SDL: Neuroembryology Flashcards
what does the midline axial mesoderm form from?
the notochord
what does the notochord induce?
the overlying ectoderm, to form the neural plate
what is the difference between primary and secondary neurulation?
primary: developing notochord induces the overlying embryonic ectoderm to thicken and form the neural plate– secondary: coalescence of caudal mass mesenchymal cells into a rod followed by cavitation to form a tube and fusion with primary neural tube
in which process (primary or secondary neurulation) does the notochord play a role?
primary neurulation: notochord induces the overlying embryonic ectoderm to thicken and form the neural plate
what embryonic germ cell layer forms from the neural tube in primary and secondary neurulation?
primary: ectoderm fusion; secondary: mesenchymal condensation, epithelial translocation
what structures related to the PNS do neural crest cells give rise to?
spinal nerve ganglia, cranial nerve ganglia, ANS ganglia, schwann cells
what is the specific timing difference between closure of the anterior and posterior neuropores? which occurs last?
anterior neuropore closes on day 25; posterior neuropore closes on day 27
the 2 types of spina bifida
closed skin (occulta), open skin condition (neural plate is directly exposed to amniotic fluid)
spina bifida occulta typically occurs where? this is an example of what type of neurulation defect?
lumbar/upper sacral junction; secondary neurulation defect
if spina bifida occulta occurs in the upper regions of the vertebral column, it would arise from incomplete fusion of post. neuropore during..
primary neurulation (this is rare)
what is the difference between spina bifida occulta versus a meningocele versus a myelomeningocele? which would cause more severe neurological symptoms?
occulta: defect in vertebral arches, doesn’t involve neural tissue (no symptoms); meningocele: fluid-filled sac of meninges pokes through defect (Neuro symptoms); myelomeningocele: neural tissue in the fluid sac (neuro symptoms)
5 neural tube defects that are examples of primary neurulation defects
craniorachischisis totalis, anencephaly, myeloscisis, encephalocele and myelomeningocele
what would you call a defect where primary neurulation failed to occur anywhere in the fetus?
craniorachischisis totalis?
what would you call a defect where the ant neuropore failed to close in the region overlying the top of the head? what happens to the neural plate that is located in this region?
anencephaly; exposed neural tissue dies
what would you call a defect where there is an outpocketing of neural tissue in an instance where there is a partial failure of closure of the anterior neuropore in the region of the back of the head?
encephalocele
what would you call a defect in which there is complete failure to close the post neuropore?
myeloschisis
what risk factors are there for neural tube defects? how can a pregnant mother reduce the risk of having a baby with a neural tube defect?
folic acid deficiency (sexually active women should take folic acid 2 mos before conception and throughout pregnancy), diabetic mothers, alcoholics, nutritional deficiencies
which protein would increase in maternal serum and amniotic fluid in cases of neural tube defect?
alpha-fetal protein
when should women of childbearing age begin taking daily supplements of folic acid? why?
2 mos before conception and throughout pregnancy to prevent neural tube defects
what are the molecular mechanisms of neurulation? (will only be tested on sonic, bone morogenic protein, homeobox genes)
notochord secretes hedgehog protein that induces overlying ectoderm to differentiate into neuroectoderm; opposing sonic hedgehog bone morphogenic protein gradients promote the dorsoventral differentiation; spatial and temporal differences in the homeobox genes are important for anterior-posterior axis development and secondary neurulation
which cells give rise to neuroblasts in the developing spinal cord?
neural crest cells in the cerebral cortex
which cells give rise to the astrocytes and oligodendroglia?
neuroepithelial cells
what causes holoprosencephaly?
failure to form the two cerebral hemispheres- fails to cleave, remains fused as a single midline entityra
what is the function of the radial glia in the developing cerebral cortex?
neurons migrate along them; also progenitor cells
what is the difference between schizencephaly, lissencephaly, pachygyri or polygyri?
schizencephaly (cleft brain, paralysis, seizures); lissencephaly (smooth brain, few gyri); pachygyri (broad gyri, too few gyri); polygyri (small gyri)
what is the underlying cause of schizencephaly, lissencephaly, pachygyri or polygyri?
disorders of migration
which condition has an abnormal cleft in the brain?
schizencephaly
which condition has a generalized absence of cerebral cortical gyri?
lissencephaly
