The document provides a comprehensive overview of the spinal cord, including its structure, function, and major ascending tracts. Key features discussed include the spinal cord's external anatomy, meningeal coverings, and internal organization into grey and white matter. It also highlights various ascending tracts responsible for sensory information, such as the spinothalamic and dorsal column tracts.

1. Spinal Cord (1)
Introduction and Ascending Tracts
By: Ahmed A. E. Eljack

2. Is it really important?
2

3. Objectives:
3
By the end of this session you should be able to:
● Describe the spinal cord, its location and its
function.
● Describe the surface features of the spinal cord
and its meningeal coverings.
● Discuss the internal structure of the spinal
cord.

4. Objectives:
4
● List the major ascending tracts in the spinal
cord and their functions.
● Describe the pathways of each major
ascending tract.
● Discuss other minor ascending tracts and their
functions.

5. External Anatomy of the Spinal
Cord
5

6. Surface Features
● The spinal cord extends from the foramen
magnum (medullary spinal junction) to the first
or second lumbar vertebra.
● It occupies the upper two thirds of the vertebral
column.
● The rest of the cord is occupied by cauda
equina.
6

7. 7
Haines, Duane. Fundamental Neuroscience For Basic
And Clinical Applications. 4th ed. Philadelphia:
Elsevier, 2013. Fig. 9-2 (cropped)

8. ● The spinal cord is divided to:
○ Cervical spinal cord (8 pairs of nerves).
○ Thoracic spinal cord (12 pairs of nerves).
○ Lumbar spinal cord (5 pairs of nerves).
○ Sacral spinal cord (5 pairs of nerves).
○ Coccygeal spinal cord (1 pair of nerves).
Surface Features
8

9. 9
Surface Features
● The spinal cord is enlarged at the cervical and
lumbosacral parts to give the origin to the
brachial and lumbosacral plexuses,
respectively.
● It ends into the conus medullaris.

10. 10
Purves, D., Augustine, G., Fitzpatrick, D., Hall, W.,
LaMantina, A. and White, L. (2012). Neuroscience. 5th
ed. Sunderland: Sinauer Associates, Inc. Fig. A5 (A)

11. 11
Surface Features
● The anterior median fissure is a deep
longitudinal fissure in the anterior surface.
● The posterior median sulcus is a shallow sulcus
in the posterior surface. It contains the posterior
median septum (pia mater).

12. 12
Surface Features
● The posterolateral sulcus is the entry site for
the posterior root (sensory) fibers.
● The anterolateral sulcus is the exit site for the
anterior root (motor) fibers.

13. 13
Eljack’s Lecture Notes in Neuroscience. Fig. 3-4
©2015 all rights reserved

14. 14
Eljack’s Lecture Notes in Neuroscience. Fig. 3-3
©2015 all rights reserved

15. 15
Meningeal Covering
● The spinal cord is covered by:
○ Dura mater
○ Arachnoid mater
○ Pia mater
● Filum terminale is a prolongation of the pia mater
from the apex of the conus medullaris to the
posterior surface of the coccyx.

16. 16
Meningeal Covering
● The subarachnoid space at the level of the
cauda equina enlarges to form the lumbar
cistern (site for lumbar puncture and spinal
anesthesia).
● The pia mater attaches to the vertebral column
laterally by the denticulate ligament.

17. 17
Haines, Duane. Fundamental Neuroscience For Basic
And Clinical Applications. 4th ed. Philadelphia:
Elsevier, 2013. Fig. 9-2 (cropped)

18. 18
Internal Anatomy of the Spinal
Cord

19. 19
The inner core of the spinal cord is
formed by grey matter and it is
surrounded by white matter

20. Grey Matter
20
● Composed of neuronal cell bodies, dendrites,
initial parts of axons, and glial cells.
● Divided into dorsal (posterior) and ventral
(anterior) horns (H shape in cross sections).
● The grey commissure connects the anterior and
posterior horns. It contains the central canal.

21. 21
Grey Matter
● The dorsal horn receives sensory information
while the ventral horn projects motor
commands.
● The small lateral grey horn lie in the thoracic
and upper lumbar segments. It functions as
sympathetic synapse area.

22. 22
Grey Matter
● The posterior grey horn has four nerve groups:
○ Substantia gelatinosa group (lamina II)
○ Nucleus proprius group (laminae III & IV)
○ Nucleus dorsalis group (Clarke’s column-
lamina VII)
○ Visceral afferent nucleus

23. 23
Grey Matter
● The substantia gelatinosa is located in the
apex of the posterior grey horn throughout the
spinal cord.
● It receives afferents conveying pain, touch,
and temperature.

24. 24
Grey Matter
● The nucleus proprius is located anterior to the
substantia gelatinosa throughout the spinal
cord.
● It receives afferents conveying proprioception,
two-point discrimination, and vibration from
the posterior column.

25. 25
Grey Matter
● Clarke’s column is situated at the base of the
posterior grey horn from the lower cervical to
the middle lumbar segment.
● It receives proprioceptive input (mainly muscle
and tendon spindles).

26. 26
Grey Matter
● The visceral afferent nucleus lies lateral to the
Clarke’s column from the first thoracic to the
third lumbar segment.
● It receives visceral afferent information.

27. 27
Snell, R.S. Clinical Neuroanatomy. (7th ed.). Philadelphia: Lippincott Williams &
Wilkins; 2010. Fig. 4-6 (cropped)

28. 28
Haines, Duane. Fundamental Neuroscience For Basic And
Clinical Applications. 4th ed. Philadelphia: Elsevier, 2013. Fig.
9-3

29. White Matter
29
● The white matter of the spinal cord is divided
into the following columns (funiculi):
○ Anterior column (between the midline and the
anterior nerve roots)
○ Lateral column ( between the anterior and
posterior nerve roots)

30. 30
White Matter
○ Posterior column ( between the posterior
nerve roots and the midline)
● It contains nerve axons and neuroglia along
with blood vessels.
● Each column is divided into tracts (fasciculi).
These tracts can be ascending, descending, or
intersegmental.

31. 31
Haines, Duane. Fundamental Neuroscience For Basic And
Clinical Applications. 4th ed. Philadelphia: Elsevier, 2013. Fig.
9-3

32. 32
White Matter
● The nomenclature of the tracts start with the
origin and ends with the destination.
● Ascending tracts named spino_____ tract. For
example: spinothalamic tracts.
● Descending tracts are usually named
_____spinal tract. For example: corticospinal
tract.

33. 33
Ascending Tracts of the Spinal
Cord

34. Basic Concepts
34
● Information conveyed by ascending tracts may
be divided into:
○ Exteroceptive information (pain, temperature,
and touch)
○ Proprioceptive information (e.g., muscle
stretch)

35. 35
Basic Concepts
● Each tract usually consists of three neurons:
○ First-order neuron
○ Second-order neuron
○ Third-order neuron
● Afferent axons of the first-order neurons have
their cell bodies in the dorsal root ganglia.

36. 36
Basic Concepts
● Second-order neurons decussate at different
levels.
● Third-order neurons are usually found in the
thalamus.
● These neurons branch to give input to motor
neurons and the reticular formation.

37. 37
Spinothalamic Tracts
● Also called anterolateral system.
● Consists of two tracts:
○ Anterior spinothalamic tract (crude touch)
○ Lateral spinothalamic tract (pain and
temperature)

38. 38
Spinothalamic Tracts
● They enter the spinal cord and travel for a
segment or two in the posterolateral tract of
Lissauer then synapse in lamina I, II and IV.
● After synapse, fibers from the second-order
neurons cross to the opposite side in the white
and grey commissures and travel rostrally.

39. 39
Spinothalamic Tracts
● The anterolateral system shows somatotopic
organization.
● Sensation from lower parts of the body travel
laterally while sensation from upper parts
travel medially.

40. 40
Spinothalamic Tracts
● second-order neurons synapse in the ventral
posterolateral and intralaminar thalamic
nuclei.
● Third-order neurons send axons that pass
through internal capsule to the somatosensory
cortex.

41. 41
Snell, R.S. Clinical Neuroanatomy. (7th ed.).
Philadelphia: Lippincott Williams & Wilkins; 2010. Fig.
4-13

42. 42
Eljack’s Lecture Notes in Neuroscience. Fig. 8-4
©2015 all rights reserved

43. 43
Waxman, S.G. Clinical Neuroanatomy.
(27th ed.).: McGraw-Hill; 2013. Fig. 5-16

44. 44
Dorsal Column Tracts
● Carry fine and discriminative touch, vibration,
and proprioception.
● Divided into:
○ Fasciculus gracilis (lower part of the body)
○ Fasciculus cuneatus (upper part of the body)

45. 45
Dorsal Column Tracts
● Fasciculus gracilis and cuneatus pass directly
to the ipsilateral posterior white column and
ascend without synapse till the they reach the
brainstem.
● They synapse on the nuclei gracilis and
cuneatus in the medulla oblongata,
respectively

46. 46
Dorsal Column Tracts
● Second-order neurons decussate and ascend
forming the medial lemniscus to synapse in the
ventral posterolateral nucleus of the thalamus.
● third-order neurons pass through the internal
capsule to reach the somatosensory cortex.

47. 47
Eljack’s Lecture Notes in Neuroscience. Fig. 8-3
©2015 all rights reserved

48. 48
Waxman, S.G. Clinical Neuroanatomy. (27th ed.).:
McGraw-Hill; 2013. Fig. 5-14

49. 49
Dorsal Spinocerebellar tract
● Convey proprioception and deep pressure
from the muscles to the cerebellum.
● First-order neurons synapse on Clarke’s
column.
● Fibers from the second-order neurons enter
the ipsilateral lateral white funiculus.

50. 50
Dorsal Spinocerebellar tract
● Fibers from the second-order neurons ascend
join the inferior cerebellar peduncle and
terminate in the cerebellar cortex.
● Sensory fibers from sacral and lower lumbar
travel rostrally until they meet and synapse on
the Clarke’s column.

51. 51
Anterior Spinocerebellar Tract
● Has the same function of the posterior
spinocerebellar tract in addition to sensation
from the skin.
● Axons synapse on Clarke’s column and most of
the second-order neurons decussate and
ascend to enter the cerebellum in the superior
cerebellar peduncle.

52. 52
Waxman, S.G. Clinical Neuroanatomy.
(27th ed.).: McGraw-Hill; 2013. Fig. 5-17

53. 53
Other Ascending Tracts
● Spinotectal tract (visual reflexes).
● Spinoreticular tract.
● spino -olivary tract
● Visceral sensory tracts.

54. 54
In summary...

55. 55
Further Readings
● Sinnatamby, C.S. Last's Anatomy Regional and
Applied. (12th ed.). : Churchill Livingstone;
2011.
● Snell, R.S. Clinical Neuroanatomy. (7th ed.).
Philadelphia: Lippincott Williams & Wilkins;
2010.

56. 56
Further Readings
● Eljack, A. A. E. Eljack’s Lecture Notes in
Neuroscience. Khartoum; 2015.
● Siegel, A, Sapru, H.N. Essential Neuroscience.
(3rd ed.). Philadelphia: Lippincott Williams &
Wilkins; 2015.

57. 57
Further Readings
● Medical Neuroscience MOOC by Duke
University | Coursera.
● Purves, D., Augustine, G., Fitzpatrick, D., Hall, W.,
LaMantina, A. and White, L. (2012).
Neuroscience. 5th ed. Sunderland: Sinauer
Associates, Inc.

58. 58
Further Readings
● Haines, Duane. Fundamental Neuroscience For
Basic And Clinical Applications. 4th ed.
Philadelphia: Elsevier, 2013.
● Waxman, S.G. Clinical Neuroanatomy. (26th ed.).
: McGraw-Hill; 2010.