

70. White Matter• This consists of 3 funiculi (these are often called "columns" but this word is
more appropriate for longitudinally aligned arrays of neuronal cell
bodies in the grey matter).
– The dorsal funiculus is bounded by the dorsal septum and
the dorsal grey horn. It consists of a medial fasciculus
gracilis and a lateral fasciculus cuneatus above the
midthoracic level.
The fasciculus gracilis corresponds with the entire dorsal
funiculus caudal to the midthoracic region.
• There is no anatomical demarcation between the lateral and ventral funiculi.
– The lateral funiculi are further subdivided into dorsolateral
and ventrolateral funiculi. These are separated by a plane
that passes through the central canal and the denticulate
ligament.
• The dorsolateral tract (of Lissauer) occupies the interval between
the apex of the dorsal horn and the surface of the cord.
– The ventral/anterior funiculus, between anterior median fissure
& anterior grey horn
• The white matter consists of partially overlapping fibre bundles.

73. Spinal Grey MatterPosterior Horn
• The posterior horn consists mainly of interneurons.
• The processes of these remain within the spinal cord and of tract cells whose
axons collect into long ascending sensory pathways.
• This area of grey matter contains 3 prominent parts:
1. The substantia gelatinosa of Rolando;
• This is a distinctive region that caps the posterior horn at all spinal levels.In
myelin-stained preparations this region looks pale compared with the rest of
the grey matter.
• It deals mostly with finely myelinated and unmyelinated sensory fibres that
carry pain and temperature information.
Lissauer's Tract (posterolateral tract of Lissaure)
• This is relatively pale staining area between the substantia gelatinosa and the
surface of the cord.
2. The body of the posterior horn.(Nucleus Proprius)
• This consists mainly of interneurons and tract cells.
• These transmit many types of somatic and visceral sensory information.
• In this respect it functionally overlaps parts of the intermediate grey matter.
3. The nucleus dorsalis(Clark’s column)
4. The visceral afferent nucleus

74. • Substantia gelatinosa of Rolando(SGR):
• Situated at apex. It receives afferent fibres concerned with pain,
temperature & touch from posterior root. It is continuous above
with nucleus of spinal tract of V nerve.
• Nuceus proprius:
• Lies anterior to Substantia gelatinosa of Rolando(SGR) & form
main bulk of cells in posterior grey column. Receives fibres
from posterior white column associated with propioception
i.e.two point discrimination & vibration
• Nucleus dorsalis (clark’s column)
• Situated at medial part of of base of posterior grey column,
extends from C8 to L2,L3.
• Receives propioceptive afferent fibres of touch, pressure from
trunk & lower limbs.
• Visceral afferent nucleus:
• Located lateral to nucleus dorsalis from T1 to L2 & S2 to S4.
Recieves visceral afferent from dorsal nerve roots.

76. Nucleus Dorsalis (Clarke's nucleus)
• This is a rounded collection of large cells located on
the medial surface of the base of the posterior horn
from about C8 or T1 to L2 or L3.
• It is particularly prominent at lower thoracic levels.
• This is an important relay nucleus for the
transmission of information to the cerebellum.
• It also plays a role in forwarding proprioceptive
information from the leg to the thalamus.
• It is considered by many to be part of the posterior
horn, due to its role in sensory processing.

77. Lateral grey column/Intermediate Grey
Mater
• This is intermediate to the anterior and
posterior horns. This forms the pointy lateral
horn of the spinal grey matter
• Two nuclei.
1.Intermediolateral,from T1 to L2 give rise to
preganglionic fibres of sympathetic nervous
system which leave along anterior nerve roots.
2. Intermediomedial: from S2 to S4 give origin
to preganglionic fibres of parasympathetic
nervous system pass through anterior nerve
roots.

80. Rexed Laminae
• Laminar Architecture of grey mater:
(Rexed Laminae)10 zones of laminae of
Rexed shown by Roman numerals,
starting at tip of posterior horn moving
ventrally into anterior horns.e.g.

81. Lamina of RexedLamina of Rexed

82. Rexed's Laminae
•In 1952 Rexed devised a system for subdividing the grey matter of the cat's spinal
cord. The same system has since been applied to the cords of other mammals,
including humans.
Lamina I Lamina marginalis
Lamina II Corresponds to the substantia gelatinosa
lamina III Some workers consider that the substantia gelatinosa contains part or all of
lamina III as well as lamina II.
Lamina IV The ill-defined nucleus proprius of the dorsal horn corresponds to some of
the cell constituents of laminae III and IV.
Lamina V A thick layer which includes the neck of the dorsal horn. It is divisible into
a lateral third and medial two-thirds.
Lamina VI Corresponds approximately to the base of the dorsal horn.
Lamina VII Includes much of the intermediate (lateral) horn. It contains prominent
neurones of Clarke's column (nucleus dorsalis, nucleus thoracis, thoracic
nucleus) and intermediomedial and intermediolateral cell groupings.
Lamina VIII A mass of propriospinal interneurones.
Lamina IX A complex array of cells consisting of α and γ motor neurones and many
interneurones.
Lamina X Surrounds the central canal and consists of the dorsal and ventral grey
commissures.

87. Nuclear grouping in grey column
• Anterior grey column:
– Medial: ventromedial, dorsomedial extend almost all length of cord
innervate muscles of neck & trunk
– Lateral: only in cervical, lumbosacral enlargements supply limb muscles
– Central:
• a Phrenic nucleus; in cervical region C3-C5 for diaphragm
• b. Lumbosacral nuceus;from L2-S3 function unknown
• c. Spinal accessory nuceus;C1-C5 give rise to spinalroots of XI cranial
nerve
• Posterior grey column:
• 4 longitudinal groups from apex to (posterior) to base(anterior)
– Two extend through the length of cord:
• Substantia gelatinosa of Rolando(SGR)
• Nucleosus propius
• Two confine to thoracic & lumbar regions:
– Nucleus dorsalis(Clark’s column)
– Visceral afferent nucleus

91. ArteriesA. Anterior Spinal Artery
This artery is formed by the midline union of paired branches of the vertebral
arteries. It descends along
the ventral surface of the cervical spinal cord, narrowing somewhat near T4.
B. Anterior Medial Spinal Artery
This artery is the prolongation of the anterior spinal artery below T4.
C. Posterolateral Spinal Arteries
These arteries arise from the vertebral arteries and course downward to the lower
cervical and upper thoracic segments.
D. Radicular Arteries
Some (but not all) of the intercostal arteries from the aorta supply segmental
(radicular) branches to the spinal cord from Tl to LI. The largest of these branches,
the great ventral radicular artery, also known as the arteria radicularis magna, or
artery of Adamkiewicz, enters the spinal cord between segments T8 and L4. This
artery usually arises on the left and, in most individuals, supplies most of the arterial
blood supply for the lower half of the spinal cord. Although occlusion in this artery is
rare, it results in major neurologic deficits (eg, paraplegia, loss of sensation in the
legs, urinary incontinence).

92. Arteries
E. Posterior Spinal Arteries
These paired arteries are much smaller than the single large anterior
spinal artery; they branch at various levels to form the posterolateral
arterial plexus. The posterior spinal arteries supply the dorsal white
columns and the posterior portion of the dorsal gray columns.
F. Sulcal Arteries
In each segment, the branches of the radicular arteries that enter the
intervertebral foramens accompany the dorsal and ventral nerve
roots. These branches unite directly with the posterior and anterior
spinal arteries to form an irregular ring of arteries (an arterial corona)
with vertical connections. Sukal arteries branch from the coronal
arteries at most levels.
Anterior sulcal arteries arise at various levels along the cervical and
thoracic cord within the ventral sulcus they supply the ventral and
lateral columns on either side of the spinal cord.

93. Veins
• An irregular external venous plexus lies in the
epidural space; it communicates with
segmental veins, basivertebral veins from the
vertebral column, the basilar plexus in the
head, and, by way of the pedicular veins, a
smaller internal venous plexus that lies in the
subarachnoid space. All venous drainage is
ultimately into the venae cavae. Both plexuses
extend the length of the cord.
• Basivertebral vein
• one of a number of veins in the spongy substance of the bodies of the vertebrae, emptying into the anterior internal vertebral venous plexus.

98. Arterial supply : Supplied by 3 small arteries + feeder arteries
•ASA & PSA arteries are reinforced by segmental arteries, which enter the vertebral
canal through the inter vertebral foramina
•These arteries are branches of arteries outside the vertebral column
(Deep cervical, Intercostal & Lumbar arteries)
•Segmental arteries give rise to anterior & posterior radicular arteries
Feeder arteries
•Enter the vertebral arteries & anastomose with the ASA & PSA
•The most important feeder artery is the Great anterior medullar artery of Adamkiewicz
∀It arises from the aorta at lower thoracic or upper lumbar vertebral levels
∀Unilateral
∀In the left side of most people
Major source of blood to the lower 2/3 of the spinal cord

99. Segmental spinal arteries

104. Venous drainage of vertebral
column.
• A. The venous drainage parallels the arterial supply
and enters the external and internal vertebral venous
plexuses. There is also anterolateral drainage from the
external aspects of the vertebrae into segmental
veins.
• B. The vertebral canal contains a dense plexus of thin-
walled valveless veins, the internal vertebral venous
plexuses, which surround the dura mater. Anterior and
posterior longitudinal venous sinuses can be identified
in the internal vertebral venous plexus. Basivertebral
veins from the vertebral body drain primarily into the
anterior internal vertebral venous plexus, but they may
also drain to the anterior external plexus.

105. Venous Drainage of the Spinal Cord
• This is by 6 irregular, plexiform channels.
• Drains mainly into the veins of the brain & the venous
sinuses via 6 tortuous longitudinal channels
• Finally drain into the internal vertebral venous plexus
• There is one along:
– The anterior and posterior midlines;
– Along the line of attachment of the dorsal roots of each side;
– Along the line of attachment of the ventral roots of each side.
• These are drained by the radicular veins.
• Each, in turn empty into the epidural venous plexus.

107. Anatomy of a Reflex
A. Structures Involved
• 1. Dorsal (posterior,sensory) root
All afferent (sensory) fibers from periphery
• 2. Dorsal (sensory) root ganglion
Contains sensory nerve cell bodies (bipolar)
• 3. Ventral (anterior,motor) root
Motor nerve AXONS only
– i. Skeletal motor neurons (anterior horn)
– ii. Smooth/cardiac/gland neurons (lateral horn)

108. The Simple Reflex Arc
• 1. A special type of conduction pathway
• 2. Receptor - responds to internal/external stimulus
• 3. Sensory Neuron - passes impulse to CNS
• a. impulse sent along nerve from that organ
• b. eventually reaches DORSAL ramus of spinal nerve
• c. synapses on neuron somewhere in grey matter
• 4. Center - point in the CNS where message is accepted
• a. sometimes directly to the effector motor neuron
• b. most times on an INTERNEURON of dorsal horn
• c. passes message to motor neuron in VENTRAL
• HORN
• d. or passes message to brain via specific tract
• 5. Motor neuron - sends signal to appropriate effector
• a. resides in anterior horn - skeletal muscle
• b. resides in lateral horn - smooth/cardiac/gland
• 6. Effector Organ - organ effected by motor neuron
• a. simple reflexes and motion - skeletal muscle
• b. general physiological - other organs

109. Major Clinical Reflexes
• 1. patellar reflex (knee jerk)
• 2. Achilles reflex (ankle jerk)
• 3. Babinski sign -
»positive (under 1 1/2 years old)
»negative (after 1 1/2 years old)
• 4. abdominal reflex

110. Different Reflexes
• 1. Spinal reflexes - spinal cord controlled (posture)
• 2. Somatic reflexes - skeletal muscles
• 3. Cranial reflexes - brain and cranial nerves
• 4. Visceral (autonomic) r. - smooth/cardiac/glands
• 5. stretch reflex - monosynaptic
• a. muscle spindle organ (sense stretch)
• b. sensory neuron -> motor neuron
• c. ipsilateral (same side) reflex arc
• d. patellar tendon reflex
• e. reciprocal innervation - excitatory/inhibitory
• 6. tendon reflex - polysynaptic
• a. Golgi tendon organs (sense tension)
• b. sensory neuron -> interneuron -> motor neuron
• c. ipsilateral reflex arc
• d. also reciprocal innervation
• 7. flexor (withdrawal) reflex polysynaptic
• a. pain receptors
• b. sensory -> interneurons -> many motor neurons
• c. intersegmental reflex arc
• i. many spinal segments involved in response
• ii. complex movement is coordinated
• d. crossed-extensor reflex
• i. sensory message crosses to opposite side
• ii. allows contralateral muscle response
• iii. maintain body balance during reflex

111. Major Clinical Reflexes
• 1. patellar reflex (knee jerk)
• 2. Achilles reflex (ankle jerk)
• 3. Babinski sign -
»positive (under 1 1/2 years old)
»negative (after 1 1/2 years old)
• 4. abdominal reflex

113. Spinal Lumbar Puncture
• To obtain a sample of CSF from the
subarachnoid space, a spinal lumbar
puncture is the preferred method.
• The needle is inserted between the arches of
L3 and L4.
• This avoids any damage to the spinal cord.

118. Anatomy of Complications of Lumbar Puncture
• Postlumbar puncture headache. This headache starts after
the procedure and lasts 24 to 48 hours. The cause is a leak of
cerebrospinal fluid through the dural puncture, and it usually
follows the use of a wide-bore needle. The leak reduces the
volume of cerebrospinal fluid, which, in turn, causes a
downward displacement of the brain and stretches the nerve-
sensitive meninges a headache follows. The headache is
relieved by assuming the recumbent position.
• Brain herniation. Lumbar puncture is contraindicated in cases
in which intracranial pressure is significantly raised. A large
tumor, for example, above the tentorium cerebelli with a high
intracranial pressure may result in a caudal displacement of the
uncus through the tentorial notch or a dangerous displacement
of the medulla through the foramen magnum, when the lumbar
cerebrospinal fluid pressure is reduced.

119. Block of the Subarachnoid Space
• A block of the subarachnoid space in the
vertebral canal, which may be caused by a
tumor of the spinal cord or the meninges, can
be detected by compressing the internal jugular
veins in the neck.
• This raises the cerebral venous pressure and
inhibits the absorption of cerebrospinal fluid in
the arachnoid granulations, thus producing a
rise in the manometric reading of the
cerebrospinal fluid pressure. If this rise fails to
occur, the subarachnoid space is blocked and
the patient is said to exhibit a positive
Queckenstedt's sign.

120. Caudal Anesthesia
• Solutions of anesthetics may be injected into the
sacral canal through the sacral hiatus. The solutions
pass upward in the loose connective tissue and
bathe the spinal nerves as they emerge from the
dural sheath. Caudal anesthesia is used in
operations in the sacral region, including anorectal
surgery and culdoscopy. Obstetricians use this
method of nerve block to relieve the pain during the
first and second stages of labor. Its advantage is
that, administered by this method, the anesthetic
does not affect the infant.
• The sacral hiatus is palpated as a distinct
depression in the midline about 1.6 in. (4 cm) above
the tip of the coccyx in the upper part of the cleft
between the buttocks. The hiatus is triangular or U
shaped and is bounded laterally by the sacral
cornua.

124. Spinal Cord Ischemia
• The blood supply to the spinal cord is
surprisingly meager, considering the
importance of this nervous tissue. The
longitudinally running anterior and posterior
spinal arteries are of small and variable
diameter, and the reinforcing segmental
arteries vary in number and in size. Ischemia
of the spinal cord can easily follow minor
damage to the arterial supply as a result of
regional anesthesia, pain block procedures, or
aortic surgery.

125. Brown-Séquard's syndrome
• syndrome with unilateral spinal
cord lesions, proprioception
loss and weakness occur
ipsilateral to the lesion, while
pain and temperature loss
occur contralateral.
• Syn: Brown-Séquard's paralysis.

126. Spinal Cord SyndromeSpinal Cord SyndromeSpinal Cord SyndromeSpinal Cord Syndrome
Brown-Sequard syndromeBrown-Sequard syndrome
(spinal cord hemisection)(spinal cord hemisection)
Major SymptomsMajor Symptoms
1. ipsilateral1. ipsilateral UMN syndromeUMN syndrome belowbelow the level of lesionthe level of lesion
2. ipsilateral2. ipsilateral LMN syndromeLMN syndrome atat the level of lesionthe level of lesion
3. ipsilateral loss of3. ipsilateral loss of discriminative touch sensationdiscriminative touch sensation andand
conscious proprioceptionconscious proprioception belowbelow the level of lesionthe level of lesion
(posterior white column lesion)(posterior white column lesion)
4.4. contralateralcontralateral loss ofloss of pain and temperaturepain and temperature sensationsensation
belowbelow the level of lesionthe level of lesion (spinothalamic tract lesion)(spinothalamic tract lesion)

129. Brown sequard syndrome (Hemi section of the spinal cord)
•Features
1.Ipsilateral LMN paralysis & muscular atrophy in the corresponding part of the body to the damaged segment
of the spinal cord
2.Ipsilateral spastic paralysis below the of the level lesion (γ motor neuron inhibition is lost)
3.Ipsilateral loss of cutaneous sensation below the of the level lesion
4.Ipsilateral loss of dorsal column sensation below the of the level lesion
5.Contralateral pain, temperature, touch & pressure sensations are lost below the of the level lesion
•Tracts which are affected
∀Dorsal column : Ipsilateral
∀Lateral Spinothalamic tract : Contralateral
∀Anterior Spinothalamic tract : Contralateral
∀Anterior Spino cerebellar tract : Contralateral
∀Posterior Spino cerebellar tract : Ipsilateral
∀Anterior corticospinal tract : Ipsilateral
∀Posterior corticospinal tract : Ipsilateral
∀Autonomic nervous system : Ipsilateral

132. Syringomyelia
• The presence in the spinal cord of longitudinal
cavities lined by dense, gliogenous tissue,
which are not caused by vascular insufficiency.
– Syringomyelia is marked clinically by pain and
paresthesia, followed by muscular atrophy of the
hands and analgesia with thermoanesthesia of the
hands and arms, but with the tactile sense
preserved; later marked by painless whitlows,
spastic paralysis in the lower extremities, and
scoliosis of the lumbar spine. Some cases are
associated with low grade astrocytomas or vascular
malformations of the spinal cord.
– Syn: hydrosyringomyelia, Morvan's disease, myelosyringosis, syringomyelus.

134. Spinal Cord Injuries
• The degree of spinal cord injury at different
vertebral levels is largely governed by anatomic
factors. In the cervical region, dislocation or
fracture dislocation is common, but the large
size of the vertebral canal often results in the
spinal cord escaping severe injury. However,
when considerable displacement occurs, the
cord is sectioned and death occurs
immediately.
• Respiration ceases if the lesion occurs above
the segmental origin of the phrenic nerves (C3,
4, and 5).