Download M555 Medical Neuroscience Cervical Thoracic Lumbar Sacral

M555 Medical Neuroscience
Lab 2: The Spinal Cord
OBJECTIVES
1. Recognize cervical, thoracic, lumbar and sacral levels of the spinal cord.
2. Be able to name and locate major structures in the spinal cord.
3. Recognize major nuclei and tracts in the spinal cord.
4. Know basic spinal cord anatomy in order to localize lesions in the spinal cord
and to know the outcomes resulting from spinal cord lesions.
NOTES
1. Spinal cord slides will be available in lab for several weeks. January 11th and 13th,
the open lab on January 20th and during the first Brain Stem Lab on January 25th and 27th.
2. Digital images of spinal cord sections can also be accessed on line:
medsci.indiana.edu/m555/index.html
SPINAL CORD STRUCTURES
Gross Anatomy
Spend a few minutes looking at a spibnal cord to see these structures:
spinal cord enlargements (cervical and lumbar)
conus medullaris
cauda equina
spinal nerves
dorsal roots
dorsal root ganglions
ventral roots
brain
Cervical
Nerves
enlargement
dorsal columns
gracile fasciculus
cuneate fasciculus
Three Questions
What might explain the Cervical
and Lumbar enlargements compared
to the narrower Thoracic cord?
Why are the lower Lumbar and Sacral
Spinal Nerves (in the Cauda Equina)
so long ?
Why is it an over-simplification
to say that each spinal level
has one dorsal and one ventral root
on each side of the cord?
spinal cord
Thoracic
Nerves
Lumbar
Nerves
Sacral
Nerves
enlargement
conus
medularis
cauda equina
Compare the size amd the relative amounts of gray and white matter at the four levels of the spinal
cord so that you can identify the spinal level( cervical, thoracic, lumbar or sacral)
when shown a cross-section of the cord.
Here are cross-sections several cervical, thoracic and lumbar levels, along with one sacral leve,
that allow comparisons of the four major levels of th espinal cord.l
cervical 3
thoracic 10
cervical 5
cervical 8
lumbar 2
lumbar 5
thoracic 5
sacral 4
Nolte, figure 10-6
How do the absolute sizes (particularly the widths) of the spinal sections change
from level to level?
How do the relative amount of gray matter to white matter of the spinal sections change
from level to level?
What might explain these differences?
At what levels can a lateral horn of the spinal gray matter be seen?
(see the Microscopic Anatomy section for more information on the Lateral Horn)
Microscopic Anatomy
central canal
gray matter
dorsal horn
substantia gelatinosa
dorsolateral tract (Lissauer’s Fasciculus)
intermediolateral gray column (thoracic and upper lumbar levels)
nicknamed “the lateral horn”
location of the Dorsal Nucleus of Clarke (thoracic and upper lumbar levels)
ventral (anterior) horn
large motor neurons in the ventral gray matter
white matter
dorsal median sulcus
dorsal funiculus
dorsal columns
gracile fasciculus
(all levels of spinal cord)
cunate fasciculus
(above thoracic 5)
lateral funiculus and ventral funiculus
location of corticospinal tract
location of anterolateral system (a major pain and temperature pathway)
anterior (ventral) white commissure
LARGE Multipolar Neurons in the Anterior Horn
location: one or more locations in anterior (ventral) horn
of spinal cord gray matter
present at all spinal cord levels, but ...
particularly numerous at the level
of the cervical and lumbar enlargements
significance: innervate skeletal muscles
axons of these cells form the ONLY link
between the CNS and skeletal muscle cells
also known as: Somatic Motor Neurons
Alpha Motor Neurons
Lower Motor Neurons
Central Canal
location: in the center of the spinal gray matter
significance: vestige of the hollow core of the neural tube
note: inner surface lined by ependymal cells
(like all surfaces that border a ventricular space
in the brain)
digital images may be found at
medsci.indiana.edu/m555/index.html
Anterior White Commissure (AWC)
commissure: a term for a bundle of axons that cross the midline
of the CNS
location: just anterior (ventral) to the Central Canal of the spinal cord
significance: axons of spinal cord neurons
that carry pain and temperature information
pass through the AWC
cervical spinal cord
low thoracic level
thoracic spinal cord
Dorsal Columns (DCs)
location: dorsal (posterior) white mater of the spinal cord
significance: axons of primary sensory neurons that carry
fine touch,
low thoracic
level proprioceptive and vibration sense
up to the lower medulla form the DCs
composition: two “columns” of axons on each side GRACILE FASCICULUS (more medial)
at all levels of the spinal cord
CUNEATE FASCICULUS (more lateral)
at levels of the spinal cord above Thoracic 5
fasciculus: a term for axons gathered together in a bundle
Dorsal Nucleus of Clarke (“Clarke’s Nucleus”)
location: in the medial gray matter at the base of the dorsal horn
of spinal levels Thoracic 1 – Lumbar 3
significance: contains cell bodies of neurons whose axons
form the posterior spinocerebellar tract an important source of input to the cerebellum
low thoracic level
Lateral Horn of Spinal Cord Gray Matter
more formally known as the Intermediolateral Column
location: lateral margin of gray matter
at spinal levels Thoracic 1 – Lumbar 3
the Lateral Horn and Clarke’s Nucleus
are located at the same spinal levels,
but they have nothing to do with one another
significance: contains the cell bodies
of preganglionic sympathetic neurons
Dorsolateral Fasciculus (DF)
Lissauer’s Tract
location: tip of dorsal horn at all spinal levels
significance: entrance point for thin-diameter sensory axons,
including “pain and temperature fibers”
these axons may run up or down in DF
several spinal levels before terminating
on neurons in the dorsal horn
fasciculus: a term for axons gathered together in a bundle
cervical spinal cord
cervical spinal cord
Substantia Gelatinosa
location: posterior part of dorsal horn gray matter
at all levels
low thoracic
level of the spinal cordlow thoracic level
significance: incomming pain and temperature information
crosses synapses here
note: clearer appearance - gelatinous name