Development Of The Central Nervous System FINSIH Flashcards
Define gastrulation
The process whereby the outer layer of the bilaminar disc invaginates at the primaries streak to produce the trilaminar disc
What are the derivates of the ectoderm?
Skin
Nervous tissue
What are the derivates of the mesoderm?
Notochord
Muscles
CVS
What are the derivates of the endoderm?
GI + resp tracts
What is neurulation?
Neural tube formation
Describe the process of neurulation
- induced by notochord
- signals sent to overlying ectoderm to thicken
- neural plate formed
- neural plate starts folding
- fusion of folds in midline > neural tube
- neural tube zips up rostrally + caudally
What does failure of neural tube formation cause?
- if fails in rostral direction: anencephaly
- if fails in caudal direction: spina bifida
What openings are formed in neurulation?
When do they close?
Anterior neuropore - day 25
Posterior neuropore - day 28
What germ layer does the notochord arise from?
Mesoderm
What is the intermediate zone in development of the spinal cord?
Future grey matter
What is the marginal zone in development of the spinal cord?
Future white matter
What are the 3 swellings of the rostrual neural tube?
What do they become?
Prosencephlon > forebrain
Mesencephalon > midbrain
Rhomboencephalon > hindbrain
Subdivision of prosencephalon
What do they become?
- Telencephalon > most of cerebral hemisphere
- Diencephalon > thalamus, hypothalamus + optic nerve/retina
Subdivisions of rhombencephalon
- Metencephalon: pons + cerebellum
- Myelencephalon: medulla
What is spina bifida?
Neural tube defect
Spine + spinal cord do not develop properly in the womb causing a gap in the spine
What is anencephly?
How does it form?
- No brain
- failure of closure of neural tube in cranial direction
- failure of brain to form
What is craniorachischsis?
- Entire neural tube remains open
- failure of brain + spinal cord to form
- Incompatible with life
What is a myelocoele?
What is it due to?
- spinal cord fails to develop
- lumen of neural tube is exposed to outside world
What are children with myelocoele susceptible to?
Meningitis
Due to presence of exposed neural tissue
What is a myelomeningocoele?
What is it due to?
- CSF filled cyst containing spinal cord
- due to failure of development of posterior vertebral arch
Compare transillumination of myelomeningocoele with meningocoele
- meylomeningocoele: poorly due to presence of solid tissue in cyst
- meningocoele: very well
What is a meningocoele?
What is it due to?
- CSF filled cyst
- cord is within vertebral canal
- failure of development of posterior vertebral arch
What is spines bifida occulta?
- only anomaly is lack of posterior vertebral arch
- may have tuft of hair or large naevus/mole over defect
- no significant neurological problems
Prevention of neural tube defects
folic acid
400mg daily from 3 months before conception until week 12 of pregnancy
