1. Spinal cord External features

2. Objectives Describe the gross anatomical features of the spinal cord.
Describe the level of the different spinal segments comparing to the level of their respective vertebrae.
Identify important gross features of spinal cord, nerve roots, and spinal ganglia.
Describe the internal features of spinal cord (gray matter and white matter) in the different regions.

3. Structure of the Spinal Cord
A cylinder of gray & white matter
In the upper 2/3 of vertebral canal
Extends From foramen magnum to L1 (or L2)
Covered with meninges & CSF
A typical adult spinal cord ranges between 42 and 45 centimeters .

4. The spinal cord is associated with 31 pairs of spinal nerves that connect the CNS to muscles, receptors, and glands.
Each side of the spinal cord contains :
8 cervical nerves (called C1–C8),
12 thoracic nerves (T1–T12),
5 lumbar nerves (L1–L5),
5 sacral nerves (S1–S5),
and 1 coccygeal nerve

5. Structure of the Spinal Cord
The spinal cord is shorter than the vertebral canal that houses it. Extends only to L1/ L2
Has two enlargements, cervical & lumbar due to cells and fibers of limbs.
Ends inferiorly in a tapering
conus medullaris
Anchored to the coccyx by
a meningeal ( non neuronal) extension (filum terminale)
Held to dura by denticulate
ligament

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7. The Spinal Cord
Provides a vital link between the brain and the rest of the body.
Exhibits some functional independence from the brain.
The spinal cord and its attached spinal nerves serve some important functions :-

8. Functions of the Spinal Cord
Receives afferent fibers from sensory receptors of the trunk and limbs
Controls movements of the trunk and limbs
Provide autonomic innervation for most of the viscera.
Responsible for many loop reflexes
It conveys afferent information to higher centers and mediate their controlling influence over spinal mechanisms.

9. Spinal Meninges Are continuous with the cranial meninges.
Structures that encircle the spinal cord, listed from outermost to innermost are:
1-vertebra
2-epidural space: Contains blood vessels, areolar connective tissue and fat.
3-dura mater
4-subdural space: a potential cavity between the dura and arachnoid mater, contains a small volume of serous fluid
5-arachnoid
6-subarachnoid space: Contains cerebrospinal fluid (CSF) and blood vessels
7-pia mater

12. The cervical enlargement
consists of cord segments
C3-T1 and provides innervation for the upper limb via the brachial plexus.
The lumbar enlargement is
made up of segments L1-S3
and is associated with
innervation of the lower limb
via the lumbar plexus (L1-L4)
and the sacral plexus (L4-S2)

13. Surfaces Surface marked by furrows A deep ventral (anterior)
median fissure
A dorsal (posterior)
median sulcus
2 dorsolateral &
2 ventrolateral sulci
2 dorsal intermediate sulci

14. Cross Section of Spinal Cord
Anterior median fissure and posterior median sulcus
deep clefts partially separating left and right halves
Gray matter: neuron cell bodies, dendrites, unmylinated axons
Divided into horns
Posterior (dorsal) horn
Anterior (ventral) horn
Lateral horn

16. White matter
Myelinated axons
Divided into three columns (funiculi)
Ventral
Dorsal
lateral
Each of these divided into sensory or motor tracts
Commissures: connections between left and right halves
Gray with central canal in the center
White
Roots
Spinal nerves arise as rootlets then combine to form dorsal and ventral roots
Dorsal and ventral roots merge laterally and form the spinal nerve

17. Grey matter
Consists of nerve cell bodies and their processes, neuroglia, and blood vessels
The nerve cells are multipolar and are of three main categories:
Sensory neurons (Tract cells), which receive impulses from the periphery of the body and whose axons constitute the ascending fasciculi of the white matter, are located in the dorsal horns
Lower motor neurons, which transmit impulses to the skeletal muscles, are located in the ventral horns (similar neurons in the lateral horn are the preganglionic neurons of the autonomic system)
Interneurons (connector neurons) : linking sensory and motor neurons, at the same or different levels, which form spinal reflex arcs.

18. Different cord levels vary in
the relative amounts and
configuration of grey and
white matter.
Higher levels contain greater
amounts of white matter.
Why?
Because ascending tracts gain
fibres at each successive level,
whereas the opposite is true
of descending tracts.

19. The size and shape of the dorsal
and ventral horns varies according
to the level.
Both dorsal and ventral horns are,
therefore, particularly well developed at cervical and lumbar levels in association with innervation of the upper and lower limbs.

20. The Gray Matter Contain categories of neurons:
The smallest interneurons
Motor neurons of ventral horn (large  & smaller )
Lateral horns contain autonomic neurons
Tract (or relay) cells in dorsal horn (related to sensory system)

21. Gray Matter The grey matter of the spinal cord
may be divided, on the basis of its
cytoarchitecture, into ten zones,
known as Rexed's laminae, which
are numbered sequentially from
dorsal to ventral.
Some of these laminae are equated
with cell groupings of particular
functional types.

22. Corresponding nucleus
Gray Matter
Corresponding nucleus
Lamina I II
III & IV V VI
VII
VIII IX
Posteromarginal nucleus
Substantia gelatinosa
Nucleus properius
Zone anterior to lamina IV
Zone at base of posterior horn
Zona intermedia
Zone in anterior horn
Medial nuclear column and lateral nuclear column

23. The White matter 3 columns or funiculi (ventral, Dorsal, Lateral)
Mainly of myelinated axons
Form definite functional tracts (fasciculi)
The sensory ones are the ascending tracts.
The motor ones are the descending tracts.

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27. Thank you