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development of CNS


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When does the neural ectoderm form the neural plate?
In the early embryo (~18 days)
When does the neural tube become internal
~4 weeks
From whence the the ventricular system and central canal of the spinal cord
The cavity of the neural tube
What are the four concentric zones of the neural tube
the ventricular & subventricular, mantle, and marginal zones or layers
from whence the neurons
neuroblasts in the ventricular zone of the neural tube
from whence ependymal cells
spongioblasts of the ventricular zone of the neural tube
from whence macroglia
glioblasts of the ventricular zone of the neural tube
when is the most rapid phase of neuronal mitotic activity
from 12-20 wks of gestation, the first critical period of brain development
From whence the mantle layer
from migrating primitive neurons generated in the ventricular zones
The marginal layer becomese
the white matter of the mature CNS
Areas where neural tube has not fused by 4 weeks
anterior neuropore, rhomboid fossa, posterior neuropore
rhomboid fossa becomes what
the 4th ventricle of the mature brain
what are the three vesicles or dilations or the developing brain
the prosencephalon (forebrain), the mesencephalon (midbrain), and the rhombencephalon (hindbrain)
Prosencephalon becomes
telencephalon and diencephalons
when is the second critical period of brain development?
third trimester of gestation through about 2 yrs. of age
first part of commissural system in development
lamina terminalis
embryonic Mesencephalon becomes:
Rhombencephalon becomes:
metencephalon and myelencephalon
Rhomboid fossa Ventricular zone becomes:
cerebellar plate (analogous to the cortical plate)
mantle layer of the cerebellar plate will differentiate into
neurons of deep cerebellar nuclei, Purkinje cells, and Golgi cells
Cells located at the rhombic lip; a small group of specialized somatic sensory neurons (General Somatic Afferents; GSA) which give rise to an external granular layer which develops on the outside of the cerebellar cortex with cells which will differentia
granule, basket, and stellate cells in the mature cerebellum; granule cells will migrate so that in the adult brain they come to occupy the deepest layer of the cerebellar cortex (the granule cell layer);
Neurons generated from the rhombic lip are also thought to migrate into the brainstem to become⬦
the pontine nuclei and the inferior olive
Medulloblastomas definintion
malignant embryonal tumors of the cerebellum with a tendency to metastasize; constitute ~20% of pediatric CNS neoplasms with a peak incidence at 3-8 yrs; occur with greater frequency in males
from whence the choroids plexus
At two areas of the developing nervous system where the neural tube does not fuse, the pia (the innermost meningeal layer) and ependymal cells interact; Lateral ventricle; the major site of CSF production in the CNS, & 4th ventricle
define Encephalocele (“pouch”)
failure of fusion above the spinal cord, most commonly the dorsal and occipital area; no bone forms and a pouch of brain tissue extrudes from the skull
the two cerebral hemispheres form, but then a regression of the tissue occurs, and the cavity fills with CSF; can be due to maternal trauma, or to vascular problems in the fetal brain
failure of the normal migration of neurons in the telencephalon to form the normal C-shaped configuration of the hemispheres
in humans neural plate formation begins when?
day 18
deep neural groove has formed by what day
neural tube closure begins at what day, begins where in tube
day 20/21, starts in middle of tube
cranial neuropore closes what day
caudal neuropore closes what day

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