Embryology and abnormalities

Question 1

what induces the ectoderm to form neural plate and tube

Answer 1

notochord

Question 2

what are the three germ layers

Answer 2

ectoderm, mesoderm, endoderm

Question 3

primary neurulation, secondary neurulation

Answer 3

1-neural plate>folds and groove>tube. 2- forms spinal segments below S2.

Question 4

types of spina bifida in increasing order of severity

Answer 4

oculta, lipoma and lipocele, cystica (meningocele, meningomyelocele), rachischisis

Question 5

what defects do you see with meningomyelocele

Answer 5

sensory and motor in bowel, bladder, lower limb

Question 6

tethered cord syndrome: problem with 1* or 2* neurulation? what happens? Results in?

Answer 6

Seconday. fibrous bands pull down on cord. Arnold-Chiari and hydrocephalus

Question 7

Types of exencephaly

Answer 7

encephalocele (w/ or w/o brain tissue). Anencephaly (most common cause of stillbirths)

Question 8

Name the primary brain vesicles

Answer 8

prosencephalon (forebrain), mesencephalon (midbrain), rhombencephalon (hindbrain)

Question 9

name secondary brain vesicles and what comes from them

Answer 9

telencephalon (cereb hemis), diencephalon (thal,hypothal), mesencephalon (midbrain), metencephalon (pons, cerebellum), myelencephalon (medulla)

Question 10

folding of the midbrain in the ventral direction. consequences

Answer 10

cephalic flexure. vertical orientation of cord and brianstem, horizontal orientation of forebrain

Question 11

two defects in ventral induction

Answer 11

holoprosencephaly, agenesis of the corpus callosum

Question 12

three layers of neural tube

Answer 12

neuroepithelial layer (all cells of cns except microglia), mantle layer (gray matter), marginal layer (white matter)

Question 13

two parts of mantle layer and what divides them

Answer 13

basal (somotomotor [ant] and visceromotor [lateral]) and alar plates (sensory [post]). Sulcus limitans

Question 14

what do the roof and floor plates of enural tube form?

Answer 14

commissures where axons cross from one side to the other

Question 15

when does myelination occur

Answer 15

4th gestational month to end of second year

Question 16

in ventricles: what happens to basal and alar plates? roof plate?

Answer 16

form medial motor and lateral sensory areas divided by sulcus limitans. Roof plate gets covered by pia to form tela choroidea which invaginates to form choroid plexus

Question 17

four steps necessary to form cerebral hemispheres

Answer 17

proliferation, migration, organization, myelination

Question 18

describe proliferation and migration and organization stages

Answer 18

neuroblasts and glioblasts. Neurblasts migrate along radial glia, pass cells of earlier birth, form 6 layers of cortex

Question 19

defects in proliferation phase

Answer 19

microcephaly, macrocephaly, tuberous sclerosis, focal cortical dysplasia

Question 20

defects in neuronal migration

Answer 20

seizures (abnormal conduction), lissencephaly, schizencephaly, focal dysgenesis, heterotopias

Question 21

when does neurulation begin

Answer 21

day 17

Question 22

what affects 2/3 of all NTDs

Answer 22

folate metabolism. All women of child bearing age should take it

Question 23

Relationship of radial glial cells and neurons in cortex

Answer 23

same stem cells gives rise to glial then neurons. Radial cells move from ventricular zone to SVZ then back and forth escorting new cells

Question 24

diastomyelia

Answer 24

notochord is split by adhesion b/w endo and ectoderm

Question 25

what genes are mutated in classical lissencephaly. What do they affect

Answer 25

LIS1, DCX. Microtubule formation

Question 26

subcortical band herterotopia: what? what mutation? what gradient?

Answer 26

bands of grey matter b/w cortex and lat. ventricles. DCX mutation (A>P gradient)

Question 27

males with dcx get___. females get___. What inheritance? what protein does it produce

Answer 27

lissencephaly, subcortical band heterotopia. X-linked! Doublecortin

Question 28

problems of organization phase

Answer 28

polymicrogyria. Predilection for perisylvian areas.

Question 29

implication of malformation of cortical development (MCD)

Answer 29

epilepsy, learning disability, cerebral palsy, developmental delay

Question 30

Three ways primary neurulation can go awry

Answer 30

diastomyelia, premature disjunction of neural tube from ectoderm (lipomas), nondisjunction (myelomeningocele)