University:
Western Sydney University
Course:
MEDI 2003 | Clinical Sciences 2
Academic year:

2024
Views:

288

Pages:

2
Author:

Mariam A.

Spinal Cord Embryology      The wall of a recently closed neural tube consists of neuroepithelial (NE) cells that extend the entire thickness of the wall and form a thick pseudostratified epithelium. Immediately after closure of the tube, NE cells divide rapidly, producing even more NE cells, collectively creating the neuroepithelial layer (neuroepithelium). After closure, NE cells begin to give rise to another cell type, neuroblasts, which are primitive nerve cells that are characterised by a large round nucleus with pale nucleoplasm and dark-staining nucleolus. Grey matter and white matter both come from neuroblasts. o Neuroblasts form the mantle layer, a zone around the neuroepithelium, giving rise to the grey matter of the spinal cord. o The outermost layer of the spinal cord, the marginal layer, contains nerve fibres emerging from the neuroblasts from the mantle layer. Since there is myelination of these nerve fibres, it gives off a white appearance, forming the white matter of the spinal cord. As a result of continuous addition of neuroblasts to the mantle layer, each side of the neural tube shows a ventral and a dorsal thickening. o Ventral thickening, the basal plates, contains the ventral motor horn cells that form the motor areas of the spinal cord. o Dorsal thickening, the alar plates, contains the dorsal sensory horn cells that form the sensory areas. o Longitudinal groove, the sulcus limitans, marks the boundary between the two. o The ventral and dorsal midline portions, the floor and roof respectively, do not contain neuroblasts and serve primarily for nerve fibres crossing from one side to the other. o A group of neurons accumulate between the two horns to form the intermediate horn. Neurons here have sympathetic activity at T1 – L3.