CNS Development 1- Development of the Spinal Cord

Question 1

Purpose of neurulation

Answer 1

Marks the beginning of the formation of the CNS

Process whereby the neural plate forms the neural tube

Question 2

Process of neurulation

Answer 2

Notocord triggers ectoderm to thicken to form neural plate
Week 3, neural plate elevates to form neural folds with the neural groove in the middle of the folds
The neural folds fuse together to create the neural tube
Some cells on the top of the neural tube detach and are lost, forming the neural crest cells
Notocord only induces the ectoderm that lies above it, the rest of the uninduced ectoderm will become surface epithelium which forms the epidermis of the skin

Question 3

Neural crest cells

Answer 3

Start the formation of the PNS

Question 4

Cranial and caudal neuropores

Answer 4

Neural tube remains open at both ends
Close before termination of CNS formation
Cranial half forms brain
Caudal half forms spinal cord

Question 5

Neural tube constituents

Answer 5

Layer of simple squamous epithelium known as germinal cells

Proliferate to form pseudostratified layers with lateral thickening

Question 6

Layers of neural tube after proliferation

Answer 6

Ependymal
Mantle
Marginal

Question 7

Ependymal layer

Answer 7

Simple columnar epithelium

Forms lining of central canal

Question 8

Mantle layer

Answer 8

Forms grey matter

Consists of closely packed germinal cells

Question 9

Marginal layer

Answer 9

Forms white matter

Contain axons which extend from neurons positioned in mantle layer

Question 10

Germinal cells

Answer 10

Neuroblasts- will form the neurons of the spinal cord

Glioblasts- will form the neuroglia cells (astrocytes and oligodendrocytes only)

Question 11

Microglia formation

Answer 11

From the mesenchyme of surrounding blood vessels

Question 12

Outer layer of neural tube

Answer 12

Consists of vascular mesenchyme containing neural crest cells
Responsible for formation of meninges and spinal cord

Question 13

Formation of alar and basal plates

Answer 13

Cells of mantle layer proliferate to form 4 bulges by protruding into lumen
Form bilateral alar and basal plates separated by an intermediate plate

Question 14

Alar plates

Answer 14

Sensory neurons

Question 15

Basal plates

Answer 15

Motor neurons

Question 16

Sulcus limitans

Answer 16

Cleft formed on either side of the lumen by the separation of the alar and basal plates
Function is to divide the spinal cord into two anatomical and functional parts (motor and sensory)
Extends entire length of neural tube

Question 17

Retraction of the spinal cord

Answer 17

In early development, neural tube extends entire length of embryo so the cordal end lies at the end of the coccyx
End of week 8, the trunk elongates but the spinal cord does not keep up with the rate of elongation and is therefore left behind
Therefore appears as if cord is retracting

Question 18

Spina bifida

Answer 18

As a result of poor fusion of the spinal vertebrae posteriorly
Spina bifida occulta
Spina bifida cystica

Question 19

Spina bifida occulta

Answer 19

No structures protruding

Tuft of hair and dimple at L5/S1

Question 20

Spina bifida cystica subtypes

Answer 20

Spina bifida meningocele- CSF and meninges
Spina bifida with meningomyocele- CSF, meninges and spinal cord
Spina bifida with myeloschisis- open spinal cord, neural folds did not close when forming neural tube