from residents slide

1. .
Anatomy and physiology of
spinal cord, ventricle and CSF
kendeneh B.(R1)
october 16, 2013

2. .
Out line
Anatomy of spinal cord
Physiology of spinal cord
Anatomy of ventricles
Physiology of CSF

3. objectives
 To know basic anatomy of sp. Cord
 To understand the position of the main nerve
pathways and nerve cell groups in the spinal cord
 To review basic structure of ventricle and to learn
how CSF produced

4. Spinal cord
 It stretches from upper border of the foramen
Magnum to the intervertebral disc between the
first and second lumbar vertebrae.
 In the newborns, it extends to the level of the
third lumbar vertebra
Due to the differential growth of the vertebral
column relative to the spinal cord, the spinal cord
segments do not always correspond to the
vertebral levels.

5. Accordingly, the cervical spinal nerves exit above
their corresponding vertebrae
 the remaining spinal nerves emerge from the
vertebral column below the corresponding
vertebrae.
When the dorsal and ventral roots of the lower
lumbar and sacral segments assume a longer
course around the conus medullaris to reach the
corresponding intervertebral foramina, the cauda
equina is formed

6. Spinal cord meniges
 is invested by the dura, arachnoid, and the pia
mater.
 The dura mater is comprised of an inner
meningeal and an outer endosteal layer.
The outer endosteal layer forms the periosteum of
the vertebral canal and the epineurium of the
spinal nerves at or slightly beyond the
intervertebral foramina.

7. .
 At the level of the second sacral vertebra the
spinal dura joins the filum terminale to attach to
the coccyx as the coccygeal ligament.
The epidural space contains the internal vertebral
plexus

8. .
The arachnoid mater is a loose, irregular, and
trabecular layer that is continuous with cranial
arachnoid mater.
 surrounds the spinal cord without following the
sulci.
 is pierced by vessels that supply the pia mater.

9. .
The pia mater
 It intimately adheres to the spinal cord, giving rise
to the dentate ligaments
 These ligaments are triangular extensions that
extend to the dura, coursing between the dorsal
and ventral roots.
 act as suspensory ligaments for the spinal cord

10. .

11. Blood supply of spinal cord

12. Arteries of the Spinal Cord and Nerve Roots
are branches of the vertebral, ascending cervical,
deep cervical, intercostal, lumbar, and lateral
sacral arteries
 Three longitudinal arteries supply the spinal cord:
- an anterior spinal artery
- paired posterior spinal arteries.
The anterior spinal artery, formed by the union of
branches of the vertebral arteries

13. Arteries of the Spinal Cord and Nerve Roots cont…d
 Sulcal arteries arise from the anterior spinal artery
and enter the spinal cord through this fissure.
 Each posterior spinal artery is a branch of either
the vertebral artery or the posteroinferior
cerebellar artery.
The posterior spinal arteries commonly form
anastomosing channels in the pia mater.

14. .

15. Arteries of the Spinal Cord and Nerve Roots cont…d
The anterior and posterior segmental medullary arteries .
The segmental medullary arteries are located chiefly where
the need for a good blood supply to the spinal cord is
greatest.
 They enter the vertebral canal through the IV foramina

16. Blood supply of vertebrae and spinal cord

17. ,
Veins of the Spinal Cord
 have a distribution similar to that of the spinal arteries.
 There are usually three anterior and three posterior spinal
veins .
 The veins draining the spinal cord join the internal
vertebral (epidural) venous plexus in the epidural space .
 The internal vertebral venous plexus communicate with
dural sinuses and vertebral veins in the cranium.
 The internal vertebral plexus also communicates with the
external vertebral venous plexus on the external surface of
the vertebrae.

18. .

19. Internal organization
 Each spinal segment consists of central gray and
peripheral white matters that are connected by the
corresponding gray and white commissures.
 The central canal is a tube that pierces the gray
commissure of the spinal cord

20. A. Gray matter
 consist of nerve cells & unmyelinated nerve fibers
 H-shaped formed of:
 anterior horns: containing motor nuclei.
 poster horns: containing sensory nuclei
 lateral horns containing autonomic cells

21. .

22. I. Nuclei of the posterior horn
1. Substatia gelatinosa
 situated at the apex of the posterior gray column
throughout the length of the spinal cord
receives afferent fibers concerned with pain,
temperature, & touch impulses via central processes of
dorsal root ganglion cells
its axons cross to the opposite side in the white
commissure & ascend in lat. white matter as the lat.
spinothalamic tract

23. Nuclei of the posterior horn cont…d
2. Nucleus Proprius
 Situated in the middle part of the post horn anterior to the
substantia gelatinosa throughout the spinal cord
 receives fibers from the posterior white column that are
associated with the senses of position & movement, two-point
discrimination, & vibration.
 its axons cross to the opposite side in the white commissure
then ascend in the ant white matter as ant. spinothalamic
tract

24. .
3. Clark’s/ dorsal nucleus
 situated at the base of the posterior gray column in
the thoracic & upper lumbar region only
The cells are associated with proprioceptive impulses
Its axons ascend in the lat. column of the same side
forming the posterior spinocerebellar tract

25. II. Nuclei of the anterior horn (motor)
are grouped into 3 groups of motor nuclei
1. Medial group:
 ventromedial & dorsomedial nuclei - found in all
segments of the spinal cord
 responsible for innervating the skeletal muscles of the
neck & trunk.

26. . Nuclei of the anterior horn cont…d
2. Lateral group:
 ventrolateral & dorsolateral nuclei - present in the cervical
& lumbosacral segments of the cord & responsible for
innervating the skeletal muscles of the limbs
3. Central group:
 present in some cervical & lumbosacral segments
 phrenic nucleus (C3-C5 segments) – efferents supplying
the diaphragm
 accessory nucleus (C1-C5/6 segments)

27. III. Nuclei of the lat. horn (autonomic)
Formed by the intermediolateral group of cells
1) Sympathetic
Present in the lat. horns of the segment from T1 to
L2/3
its axons leave the cord through the ventral roots of
the corresponding nerves as preganglionic fibers
2) Parasympathetic
Present in the lat. horn of the S2,3,&4 spinal segments
give rise to preganglionic parasympathetic fibers
which relay in peripheral ganglia in the organ supplied

28. B. White Matter
 It is divided into 3 large columns on each side
 Posterior column: lies b/n the post median septum & the
attachment of the dorsal nerve root
 it contains ascending tracts only
 Lateral column: lies b/n the attachments of the dorsal &
ventral nerve roots.
 It contains both ascending & descending tracts.
 Anterior column: lies b/n the ant. median fissure & the
attachment of the ventral nerve roots.
 It contains descending tracts mainly.

29. .

30. PATHWAYS IN WHITE MATTER
 the white matter contains 3 types of nerve fibres
 Ascending (sensory) tracts: carrying sensory impulses
from the spinal cord to higher centers
 Descending or efferent tracts: carrying motor or
autonomic impulses from higher centres to the spinal
cord.
 Associative tracts: containing short ascending &
descending fibres which coordinate the function of the
different regions of spinal cord

31. Descending tracts
Function
 maintenance of posture and balance,
 control of visceral and somatic reflex activity and
muscle tone
 modification of the sensory signals

32. Descending Fiber Systems
Upper Motor Neurons
 Are the nerve fibers that descend in the white matter
from different supraspinal nerve centers
 provide numerous separate pathways that can
influence motor activity.
Lower Motor Neurons
 Are the motor neurons situated in the anterior gray
columns of the spinal cord sending axons to innervate
skeletal muscle
 constitute the final common pathway to the muscles.

33. ,
Descending pathway
A. Corticospinal Tract
 Arises from the cerebral cortex
Pathways
 is a large bundle of myelinated axons that
descends through the brain stem via a tract called
the medullary pyramid and then largely crosses
over downward into the lateral white columns.

34. .
 The great majority of
axons in the
corticospinal system
decussate in the
pyramidal decussation
within the medulla and
descend within the
lateral corticospinal
tract
 These fibers terminate
throughout the ventral
gray column and at the
base of the dorsal
column.

35. Corticospinal tracts

36. .
Function of cortico-spinal tract
- concerned with voluntary, discrete, skilled movements,
especially those of the distal parts of the limbs
B. Rubrospinal tract:
 Arises from the red nucleus & crosses to the opposite side
 Descends in the lat. column of the spinal cord
Function:
 relays impulses from the corpus striatum & cerebellum to
the A.H.Cs of the spinal cord
 facilitates the activity of flexor muscles & inhibits the
activity of extensor or antigravity muscles

37. Rubrospinal tract

38. .
C. Tectospinal Tract:
 Arises from the sup. colliculus of midbrain
 Crosses to the opposite side
 Descends in the ant. column of the spinal cord
Function
 concerned with reflex postural movements in response to
visual stimuli

39. Tectospinal tract

40. .
D. Vestibulospinal Tract
 Arises from the lat-vestibular nucleus in the pons
 majority of its fibres are uncrossed
 Descends in the ant. column of the spinal cord
Function:
 facilitates the activity of the extensor muscles, inhibits
the activity of the flexor muscles, & is concerned with
the postural activity associated with balance.

41. Vestibulospinal tract

42. Ascending tracts of the spinal cord
Anatomical organization
 General information from the peripheral sensory endings is
conducted through the nervous system by a series of
neurons.
 The ascending pathway to consciousness consists of a three
neuron chain:
1. The first-order neuron
 has its cell body in the posterior root ganglion of the
spinal nerve.
 A peripheral process connects with a sensory receptor
ending, whereas a central process enters the spinal cord
through the posterior root to synapse on the second-order
neuron.

43. .
2. The second-order neuron
 gives rise to an axon that decussates & ascends to
a higher level of the central nervous system,
where it synapses with the third-order neuron
3. The third-order neuron
 is usually in the thalamus & gives rise to a
projection fiber that passes to a sensory region of
the cerebral cortex

44. Simplest form of the ascending sensory pathway from the sensory
nerve ending to the cerebral cortex

45. Ascending Pathways
1.Lateral Spinothalamic Tract
The pain and thermal receptors in the skin and
other tissues are free nerve endings.
Painful and thermal sensations ascend in the
lateral spinothalamic tract

46. Pain & temperature pathways

47. .
2.Anterior Spinothalamic Tract
The axons enter the spinal cord from the posterior
root ganglion and proceed to the tip of the
posterior gray column where they divide into
ascending and descending branches
these fibers of the first-order neuron terminate by
synapsing with cells in the substantia gelatinosa
group in the posterior gray column
Transmit impulses from light touch & pressure
receptor

48. .
Light/crud
e touch &
pressure
pathways

49. .
3. posterior White Column:
Fasciculus Gracilis and Fasciculus Cuneatus
The axons enter the spinal cord from the posterior
root ganglion and pass directly to the posterior
white column of the same side.
Here, the fibers divide into long ascending and
short descending fiber
 these short descending fibers are involved with
intersegmental reflexes
For discriminative Touch, Vibratory Sense, and
Conscious Muscle Joint Sense

50. ..
Many of the long ascending fibers travel upward in the
posterior white column as the fasciculus gracilis and
fasciculus cuneatus.
The fasciculus gracilis is present throughout the
length of the spinal cord and contains the long
ascending fibers from the sacral, lumbar, and lower six
thoracic spinal nerves.
The fasciculus cuneatus contains the long ascending
fibers from the upper six thoracic and all the cervical
spinal nerves.

51. .
The fibers of the fasciculus gracilis and fasciculus
cuneatus ascend ipsilaterally
 terminate by synapsing on the second-order
neurons in the nuclei gracilis and cuneatus
The axons of the second-order neurons decussate
with the corresponding fibers of the opposite side
in the sensory decussation.
The fibers then ascend as a single compact bundle,
the medial lemniscus, through the medulla
oblongata, the pons, and the midbrain

52. .
 Many fibers in the fasciculus cuneatus from the
cervical and upper thoracic segments, having
terminated on the second-order neuron of the
nucleus cuneatus, are relayed and travel as the
axons of the second-order neurons to enter the
cerebellum.
 The pathway is referred to as the cuneocerebellar
tract

53. .
4. Posterior Spinocerebellar Tract
 The axons enter to the posterior gray column and
terminate by synapsing on the second-order neurons
at the base of the posterior gray column.
 The axons of the second-order neurons enter the
posterolateral part of the lateral white column on the
same side and ascend as the posterior spinocerebellar
tract to the medulla oblongata.
 Here, the tract joins the inferior cerebellar peduncle
and terminates in the cerebellar cortex
 to transmite muscle and Joint Sense impulse to the
Cerebellum

54. .
 The posterior spinocerebellar fibers receive muscle
joint information from the muscle spindles,
tendon organs, and joint receptors of the trunk
and lower limbs.

55. .
5.Anterior Spinocerebellar Tract
 The axons terminate by synapsing with the second-order
neurons in the nucleus dorsalis at the base of the posterior gray
column .
 The majority of the axons of the second-order neurons cross to
the opposite side
 ascend as the anterior spinocerebellar tract in the contralateral
white column;
 the minority of the axons ascend as the anterior spinocerebellar
tract in the lateral white column of the same side .
 enter the cerebellum through the superior cerebellar peduncle

56. Unconscious muscle joint sense pathways to the cerebellum.

57. Anatomy of the ventricle
1. Lateral Ventricles
 There are two large lateral ventricles, and one is
present in each cerebral hemisphere.
 may be divided into a body, which occupies the
parietal lobe and from which anterior, posterior,
and inferior horns extend.

58. .

59. .

60. .
-The body of the lateral
ventricle extends from the
interventricular foramen
posteriorly as far as the
posterior end of the
thalamus.
The body of the lateral
ventricle has a roof, a floor,
and a medial wall
The roof - undersurface of
the corpus callosum .
The floor - the body of the
caudate nucleus and the
lateral margin of the
thalamus
The medial wall- septum
pellucidum

61. .
Choroid Plexus of the Lateral Ventricle
 projects into the ventricle on its medial aspect
 is a vascular fringe composed of pia mater covered with
the ependymal lining of the ventricular cavity.
 The blood supply of the choroid plexuses is derived
from the choroidal branches of the internal carotid
and basilar arteries.
 The venous blood drains into the internal cerebral
veins=> the great cerebral vein=> joins the inferior
sagittal sinus to form the straight sinus.

62. .
coronal section of
the third and
lateral ventricles at
the site of the
interventricular
foramina showing
the structure of the
tela choroidea and
its relationship
with the ependyma
and pia mater

63. .
2. Third Ventricle
 is a slitlike cleft between the two thalami.
 It communicates
- anteriorly with the lateral ventricles and
- posteriorly with the fourth ventricle
Boundary
The anterior
- a thin sheet of gray matter, the lamina terminalis
and ant. commissure

64. .
The posterior wall
 is formed by the opening into the cerebral aqueduct.
 Superior to this opening is the small posterior
commissure
The lateral wall
 is formed by the medial surface of the thalamus
superiorly and the hypothalamus inferiorly
The superior wall
 is formed by a layer of ependyma that is continuous
with the lining of the ventricle

65. .
The inferior wall
 is formed by the optic chiasma, the tuber
cinereum, the infundibulum and the mammillary
bodies

66. Sagittal section of the brain showing the medial surface
of the diencephalon

67. .
3. Fourth Ventricle
is a tent-shaped cavity filled with cerebrospinal fluid.
is situated anterior to the cerebellum and posterior to
the pons and the superior half of the medulla
oblongata.
It is lined with ependyma
 The fourth ventricle possesses:
- lateral boundaries
- a roof
- rhomboid-shaped floor.

68. .
Lateral Boundaries
 The caudal part by the inferior cerebellar
peduncle and the cranial part by the superior
cerebellar peduncle.
Posterior Wall
 The tent-shaped roof projects into the cerebellum.
The superior part is by the medial borders of the
two superior cerebellar peduncles and the superior
medullary velum

69. .
 The inferior part of the roof is formed by the
inferior medullary velum
Floor
 is formed by the posterior surface of the pons and
the cranial half of the medulla oblongata

70. .

71. Cerebrospinal Fluid
 The cerebrospinal fluid is found in the ventricles
of the brain and in the subarachnoid space around
the brain and spinal cord

72. The Physical Characteristics and Composition of the
Cerebrospinal Fluid

73. .
Functions of CSF
serves as a cushion between the central nervous
system and the surrounding bones, thus
protecting it against mechanical trauma.
it provides mechanical buoyancy and support for
the brain.
 assist in the regulation of the contents of the
skull.

74. .

75. .
Formation of CSF
 The cerebrospinal fluid is formed mainly in the
choroid plexuses of the lateral, third, and fourth
ventricles
 production of cerebrospinal fluid is not pressure
regulated

76. .
Circulation of CSF
 The circulation begins with its secretion from the
choroid plexuses in the ventricles.
 aided by the arterial pulsations of the choroid
plexuses and by the cilia on the ependymal cells
lining the ventricles.

77. .
Absorption of CSF
 The main sites are the arachnoid villi that project
into the dural venous sinuses
 The arachnoid villi tend to be grouped together to
form elevations known as arachnoid granulations.
 Structurally, each arachnoid villus is a
diverticulum of the subarachnoid space

78. .

79. summary
 SP. cord stretches from upper border of the
foramen Magnum to the intervertebral disc
between the first and second lumbar vertebrae
and occupy 2/3 of upper vertebra
 is invested by the dura, arachnoid, and the pia
mater
 Both pia and arachnoid mater form the
leptomeninges, and they continue around the
spinal nerves as perineurium

80. Summary cont…d
 Three longitudinal arteries supply the spinal cord
 The veins draining the spinal cord join the internal
vertebral venous plexus in the epidural space
 Each spinal segment consists of central gray and
peripheral white matters
 the white matter contains 3 types of nerve fibres
 Painful and thermal sensations ascend in the
lateral spinothalamic tract

81. Summary cont…d
 Light (Crude) Touch and Pressure sensation
ascend through ant. Spinothalamic tract
 Discriminative Touch, Vibratory Sense, and
Conscious Muscle Joint Sense passes through
dorsal column
 The ventricles are four fluid-filled cavities located
within the brain

82. Summary cont…d
 The cerebrospinal fluid is formed mainly in the
choroid plexuses of the lateral, third, and fourth
ventricles by active process
 CSF absorption is based on pressure gradient

83. References
1. CLINICAL NEUROANATOMY ,BY SNELL, 7TH
EDITION
2. CLINICAL NEUROANATOMY BY STEPHEN G.
WAXMAN, 25TH EDTION
3. NEUROANATOMICAL BASIS OF CLINICAL
NEUROLOGY,by Orhan Arslan
4. MOORE, CLINICALLY ORIENTED ANATOMY,
5TH EDITION
5. GUYTON TEXTBOOK OF MEDICAL
PHYSIOLOGY, 11th edi

84. .
Thank you