Development of the CNS Flashcards
Most common type of cancer in infants/children
Neuroblastoma
-Develops from neural crest cells
Week by which the neural tube has fused
4
Ventricular zone
Contains cells with mitotic activity that generate neuroblasts, glioblasts, and neuroglia
First critical period (brain development)
12-20 weeks of gestation
200,000n neurons/min generated, however, >50% will be lost later
Mantle layer
Forms from migrating primitive neurons in the ventricular zone
-Will become gray matter
Marginal Layer
Will become the white matter of the CNS containing axons
3 areas where neural tube has NOT fused by week 4
- Anterior neuropore- Cerebral hemispheres develop here
- Rhomboid fossa- Cerebella will develop over this
- Posterior Neuropore- Closes off after 4 weeks
Prosencephalon
Gives rise to the Telencephalon and Diencephalon
- Will also form the neural retina and optic nerve
- Neurons that migrate=> coritcal plate (cerebral cortex)
Neurons that don’t=> deep nuclei (diencephalon)
Mesencephalon
Gives rise to the mesencephalon
Rhombencephalon
Gives rise to the metenceophalon (pons, cerebellum) and myelencephalon (medulla)
Second Critical Period (brain development)
Third trimester-2 years
Extensive dendritic arborization, axon growth, and synaptogenesis
Lamina terminalis
Thin, membranous structure located dorsal to optic chiasm; forms the anterior wall of the 3rd ventricle which becomes the corpus callosum of the mature brain
Aqueduct of Sylvius
Connects the 3rd to 4th ventricles; remnant of the primitive cavity of the neural tube
4th ventricle of brain
Formed when cerebellum closes over the rhomboid fossa
Choroid Plexus formation
The pia and ependyma (cells that line the neural tube and ventricles) interact at the anterior neuropore and rhomboid fossa to form the choroid plexus
Anencephaly
Failure of the anterior neuropore to close
-Forebrain fails to develop; incompatible with life
Encephalocele
CNS and meninges protrude thru defect in skull formation
-Occurs most common occipitally; can be repaired if less severe
Spina bifida
Failure of the caudal neural tube to close
- …occulta- not severe; loss of vertebra
- Myelomeningocele- Most severe; contains nerves
Holoprosencephaly
Failure of prosencephalon to separate into two hemispheres; severe facial abnormalities
*Occurs after 4wks of development
Lissencephaly
“agyria”
smooth-brained
Associated w/ agenesis of the the corpus callosum
Heterotopia
Pocket of normal neurons that have formed in the wrong place
Fetal stroke
CNS blood supply cut off
*Major cause=maternal cocaine use
Encephaloclastic defects
Loss of brain tissue during development
*Commonly caused by hypoxic-ischemic damage
Porencephaly
(Schizencephaly)
Abnormal opening in the ventricular system resulting in the loss of brain tissue
Hydranencephaly
Necrosed brain tissue in forebrain gets replaced with fluid enclosed by a thin membrane
-Not compatible w/ life
Choroid plexus in the 3rd ventricle
Occurs when the lateral ventricles extrude thru the foramen of Monro
Neural Tube Defects
Occur due to a failure of neural tube closure or from axial mesodermal defects
*Occur before week 4
Choroid plexus found in the 3rd ventricle
Occur when the lateral ventricles protrude thru the foramen of Monro during development
Give rise to mature ependymal cells
Glioblasts
Diverticulation of the neural tube
Gives rise to the three primitive vesicles
-Occurs at the most rostral end
