Nervous system embryology and Congenital malformations

Question 1

What is gastrulation?

Answer 1

from bilaminar disc to trilaminar disc (cells drop down from primitive streak - produced by epiblast cells)

Question 2

What does the ectoderm form?

Answer 2

epidermis and nervous system

Question 3

What does the neural tube form from?

Answer 3

Neural plate (thickening of ectoderm), forms Neural folds which then form neural plate

Question 4

What are the neuropores?

Answer 4

They are the ends of teh neural tube (anterior and posterior), last sections to close, to allow for slightly more development at the ends.

Question 5

When do eht neuropores close?

Answer 5

Starts closing at day 18, ends aorund day 27 (week 3-4)

Question 6

Neuro tube defect examples?

Answer 6

Anencephaly
Enencehalocoele
Spina Bifida

Question 7

WHeat is Exencephlaly/Anencephaly(Meroencephaly)

Answer 7

When the anterior end doesn’t fully close on time and so the brain cells then get in contact with the amniotic cavity and degrade. Incompatible with life.

Question 8

What is Encephalocoele?

Answer 8

The brian is fully there, but some is poking out of the skull because the anterior end wasn’t quite fully closed and so the skull forms around the the section that isn’t fully closed.

Question 9

Spina Bifida :
a)Spina Bfida Occulta?
b) Spina Bifida Cystica: Meningocele/meningomyelocle?myeloschisis

Answer 9

Caudal end not quite closing so again the bone doesn’t form around some of it and so some spinal chord etc sticks out. Can cause defects below level of spinal chord depneding on where it is at and severity:

a)Spina Bfida Occulta? Very minor - O so not really sticking out, often no clinical signs maybe hair tufts or dimple.
b) Spina Bifida Cystica:
Meningocele - meninges and spinal fluid protrusion. Least severe
meningomyelocle- Protrusion inc. Nerve roots/spinal chord. Neuro defects. linked with hydrocephalus
myeloschisis - SChize - worst, spinal chord in bulding area as neurofolds didnt fuse

Question 10

How can we decrease the risk of the risk of neural tube disorder?

Answer 10

Folic acid in child bearing mothers

Question 11

Rsk factors for neural tube defects?

Answer 11

Genetic
Nutritional (low folate/high vit A)
Environmental (Hyperthermia/drugs eg sodium valproate)

Question 12

High levels of alpha-fetoprotein in serum can be an indication of what birth defect for the embryo?

Answer 12

Neruaol tube defect eg spina bifida

Question 13

What are hte 3 primary brian vesicles and when do they develop?

Answer 13

Forebrain (Prosencephalon), midbrain (Mesencephalon) and hindbrian (Rhombencephalon)
Develop at week 4

Question 14

What are the 5 seconday brain vesicles and when do they appear?

Answer 14

forebrain forms bothe the telecephalon and Diencephalon

Midbrain still there (mesencephalon)

Rhombencephalon forms the metencephalon and the Myelencephalon

Question 15

What are the 3 flexure of our cns and when do thye occur?

Answer 15

Cephalic flexure (between hind and mid brain) end of 3rd week
Cervical flexure (Between the hind brain and spinal chord (end of 4th week)
Pontine flexure (in hind brain) end of 5th week

Question 16

What forms from the forebrain?

Answer 16

Diencephalon (thalamus, hypothalamus and the pituitary)
Telencephalon (Cerebral hemispheres, hippocampus and basal ganglia)

Question 17

What forms from Midbrain?

Answer 17

The midbrain. Inc. Superior and inferior colliculi)

Question 18

WHat forms from the hind brian?

Answer 18

meterncephalon (cerebellum and pons)
Myelencephalon (medulla)

Question 19

What is Lissencephlay?

Answer 19

“Smooth brian”: Sulci and gyri don’t form. Slow development and often die around age 10

Question 20

What is polymcrogyraie?

Answer 20

Too many sulci and gyri. Form neurological problems eg siezures

Question 21

What do the ventricles form from (in the neural tube ):
Lateral ventricles
3rd ventricle
Mesencephalon
Metencephalon
Myelencephalon
Spinal chord

Answer 21

Lateral ventricles = telencephalon
3rd ventricle = diencephalon
Mesencephalon = Aqueduct
Metencephalon = 4th ventricle
Myelencephalon = 4th ventricla
Spinal chord = central canal

Question 22

When does CSF begin to form?

Answer 22

During the 5th week.

Question 23

What is CSF produced by?

Answer 23

Choroid plexus (3rd, 4th and lateral ventricles)

Question 24

What is Hydrocephalus?

Answer 24

Failure of drainage of CSF (ofen the aqueduct is blocked), meaning that the fluid builds up in the ventricle s and either causes brian to exand (if baby) or pressure in the brain.

Question 25

EVERY TYPE OF NEURAL CELL IS FORMED FOM nEUROEPITHELIAL CELLS EXCEPT FOR…. WHICH IS FORMED BY …..

Answer 25

except for microglial (immune cellsin brain), which are formed from the mesenchyme

Question 26

Wht does the peripheral nervous syeem develop from?

Answer 26

Neural crest cells - the fun ones that want to head off and dot heir own thing

Question 27

Microcephaly, WHat is it, causes,?

Answer 27

Small brian! Can be due to zika virus, drugs or genetic.

Question 28

Aegenesis corpus callosum?, causes and consequences

Answer 28

PArtial or complete absence of Corpus callosum.

Question 29

Porencephaly causesand what is?

Answer 29

CSF filled cysts. Delayed frowth and impairment

Question 30

Schizencephaly causes and what is?

Answer 30

Large clefts/splits in the brain, could be deu to genetic issues/stroke in utero/infection. Causes developmental delay and intellectual impairment.

Question 31

Diastematomyelia

Answer 31

Split of spinal chord longitudinally into 2. Vertebral anomalies. Causes scoliosis/weakness of lower extrematies, back hair tuft, foot deformaties and loss of sensation.

Question 32

When does development of nervoi=us system begin?

Answer 32

3rd week (neural plate)

Question 32

Neural tube closed by

Answer 32

end of 4th week