CNS Dev't Flashcards
neurulation occurs until
Day 28
entire process of neural fold formation, elevation, and closure
neurulation
appearance of notocord and precordial mesoderm induces overlying ectoderm to thicken forming
neural plate
How is neural fold formed
lateral edges of the neural plate begins to elevate
depressed region in the midline of neural plate
Neural grove
neural folds fused midline
neural tube
neural tube opens posteriorly and anteriorly called
neuropores
closes by day 25
anterior (cranial) neuropore
closes by day 28
posterior (caudal) neuropore
Complete neurulation
closure of posterior neuropore
CNS with T-shaped form is having an
Elongated caudal end
Broader cranial end
3 vesical stage
Prosencephalon
Mesencephalon
Rhombencephalon
Flexures present during 27 days
Cephalic
Cervical
5 Vesical stage
prosencephalon : Telencephalon (lateral ventricle, cerebral hemisphere) & Diencephalon (3rd ventricle and thalamus, hypothalamus)
Mesencephalon: Aqueduct of Sylvius (tectum, crus cerebri)
Rhombencephalon :Metenceohalon ( upper 4th vent, pons& cerebellum) Mesencephalon (lower 4th vent, medulla)
separates Mesencephalon and Rhombencephalon
Rhombocephalic isthmus
Junction of the hindbrain and SC ; disappears at 4th month
Cervical Flexure
Flexure at midbrain region; disappears at 3 vesical stage
Cephalic flexure
between Metencephalon and Myelencephalon
Pontine Flexure
Cavity of cerebral hemispheres
lateral ventricles
Communicates the lateral ventricle with 3rd ventricle
Interventricular foramina of. monroe
cavity of diencephalon
third ventricles
lumen of mesencephalon ;connects 3rd and 4th ventricles
aqueduct of sylvius
Cavity of rhombencephalon
4th ventricle
lumen of Sc
central canal
collection of neuroepithelial cells which extends the entire wall and forms
Pseudostratified epithelium
further differentiation of neuroblasts and makes up the grey matter of SC having a large round nucleus and pale nucleoplasm
Mantle layer
continous addition of neuroblasts to mantle layer results to
Ventral and Dorsal thickening
Sensory area formed from dorsal thickening of the neural tube
Alar plate
motor area formed by ventral thickening
Basal plate
boundary of basal and alar plates
Sulcus Limitans
midline of neural tube serves as pathway for nerve fibers
Roof and Floor plates
small group of neurons accumulating between sensory and motor plates
intermediate horn
outermost layer of SC that comproses the white matter and is myelinated
Marginal layer
has transient dendrites that are lost when entering mantle later
neuroblast/ primitive nerve cells
temporary round cell
Apolar neuroblast
2 cytoplasmic processes on opposite cite of cell body
Bipolar neuroblasts
Has primitive axon and primitive dendrites
multiplar neuroblasts
axons in the basal plate penetrate the marginal layer and become visible on ventral aspect of cord
ventral motor root of spinal nerve
axons in alar plate penetrate marginal layers and ascend or descend as
association neuron
formed when neuroblast production ceases and migrate fr neuroepithelial layer to mantle and marginal
Glial blast
glialblast in mantle and is seen b/w blood vessels
protoplasmic astrocytes and fibrillar astrocytes
glialblast migrated to marginal layers and forms myelin sheath
Ologodendrial cells
from vascular mesenchyme and is highly phagocytic
microglial cells
when neuroepithelial cells ceases to produce neuroblasts, seen in central canal of SC
ependymal cells
from cells that dissociate from the lateral border of the elevated fused neural fold during the elevation of neural plate and gives rise to sensory ganglia
neural crest cells
penetrate dorsal portion of the neural tube in the dorsal horn ans ascend to marginal layers
Centrally growing ( dorsal sensory root)
joins fibers of ventral motor roots to form trunk of spunal nerve
peripherally growing processes
present during 4th mo of fetal life and myelinate perioheral nerves forming neurolemma or neural sheath derived from neural crest cells
schwann cells
myelinate fibers in SC derived from glialblasts
Oligodendrial cells
Changes in the 3rd month of devt
SC extend entire length of embryo
Spinal nerves emerging fr respective intervertebral foramina at level of origin
terminal end of the cord during birth
L2-L3
terminal end of the cord during adult
L1-L2
threadlike extension of Pia matter at end of SC; marks the regression of SC and supports the cord
filum terminale
covered with dura extending from S2 to coccyx
coccygeal ligament
nerve fibers below end of cord
cauda equina
gives rise to medulla oblongata
Myelencephalon
includes CN12 supplying tongue
Median somatic efferent of Basal plate of myelencephalon
includes the CN 6,9,10 supplying striated m of pharyngeal arches
Intermediate special visceral efferent
include the involuntary ms of respiratory tract, GIT and ❤️
lateral general visceral efferent of basal nuclei of myelencephalon
recieves interoceptive info from GIT and ❤️
medial general visceral afferent of alar plate of mylencephalon
recieves impulses fr taste buds, oropharynx, epiglottis, Cn8 for hearing and balance
intermediate special viscreal afferent of alar plate of myelencephalon
recieves pain touch and sensory from pharynx and CN9
lat somatic visceral afferent of alar plate of myelencephalon
vascular mesenchyme covering roof plate
pia matter
pia matter + roof plate
tela choroidea
tuft like invaginations that produce CSF
choroid plexus
forms the cerebellum (pathway for posture) and pons (pathway for nerve fibers)
Metencephalon
gives rise to nucleus of CN6
medial somatic afferent of basal plate of metencephalon
contain nuclei of CN5&7
Intermediate special visceral efferent of basal plate of metencephalon
supply submandibular and sublingual glands
lateral general visceral efferent of basal plate of metencephalon
dorsolateral part of alar plates bending medially
Rhombic lips
formed when potine flexure deepens and rhomben lips are compressed at 12th wk of devt
cerebellar plate
cerebellar plate contains:
Vermis ( small midline portion below ant and post colliculi) Cerebellar Hemisphere (two lateral portions alongside vermis) Flocculonodular lobe (primitive part of cerebellum)
midbrain
mesencephalon
represented by CN3&4 innervationg eye muscles
Medial somatic efferent of basal plate of mesencephalon
bby nucleus of Edinger-Westphal innervating sphincter pupillary muscle
General Visceral efferent of basal plate of mesencephalon
pathway for nerve fibers from cerebral cortex to lower center in pons and SC
Crus cerebri
part of alar plate of mesencephalon that fxn as correlatuon and reflex center for visual impulses
ant (sup) colliculus
synaptic relay for auditory reflexes
post(inferior) colliculi
develop fr median portion of prosencephalon and 1 roof plate and 2 alar plate and no floor or basal plate
Diencephalon
most caudal part of roof plate appearing as ep thickening which channels through light and dark affect behavioral rhythms
Pineal body or epiphysis
dorsal region of alar plate
thalamus
fusion of right and left thalamic regions
massa intermedia or interthalamic connexus
ventral region of alar plate which diff into nuclear areas that regulates visceral fxns including sleep
hypotahlamus
distinct protuberance on ventral surface of hypothalamus
mamillary body
from ectodermal outpcketing and floor of dienceohalon
piyuitary gland
most rostral or anterior of brain vescicles
Telencephalon
consist of 2 lat cerebral hemispheres and median lamina
telencephalon
lateral ventricles communiacte with lumen of diencephalon via
interventricular foramina of Monro
arise at the beggining of 5thweek of devt
cerebral hemispheres
repidly growing region with striations
corpus striatum
two divisions of corpus striatum
Lentiform nucleus (ventrolateral portion) Caudate nucleus (dorsolateral portion)
forms at roof of hemisphere but protrudes to lateral ventricle
Choroid plexus
above the choroidal fissure bulges into kateral ventricles and fxns in olfaction
Hippocampus
Cerebral hemispheres grow into:
Anterior (frontal lobe)
Dorsal (temporal lobe)
Inferior(occipital lobe)
depressed area b/w frontal and temporal lobe
Insular lobes
originates from pallium
Cerebral cortex
regions of cerebral cortex
palleopalium (immediately lateral to corpus striatum)
neopallium(in b/w palleopaliumun and hippocampus)
fiber bundles lining midline connecting L and R halves of hemisphere
commisure
appears on 19th week and connects non olfactory area of R and L cerebral cortices
Corpus Callosum
results to continous expansion of neopallium
corpus callosum
fibers connecting olfactory bulb and related brain areas to one hemisphere of opposite side
anterion commisure
arise in hippocampus converging to lamina terminalis
hippocampal or fornix comissiure
below the stalk of pineal gland
habenular commisure
aooear on rostral wall of diencephalom
optic chiasm
incomplete development of ventral arches
spina Bifida
what prevents spina bifida
folic acid
defectin vertebral arches still covered by skin and does not involve underlying neural tissue
Spina bifida occulta
Severe NTD defect in neural tissues
Spina bifida cystica
NT defect in which only fluid filled meninges bulge through; affected occipital bone is smal
meningoceole
another ossification defect wherein meninges and part of the brain are herniated throughout the skull
meningomyelocoele
failure of the neural tube to close the remaining as flattened mass or neural tissue. exposes neural tissues making it susceptible to infection
rachishisis
spectrum of abnormalities due to loss of midline structures resulting to malformations of brain and face ; frontal loves and basal ganglia fused
Holoprosencephaly
large clefts extending from cortex to ventricle sometimes causing loss of brain tissue; mutation in homeobox EMX2
Schizencephaly ( open or closed )
NTD characterized by sac like protussions of brain and membranes covering it. Caused by failure of neural tube to close. classified to meningocoele, encephalocoele, naso orbital, naso ethmoidal, and overlapping of such
encephalocoele