development of the NS

Question 1

what are the 3 layers of the embryonic disc?

Answer 1

ectoderm,
mesoderm,
endoderm.

Question 2

what is the function of the notochord?

Answer 2

to support the embryo as it is a midline structure.

to stimulate the conversion of overlying surface ectoderm into neuroectoderm.

Question 3

what is neuralation?

Answer 3

the process of neural tube formation.

Question 4

what happens on day 17 after fertilisation?

Answer 4

1. neurulation begins.
2. the notochord induces the ectoderm to form the neural plate.
3. the neural plate begins to bend, forming the neural groove as it does so.
4. the neural folds begin to fuse together, forming the neural tube.
5. the neural tube separates from the surface ectoderm.

Question 5

what is the neural canal?

Answer 5

the hole in the middle of the neural tube.

Question 6

what are the 2 holes at either end of the neural tube called? and what day do they close?

Answer 6

anterior neuropore = closes on day 24.
posterior neuropore = closes on day 26.

Question 7

the cephalic part of the neural tube forms what?

Answer 7

the brain.

Question 8

the caudal part of the neural tube forms what?

Answer 8

the spinal cord.

Question 9

what does the neural canal become?

Answer 9

the ventricular system.

Question 10

what is spina bifida caused by?

Answer 10

incomplete closure of the spinal cord.

Question 11

what is exencephaly caused by?

Answer 11

failure of closure of the anterior neuropore.

Question 12

what is microcephaly caused by?

Answer 12

small brain in small cranium.

Question 13

where are neural crest cells located?

Answer 13

at the border of the neural plate

Question 14

what happens to neural crest cells when the neural tube closes?

Answer 14

the neural crest cells disconnect from the surface ectoderm so they are now located between the surface ectoderm and the neural tube.

as a result, the neural crest cells can migrate to diff locations.

Question 15

what are the 2 parts that the ectoderm is divided into?

Answer 15

1. neuroectoderm.
2. surface ectoderm.

Question 16

what are the derivatives of the neuroectoderm

Answer 16

neural tube - which forms the CNS.

neural crest cells - which forms bones, gangion of cranial nerves, DRG, autonomic ganglion, meninges, Schwann cells and satellite cells.

Question 17

what are the derivatives of the surface ectoderm?

Answer 17

epidermis, hair, nail, and enamel.

anterior lobe of the pituitary gland.

Question 18

what are the 3 primary vesicles of the SC?

Answer 18

1. prosencephalon.
2. mesencephalon.
3. rhombencephalon.

Question 19

what are the 5 secondary vesicles of the SC?

Answer 19

1. telecephalon.
2. dicephalon.
3. mesencephalon.
4. metencephalon.
5. myelencephalon.

Question 20

cranial nerves are completely formed at what week?

Answer 20

7

Question 21

the optic stalk develops into …?

Answer 21

the optic nerve.

Question 22

process of the SC developing:

Answer 22

1. after closure of neural tube, neuroepithelial cells divide rapidly and give rise to primitive nerve cells or neuroblasts.
2. neural blasts form mantle zone which later forms grey matter.
3. marginal layer consists of nerve fibres emerging from neuroblasts in the mantle layer.
4. marginal layer later forms white matter.

Question 23

so which 3 layers is the wall of the neural tube divided into?

Answer 23

1. neuroepithelial.
2. mantle.
   marginal.

Question 24

what is the outermost layer of the neural tube?

Answer 24

the marginal layer.

Question 25

what is the middle layer of the neural tube?

Answer 25

the mantle layer.

Question 26

what is the innermost layer of the neural tube?

Answer 26

neuroepithelial layer.

Question 27

the alar plate undergoes which type of thickening?

Answer 27

dorsal

as it is sensory

Question 28

the basal plate undergoes which type of thickening?

Answer 28

ventral

as it is motor.

Question 29

what landmark marks the boundary between the basal and alar plate?

Answer 29

the sulcus limitans