Development Of Spinal Cord Flashcards
Development
- It develops from neural tube caudal part
- Neural tube is formed of one layer of columnar epithelium surrounding central canal then this layer proliferates and neural tube becomes formed of:
- Two lateral thick walls
- Thin roof and floor plates
Lateral wall differentiates into 3 layers
- Inner ependymal layer
- Middle mantle layer
- Outer marginal layer
Inner ependymal layer
Gives rise to:
1. Ependymal cells lining spinal cord
2. Neuroblast cells which migrate to middle (mantle) layer
Middle mantle layer
Formed of neuroblasts (nerve cells) which form grey matter
Outer marginal layer
Contains nerve fibers emerging from neuroblasts and form white matter
Grove (sulcus limitans) appears on lateral wall inner surface on either sides dividing into:
- Alar plate
- Basal plate
Alar plate
Contains sensory cells and forms spinal cord posterior horn
Basal plate
Contains motor cells and forms spinal cord anterior horn
Spinal cord growth
Spinal cord growth rate is slower than vertebral canal:
1. In 3rd uterine month: it occupies the whole vertebral canal length
2. At birth time: spinal cord lower end lies at L3 lower border
3. In adult: spinal cord lower ends lies at L1 lower border
Canal lumen becomes narrow
Myelination of spinal cord fibers
Begins in 4th month intrauterine life is completed by 1st year end
Congenital anomalies
- Spina bifida occulta
- Meningocele
- Meningomyelocele
- Rachischisis
Spina bifida occulta
Failure of fusion of dorsal parts of one vertebra
Meningocele
Meninges bulge through defect
Meningomyelocele
Meninges and spinal cord bulge through defect
Rachischisis
Failure of neural tube closure
