01
Spinal cord

  • is a long, narrow cylindrical structure- 45-50cm
  • diameter-2cm
  • lies outside the skull
  • begins at base of skull- the foremen magnum
  • terminates at lower border of 1st lumbar vertebra L1
  • below L1 the spinal cord contains the lumbar & sacral roots in bands- the cauda equina.( the horse tail)

Cross section

Anterior median fissure

A prominent fissure anteriorly

Posterior median fissure/septum

A less prominent fissure posteriorly

Central canal

What lies between these fissures

H shaped figure

Grey matter consisting of nerve cells

Dorsal horns

  • Posterior
  • long & narrow

Ventral horns

  • Ventral
  • thick & broad

Horizontal stem of H

Constitutes the grey matter
( ant & post)
which surrounds the
central canal

Contains cell bodies of

  • alpha
  • gamma &
  • renshaw motor neurons

Axons of alpha & motor neurons
pass out into the ventral roots

These fibers are
Purely motor in function

Recieves
the fibers of
the posterior roots

Is purely sensory in function :

Their cell bodies are found in the
Dorsal root ganglion
( a swelling on the posterior root)

These ganglion cells are
bipolar
meaning
their Axons connect with both the
dorsal & ventral horn structures

SENSORY

MOTOR

White matter

Surrounding the H
Of grey matter
is the white matter

Consists of many
ascending & descending axons
cut across it

Divided into 3 white columns
funiculi

Anterior
white column

Lateral
white column

Dorsal
white column

Lie betw the
anterior median fissure
&
anterior roots

Lie betw the
anterior roots
&
posterior roots

Lie betw the
posterior roots
&
posterior median fissure

Mixed nerve)

The sensory & motor fibers
join to form
a mixed nerve

Which comes out from the
vertebral canal as a
peripheral spinal nerve
via the
intervertebral foremen

Ventral horn motor neurons
show an orderly topographical
arrangement within the spinal cord

Medially

Motor neurons
supplying
the muscles of

  • proximal limb
  • trunk

Laterally

Motor neurons
supplying
the muscles of

  • the distal limb

Dorsally/
posteriorly

Motor neurons
supplying
the muscles that

Flex the limbs
flexors

Ventrally/
Anteriorly

Motor neurons
supplying
the muscles that

Extend the limbs
extensors

  • Medially- proximal limb + trunk
  • laterally- distal limb
  • posteriorly - flexors
  • anteriorly - extensors

Intermediate horn

Lies in between the
dorsal & ventral horns

Contains cell bodies of
autonomic neurons
( sympathetic division)

These only extend
between
T1 to L2 segment

In brain stem & spinal cord

White matter
surrounds
grey matter

In the cerebrum & cerebellum

Grey matter
surrounds
white matter

Myelin

Gives white appearance

Cell bodies

Gives grey appearance