Development Of The Central Nervous System FINSIH

Question 1

Define gastrulation

Answer 1

The process whereby the outer layer of the bilaminar disc invaginates at the primaries streak to produce the trilaminar disc

Question 2

What are the derivates of the ectoderm?

Answer 2

Skin
Nervous tissue

Question 3

What are the derivates of the mesoderm?

Answer 3

Notochord
Muscles
CVS

Question 4

What are the derivates of the endoderm?

Answer 4

GI + resp tracts

Question 5

What is neurulation?

Answer 5

Neural tube formation

Question 6

Describe the process of neurulation

Answer 6

• 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

Question 7

What does failure of neural tube formation cause?

Answer 7

• if fails in rostral direction: anencephaly
• if fails in caudal direction: spina bifida

Question 8

What openings are formed in neurulation?
When do they close?

Answer 8

Anterior neuropore - day 25
Posterior neuropore - day 28

Question 9

What germ layer does the notochord arise from?

Answer 9

Mesoderm

Question 10

What is the intermediate zone in development of the spinal cord?

Answer 10

Future grey matter

Question 11

What is the marginal zone in development of the spinal cord?

Answer 11

Future white matter

Question 12

What are the 3 swellings of the rostrual neural tube?
What do they become?

Answer 12

Prosencephlon > forebrain
Mesencephalon > midbrain
Rhomboencephalon > hindbrain

Question 13

Subdivision of prosencephalon
What do they become?

Answer 13

• Telencephalon > most of cerebral hemisphere
• Diencephalon > thalamus, hypothalamus + optic nerve/retina

Question 14

Subdivisions of rhombencephalon

Answer 14

• Metencephalon: pons + cerebellum
• Myelencephalon: medulla

Question 15

What is spina bifida?

Answer 15

Neural tube defect
Spine + spinal cord do not develop properly in the womb causing a gap in the spine

Question 16

What is anencephly?
How does it form?

Answer 16

• No brain
• failure of closure of neural tube in cranial direction
• failure of brain to form

Question 17

What is craniorachischsis?

Answer 17

• Entire neural tube remains open
• failure of brain + spinal cord to form
• Incompatible with life

Question 18

What is a myelocoele?
What is it due to?

Answer 18

• spinal cord fails to develop
• lumen of neural tube is exposed to outside world

Question 19

What are children with myelocoele susceptible to?

Answer 19

Meningitis
Due to presence of exposed neural tissue

Question 20

What is a myelomeningocoele?
What is it due to?

Answer 20

• CSF filled cyst containing spinal cord
• due to failure of development of posterior vertebral arch

Question 21

Compare transillumination of myelomeningocoele with meningocoele

Answer 21

• meylomeningocoele: poorly due to presence of solid tissue in cyst
• meningocoele: very well

Question 22

What is a meningocoele?
What is it due to?

Answer 22

• CSF filled cyst
• cord is within vertebral canal
• failure of development of posterior vertebral arch

Question 23

What is spines bifida occulta?

Answer 23

• only anomaly is lack of posterior vertebral arch
• may have tuft of hair or large naevus/mole over defect
• no significant neurological problems

Question 24

Prevention of neural tube defects

Answer 24

folic acid
400mg daily from 3 months before conception until week 12 of pregnancy