2. Spinal cord

3.  The spinal cord provides a crucial information
conduit, connecting the brain with most of
the body.
 It is the target of a number of disease
processes, some of which (eg, spinal cord
compression) are treatable but rapidly
progressive if not treated.

4.  Failure to diagnose some disorders of the
spinal cord, such as spinal cord compression,
can be catastrophic and may relegate the
patient to a lifetime of paralysis.
 A knowledge of the architecture of the spinal
cord and its coverings, and of the fiber tracts
and cell groups that comprise it, is essential.

9.  The sensory component of each spinal nerve
is distributed to a dermatome, a well-defined
segmental portion of the skin
 in many patients there is no C1 dorsal root,
there is no C1 dermatome
 when a C1 dermatome does exist as an
anatomic variant, it covers a small area in the
central part of the neck, close to the occiput

10.  dermatomes for C5, C6, C7, C8, and T1 are
confined to the arm
 C4 and T2 dermatomes are contiguous over
the anterior trunk.
 thumb, middle finger, and fifth digit are
within the C6, C7, and C8 dermatomes,
respectively

11.  Nipple-T4
 Umbilicus – T 10

12.  The territories of dermatomes tend to
overlap, making it difficult to determine the
absence of a single segmental innervation on
the basis of sensory testing

14. Myotomes
 myotome refers to the skeletal musculature
innervated by motor axons in a given spinal
root
 Most muscles are innervated by motor axons
that arise from several adjacent spinal roots.
 Nevertheless, lesions of a single spinal root, in
many cases, can cause weakness and atrophy
of a muscle

15. Segment-Pointer Muscles.
Root Muscle
 C5  Deltoid
 C5  Biceps
 C6  Brachioradialis
 C7
 Triceps
 Quadriceps femoris
 L3, L4
 Extensor hallucis
 L5 longus
 S1  Gastrocnemius

26. Rexed’s laminae

28. Rexed's laminae
 Lamina I
 This thin marginal layer contains neurons that
respond to noxious stimuli [pain,
temperature] and send axons to the
contralateral spinothalamic tract.

29.  Lamina II- substantia gelatinosa
 made up of small neurons, some of which
respond to noxious stimuli.
 Substance P, a neuropeptide involved in
pathways mediating sensibility to pain, is
found in high concentrations in laminas I and
II.

30.  Laminas III and IV
[nucleus proprius]
Their main input is from fibers that convey
position and light touch sense.
 Lamina V
contains cells that respond to both noxious and
visceral afferent stimuli.

31.  Lamina VI
 deepest layer ,contains neurons that respond
to mechanical signals from joints and skin.

32. Lamina VII
 contains the cells of the dorsal nucleus
(Clarke's column) medially as well as a large
portion of the ventral gray column.
 Clarke's column contains cells that give rise to
the posterior spinocerebellar tract.

33.  also contains the intermediolateral nucleus
(or intermediolateral cell column) in thoracic
and upper lumbar regions.
 Preganglionic sympathetic fibers project
from cells in this nucleus, via the ventral roots
and white rami communicantes, to
sympathetic ganglia.

34. Laminas VIII and IX
 represent motor neuron groups in the medial
and lateral portions of the ventral gray
column
 The medial portion (also termed the medial
motor neuron column) contains the LMNs
that innervate axial musculature

35.  The lateral motor neuron column contains
LMNs for the distal muscles of the arm and
leg
 flexor muscles are innervated by motor
neurons located close to the central canal
 extensor muscles are innervated by motor
neurons located more peripherally

36. Lamina X
 represents the small neurons around the
central canal or its remnants.

38. White Matter
 composed of myelinated and unmyelinated
nerve fibers.
 The fast-conducting myelinated fibers form
bundles (fasciculi) that ascend or descend for
varying distances
 Fiber bundles with a common function are
called tracts

39.  The lateral and ventral white columns contain
tracts that are not well delimited and may
overlap in their cross sectional areas
 the dorsal column tracts are sharply defined
by glial septa

40. Location of tracts

41. Descending tracts in the Spinal
Cord.
 Lateral corticospinal  Fine motor function
(pyramidal) tract (controls distal
musculature)
Modulation of
sensory functions

43.  Anterior  Gross and postural
corticospinal tract motor function
(proximal and axial
musculature
 Vestibulospinal tract  Postural reflexes

44.  Rubrospinal  Motor function
 Reticulospinal  Modulation of
sensory
transmission
(especially pain)
Modulation of spinal
reflexes

45.  Descending  Modulation of
autonomic autonomic
functions
 Tectospinal  Reflex head turning
 Medial longitudinal  Coordination of
fasciculus head and eye
movements

46. Ascending tracts
 Dorsal column  Fine touch,
system proprioception,
two-point
discrimination
 Spinothalamic
tracts  Sharp pain,
temperature, crude
touch

47.  Dorsal spinocerebellar  Movement and
tract position mechanisms
 Ventral spinocerebellar  Movement and
position mechanisms