Development of the spinal cord

Question 1

process of neurulation results in

Answer 1

results in the formation of the neural tube

Question 2

Describe process of neurulation

Answer 2

• At the notochord at the beginning of neurulation it induces the overlying ectoderm to proliferate.
• This ectoderm with thicken to perform the neural plate. A groove will appear in the midline of the neural plate. This groove is known as the neural groove.
• At the neural groove it invaginates further. The two ends of the neural plate, which are known as neural folds, will move towards each other in the midline of the embryo and they will fuse.
• As they fuse the neural plate will become the neural tube and it will pinch off the rest of the ectoderm.

Question 3

what are neural crest cells

Answer 3

As the neural fold move towards the midline, cells start to detach from them and these cells are known as neural crest cells.

Question 4

what are the three layers of the neural tube?

Answer 4

ependymal layer , mantle layer and marginal layer

Question 5

describe the ependymal layer

Answer 5

inner layer, this layer will form the lining of the central canal of the spinal cord.

Question 6

describe the mantle layer

Answer 6

middle layer, will form of the grey mater of the spinal cord. Consist of closely packed cells. These consist of two cells which can be defined as the neuroblasts (forms the neurons of the spinal cord) and the glioblasts (will form the neuroglial cells- astrocycles, oliogdendrocytes only, not microglia cells)

Question 7

describe the marginal layer

Answer 7

outer layer, will form the white mater of the spinal cord.

Question 8

does the proliferation of the germinal cells in the neural tube result in thickening of the lateral walls?

Answer 8

Yes

Question 9

which layer of the neural tube does the alar and basal plates arise from

Answer 9

mantle layer

Question 10

describe the development of the alar and basal plates

Answer 10

The cells of the mantle plate proliferate profusely and form four bulges which protrude into the lumen and will change the shape and the size of the lumen.
These four bulges separate to form two dorsal bulges (consist of sensory neurons) which are known as the alar plates and two ventral bulges (motor neurons) are known as the basal plates.

Question 11

what is the sulcus limitans

Answer 11

As the alar and basal plates form a cleft will form on either side the lumen of the spinal cord and this cleft is known as the sulcus limitans

Question 12

describe the function of the sulcus limitans

Answer 12

The sulcus limitans separates the cranial nerve motor nuclei from the sensory nuclei.

Question 13

describe “Retraction” of the spinal cord

Answer 13

During early development the neural tube will end the entire length of the embryo, such that the cordal end will lie at the end of the coccyx. By the end of the eighth week the trunk will elongate and the newly developed spinal cord does not keep up with the pace of the trunk and therefore it will be left behind. This will appear as if the newly formed spinal cord is retracting.

Question 14

what are the two different types of spinal bifida

Answer 14

1. Spina bifida occulta
2. Spina bifida cystica (Spina bifida meningocele and Spina bifida with meningomyelocele and Spina bifida with myeloschisis-

Question 15

what causes spinal bifida

Answer 15

This condition is not really as a result of the spinal cord but as a result of the vertebrae which do not fuse properly posteriorly.

Question 16

describe the different types of spinal bifida

Answer 16

1. Spina bifida occulta- no structures protruding. It is characterised by a tuft of hair and a dimple around L5 or S1
2. Spina bifida cystica
   SUBTYPES:
   - Spina bifida meningocele- csf and the meninges will protrude through the defect which forms a cyst
   - Spina bifida with meningomyelocele- produding csf, spinal cord and meninges
   - Spina bifida with myeloschisis- open spinal cord (the neural tube did not close, the two neural folds did not close to form a closed neural tube)