B ANATOMY, NEUROPATHOLOGY AND REGENERATION
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Ligamentum denticulatum
In the cervical and thoracic regions the arachnoid thickens between the anterior and
posterior roots and on each side forming the ligamentum denticulatum through a tooth-
like process which is fixed to the innerside of the dura. There are 20 denticulate ligaments
in the cervical and thoracic regions, the last being at the level of the i2th thoracic and
first lumbar spinal roots.
The pia mater covers the whole spinal cord and is firmly adherent to it and also lines
the wall of the anterior median fissure. Below the conus medullaris the pia is continued
as filum terminale. Fig. 22 demonstrates the relationship of the spinal cord to its meninges.
Inner structure
The spinal cord is divided into the grey and white matter, the latter surrounding the
grey substance.
The grey matter
The grey matter, substantia grisea, runs throughout the whole length of the spinal cord
and forms a column which on cross section has the shape of a butterfly and consists of
anterior, lateral and posterior horns. The two symmetrical columns of the grey matter
are connected by a bridge of the intermediate central substance, containing in the middle
the central canal which is surrounded by the substantia gelatinosa centralis. The central
canal containing cerebro-spinal fluid runs through the cord caudally to the conus
terminalis and partly the filum terminale and continues cephalad through the distal part
of the oblongata into the 4th ventricle. Transverse sections through the spinal cord at
various levels show considerable differences in shape and extent of the grey matter, and
in the cervical and lumbar enlargement and also sacral cord it takes a large space as
compared with the upper cervical and thoracic regions (Fig. 23).
HISTOLOGICAL STRUCTURES
One has to distinguish between neuronal and supporting tissues. The neurones have their
cell bodies in the grey matter sending out long axons. There are receptor, effector and
connector (internuncial) neurones. Neurones and their dendrites are linked with other
neurones by synapses, a Greek term
O-VVOCTTTO):
to clasp introduced by Sherrington
(1897) to explain the transverse membranes which separate two neurones at close
contiguity. In the grey of the anterior column the ganglion cells which are multipolar
and their axons representing the 'final common motor path', innervate the striated muscles,
some of them, specifically, the neuromuscular bundles, through the intrafusal fibres.
The number of synapses connected with the effector cells of the anterior grey column
is particularly large.
Receptor neurones consist of bipolar or pseudo-unipolar nerve cells, while the inter–
nuncial neurones are, like the effector neurones, multipolar.
