Embryology of the Nervous system part 1 Flashcards
What is the first indication of nervous system development?
Neural plate and neural groove formation in the 3rd week.
What does the neural tube differentiate into?
Central nervous system
What do neural crests cells form?
Forms most of the PNS and ANS
Cranial 2/3 of the neural tube represents________________
Future brain
Caudal 1/3 of the neural tube represents_________________
future spinal cord
What type of cells are found in the wall of the neural tube?
Pseudostratified columnar neuroepithelium
How does the central canal of the spinal cord form? Specify the weeks as well
Lateral walls of neural tube thicken, reducing size of
neural canal – until only a central canal of spinal cord
exists at ~ 9-10 weeks
what develops from the neural tube caudal to the 4th somite?
SC
What signalling substance is important during spinal cord development?
Retinoic acid signalling is essential in development of spinal cord from early patterning to neurogenesis
Describe the marginal zone and what it forms
Marginal zone, containing outer part of neuroepithelial
cells forms
Eventually becomes white matter of the spinal cord
as axons grow into it from surrounding nerve cell
bodies, spinal ganglia and brain
How do neuroblasts develop into neurons?
Neuroblasts become neurons as they develop cytoplasmic
processes
What does neuroepithelium of the neural tube form? (2)
Ventricular zone (ependymal layer)
Gives rise to all neurons and macroglial cells
(macroglia- e.g. oligodendrocytes and astrocytes) in spinal cord
When does glioblast formation start?
It starts when the neuroblast formation ceases. Then neuroepithelium will form glioblasts which will migrate to the intermediate and peripheral zone.
How is the intermediate zone formed?
Dividing neuroepithelial cells in ventricular zone differentiate into primordial neurons – neuroblasts
Form an intermediate zone (mantle layer)
What do glioblasts form?
Astroblasts form astrocytes
Oligodendroblasts form oligodendrocytes
What is the order in which epedymal cells, neuroblasts and glioblasts form?
Neuroblasts are formed first and goes to the marginal zone, Glioblasts are formed second and goes to the I.M and Marginal zone
Ependymal cells form last and stick around in the ventricular zone
Describe microglia
Scattered in white and gray matter of spinal cord
* Small cells, derived from mesenchyme
Where do microglia originate? When do they invade the CNS?
Invade CNS in late foetal period, after being penetrated by
blood vessels.
* Originate in bone marrow, part of mononuclear
phagocytotic cell population
What is the sulcus limitans?
Sulcus limitans – shallow, longitudinal groove, produced on each side
Separates alar plate and basal plate, plates produce longitudinal bulges
Differentiate between alar plates and basal plates
Alar plates are afferent, they form dorsally
Basal plates are efferent, form anterolaterally.
What do alar plates form? Explain
Cell bodies form dorsal gray columns and extend length of
spinal cord
In transverse sections these columns appear as dorsal gray horns
Neurons in columns form afferent nuclei
As the dorsal plates enlarge, they form________________________
Dorsal median septum
What do basal plates form? Explain
cell bodies form ventral and lateral gray columns and extend length of spinal cord
Appear as ventral and lateral gray horns in transverse sections
Axons of ventral horn cells grow out of spinal cord
Forms ventral root of spinal nerves
Basal plates bulge ventrally on each side of the median plane, and this forms_____________ AND ______________
Ventral median septum
Ventral median fissure
