Neurulation

Question 1

What is neurulation?

Answer 1

First step in development of CNS

Question 2

How is neurulation initiated?

Answer 2

By signals from notochord - cause overlying ectoderm to thicken and form neuroectoderm which gives rise to neural plate

Question 3

What happens as ectoderm continues to thicken?

Answer 3

Lateral edges of neural plate begin to elevate and form neural folds. Folds get closer together and fuse to form neural tube

Question 4

What forms between folds before fusing?

Answer 4

Neural groove

Question 5

What does neural tube go on to form?

Answer 5

Spinal cord and brain

Question 6

Where does fusion of neural folds begin?

Answer 6

In cervical (neck) region

Continues cranially and caudally

Question 7

As the neural folds fuse, what happens to the neural tube?

Answer 7

It separates from surface ectoderm

Question 8

The cranial and caudal ends then need to fuse to form a sealed tube. In what direction does this fusing happen?

Answer 8

Cranially to caudally

Question 9

Where is the anterior neuropore found?

Answer 9

Cranial end

Question 10

What day does the anterior neuropore fuse?

Answer 10

Day 25

Question 11

What will the anterior neuropore form?

Answer 11

The brain

Question 12

Where is the posterior neuropore found?

Answer 12

Caudal end

Question 13

What day does the posterior neuropore fuse?

Answer 13

Day 28

Question 14

What will the posterior neuropore form?

Answer 14

The spinal cord

Question 15

Why is the fusion of these neuropores important?

Answer 15

Amniotic fluid can damage them once nervous system forms

Question 16

What can decrease the risk of neural tube defects?

Answer 16

Folic acid

Question 17

What is the failure of the fusion of the anterior neuropore called?

Answer 17

Anencephaly

Question 18

What happens during anencephaly?

Answer 18

Neural tube is open to amniotic cavity and fluid can damage formation of neural tissue - prevents proper formation of brain (forebrain doesn’t form)

Question 19

What is effects of anencephaly?

Answer 19

Affects cognition, memory, speech, vision, hearing

Question 20

What is the failure of the fusion of the posterior neuropore called?

Answer 20

Rachischisis

Question 21

What happens during rachischisis?

Answer 21

Spinal cord doesn’t form properly - open neural tube presents formation of vertebrae
- flat plate of neural tissue exposed at birth

Question 22

What does rachischisis lead to?

Answer 22

High risk of infection as CNS exposed to external environment - paralysis, motor and sensory dysfunction

Question 23

Why is spina bifida technically not a neural tube defect?

Answer 23

Neural tube forms fine but it is actually the vertebrae (and vertebral arch) that doesn’t form correctly

Question 24

How are neural crest cells formed?

Answer 24

As neural folds elevate and fuse, the cells at the lateral edges separate from the neural tube

Question 25

What happens to these neural crest cells after separating from the neural tube?

Answer 25

They migrate laterally and ventrally, dispelling widely and surrounding the embryo.

They differentiate into a variety of structures throughout the body

Question 26

What are neural crest cells sometimes referred to as?

Answer 26

4th germ layer

Question 27

The neural tube then separates from the surface ectoderm. Why is this separation important?

Answer 27

Surface ectoderm goes on to form skin

Question 28

What is neurofibromatosis?

Answer 28

Genetic condition caused by mutation in neurofibromin1 (NF1) gene
- Tumour supressor gene that is switched off in this mutation

Question 29

What is the effects of neurofibromatosis?

Answer 29

Increased cell division - benign tumours of the nervous system, skin, cranial bones