The document summarizes the development of the spinal cord. It describes how the neural tube forms from neuroepithelial cells. The neuroepithelial cells then proliferate and form layers, including the mantle layer which contains neuroblasts and forms the grey matter, and the marginal layer containing nerve fibers which forms the white matter. It further discusses the formation of basal, alar and roof plates, and how neuroblasts in different regions form motor and sensory areas. Glial cells including astrocytes and oligodendrocytes also develop from neuroepithelial cells to support neurons.

2. 1)Neural Tube:
Wall is formed by neuroepithelial
cells(pseudost.epithelium)
2)Closure of neural tube:
Proliferation of neuroepi.cells
Form.of neuroepithelial cell layer
3)Formation of Mantle layer:
Neuroepithelial cells-Neuroblasts-
their cell bodies-GREY MATTER Of
sp.cord
4)Formation of Marginal layer:
Nerve fibres of neuroblasts-WHITE
MATTER of sp.cord

3.  Basal
 Alar
 Roof
 Floor

4.  Ventrally formed In Mantle layer
 Form motor areas of sp.cord-
Anterior horn
 Their nerve fibres pass through
the marginal layer and emerge as
ventral roots of spinal nerve

5.  Form dorsal sensory areas of
spinal cord
 Nerve fibres penetrate marginal
zone and ascend or descend for
several levels to form Association
neurons

6.  Between alar and basal plates

7.  Present in midline region
 Contain no neuroblasts
 Serve as pathways for nerve
fibres from one side to the other

8.  Glioblasts are formed from
neuroepithelial cells after the
form.of neuroblasts has ceased
 Supporting cells
 Pass through all layers of spinal
cord
 IN MANTLE LAYER:
 Differentiate to form Protoplasmic
astrocytes & Fibrillar
astrocytes(Nerve regeneration)
 IN MARGINAL LAYER:
 Differentiate to form
oligodendrocytes (Myelinate
ascending&descending fibres in CNS
while schwann cells are responsible
for myelination in PNS)

9.  Phagocytes
 Formed in 2nd half of
development from mesenchyme
 Form ependymal cell layer after
neuroblasts and glioblasts
formation is over

10.  Present in T1-L3 segments of
spinal cord