Development of Brain and Spinal Cord Flashcards
What is the last system to develop
CNS
When does Myelination of the Brain begins
Third trimester , week 28 to 40
Brain development in the prenatal months are under which type of control
Genetic and environmental control
What are the primary Vesicles that arise from the neural tube at the cranial end
1- Prosencephalon
2- Mesencephalon
3- Rhombencephalon
The Prosencephalon forms what ( secondary vesicles )
1- Telencephalon
2- Diencephalon
The mesencephalon forms what ( secondary vesicles )
Stays the same , mesencephalon
The Rhombencephalon form what ( secondary vesicles )
1- Mesencephalon
2- Myelencephalon
What are the structures of the Telencephalon
Cerebrum : cerebral hemispheres, cortex , white and grey matter
What are the structures of the Diencephalon
Thalamus , Hypothalamus , epithalamus , retina
What are the structures of the Mesencephalon
Brainstem : midbrain
What are the structures of the Metencephalon
Brain stem : pons and Cerebellum
What are the structures of the Myelencephalon
Brain stem : medulla oblongata
By the 4th week the neural tube bends to produce what
1- Midbrain flexure ( ventrally ) between the prosencephalon and mesencephalon
2- Cervical flexure between hind brain and the spinal cord
3- Pontine flexure in the hindbrain
What is the purpose of the brain flexures
So the brain can fit into the cranial cavity ( bends it )
When does the pontine structure usually happen
5th week
Explain the development of the ventricles
1- Dervied from dilation of the neural canal of the neural tube
2- Dilations in the prosencephalon lead to formation of lateral ventricles and third ventricle
3- Cavitation of the mesencephalon forms the cerebral aqueduct
4- Rhombencephalon dilation leads to formation of Fourth ventricle
Where do the meninges arise from
Dura : mesoderm surrounding neural tube
Pia & arachnoid : neural crest cells
Explain how the neural tube forms the neurones
cells in the wall of the neural tube ( ependymal ) give rise to neurones.
Divides into
1- Mantle layer : intermediate layer containing cell bodies of motor neuron ( grey matter)
2- Marginal layer : contains axons of motor neurons ( white matter )
What are the divisions of the Mantle Layer
1- Alar Plate : dorsal sensory cell bodies receiving sensory axons form DRG
2- Basilar plate : ventral , cell bodies for motor neurones
3- Neuroepithelium gives rise to neuroblasts and glioblasts
Cell bodies in Alar plate develop into
Dorsal gray columns , dorsal root of spinal nerves
Cell bodies in Basal plate develop into
Ventral grey Columns, ventral root of spinal nerves
Cell Bodie sin the roof plate develop into
Posterior median septum
Cell bodies in the floor plate develop into
Ventral medial fissure
Explain Neurogenesis proliferation
Process of neurones and glia proliferating , migrate and are specified to form mature brain
Proliferation :
1- Neuroepithelial cells lining neural tube differentiate into neuroblasts and glioblasts
2- Glioblasts form Oligodendrocytes and astrocytes
3- Neuroblasts form Neurones
4- Then after ependyma cells form the epithelium of the choroid plexus
Explain Neurogenesis Migration
2 directions of migrations
1- Radial migration ( straight )
- Most cortical neurones migrate this way
- Occupy the deepest cortical layers , formed first
2- Tangental migration ( at angle )
2 different mechanisms of migration
1- somal translocation is self directed : nucleus of cell moves though cytoplasm and shortens axon
2- Glial mediated migration relies on radial glial cells
- Neurone wraps around glial cell and migrates along it
Explain Neurogenesis Synpatogenesis
1- After elongation axons and dendrites make contacts and establish initial synapses
2- Synapses are constantly reconfigured in development and life
3- synaptic density in cortex in 1 to 2 years of age is at the highest , then stabilizes in adulthood
