Development of Spinal Cord

Question 1

The spinal cord develops from the caudal part of the neural tube (caudal to the ——- pair of somites).

Answer 1

fourth

Question 2

Somite develop from ———-

Answer 2

Paraxial mesoderm

Question 3

Changes occurring in the wall of the neural tube
o ——-shaped lumen of the neural tube becomes circular> ————
o The Neuroepithelial cells form the thickness of the neural tube.
o They continue proliferating to form the neuroepithelium.
o Once neural tube is closed, the cells form the ———-.
o Neuroblast forms the Mantle layer> grey matter.
o Nerve fibers in the Outermost layer forms the Marginal layer> white matter (appears white after —)

Answer 3

Diamond
circular canal
neuroblast
myelination

Question 4

Changes occurring in the wall of the neural tube
o Mantle layer shows —— and —— thickening
o Ventral thickening forms the ——— forming the motor area(motor neurons).
o Dorsal thickening forms the —- forming the sensory area.
o ———- marks the boundary between alar & basal plates.
o An intermediate horn between the ventral & dorsal horns in the region (T1—L2) containing neurons of ——- system
o Roof and floor plates are dorsal & ventral areas of the tube with NO ——

Answer 4

dorsal - ventral
basal plate
alar plate
Sulcus limitans
sympathetic
neurons

Question 5

Changes occurring in the wall of the neural tube
o —— layer derived from neuroepithelial cells lines the central canal.
o Occlusion of the dorsal part of the central canal> —- septum
o Bulging of the 2 basal laminae more than the floor plate> ——-

Answer 5

Ependymal
postromedian
antromedian fissure

Question 6

Development of the dorsal horn

1. • It is the dorsolateral thickening of the mantle layer.
   • It gives rise to sensory neuroblasts of the dorsal horn {GSA}.
   • It receives axons, which become the dorsal roots, from the dorsal root ganglion.
   • It becomes the dorsal horn of the spinal cord

Answer 6

Alar plate

Question 7

Development of the dorsal horn

2. • It is the ventrolateral thickening of the mantle layer.
   • It gives rise to motor neuroblasts of the ventral and lateral horns regions.
   • Axons from motor neuroblasts exit the spinal cord and form the ventral roots.
   • It becomes the ventral horn of the spinal cord.

Answer 7

Basal plate

Question 8

3.————
oIt appears during the —— week of development.
oIt is a longitudinal groove in the neural tube.
oIt separates the alar (sensory) and basal (motor) plates.
oIt extends from the spinal cord to the rostral midbrain.
oIt ——- in the adult spinal cord.
o It is retained in the rhomboid fossa of the brain stem as the superior and inferior ———.

Answer 8

Sulcus Limitans
4th
disappears
fovea

Question 9

- It is the non-neural roof of the central canal, which connects the two alar plates

Answer 9

-Roof plate

Question 10

5. • It is the non-neural floor of the central canal, which connects the two basal plates.
   • It contains the ventral white commissure

Answer 10

-Floor plate

Question 11

Myelination

• Commences in the ——- fetal month
• Myelination of —— fibers is earlier than —— fibers.
  1. Oligodendrocytes accomplish myelination of the CNS.
  2. Schwann cells accomplish myelination of the PNS

Answer 11

4th
motor
sensory

Question 12

Myelination of the ——— tracts is not
completed until the end of the first postnatal year
(i.e., ——– tracts become functional).

Answer 12

corticospinal

corticospinal

Question 13

The roots of the spinal nerve
——- root:
is derived from elongating axons of neurons in the basal plate Dorsal root
• Originate from the central process of cells in the dorsal root ganglia (DRG).
• While distal process join the ventral nerve roots to form the spinal nerve
• Cells of DRG are derived from the ———-

Answer 13

Ventral

neural crest cells

Question 14

Prenatal Positional changes of spinal cord
oAt the 8th——12th week(3rd month), the spinal cord extends through the ——- length of the vertebral
canal.
oSpinal nerves passes —– through intervertebral foramina at their level of origin.

Answer 14

whole

horizontally

Question 15

Prenatal Positional changes of spinal cord
- With increasing age the vertebral column &
dura lengthen more rapidly than the neural tube.
- The terminal end of the spinal cord shifts to a higher level.
results in………..
At birth
- the conus medullaris extends to the level of
the——————
- Spinal nerves run obliquely from their
segment of origin to the corresponding level
of the vertebral column.
- The dura is attached to the ———–

Answer 15

3rd lumbar vertebra (L3).

coccygeal level.

Question 16

Prenatal Positional changes of spinal cord
In adults:
- Spinal cord ends the lower border of——
-Dural sac & subarachnoid space extend till ————–
-Formation of the cauda equina which consists of dorsal and ventral roots, that descends below the level of the ———-.
- Thread like extension of the pia matter (————–)
remains attached to the coccygeal level

Answer 16

L1
S2-3
conus medullaris
filum terminale

Question 17

Congenital malformations
Causes:
• failure of neural tube to ——
• failure of neural tube separate from the surface
———-
• failure of vertebral arches to fuse.=————–

Answer 17

close
ectoderm
Spina bifida

Question 18

Congenital anomalies
Spina Bifida
Usually occurs in the ----------region.
- It includes the following variations:
1. Spina bifida occulta
2. Spina bifida with meningocele
3.Spina bifida with meningomyelocele
4. Spina bifida with myeloschisis

Answer 18

sacrolumbar

Question 19

1. Spina bifida ———–
   - It is a defect in the vertebral arches.
   - It is the least severe variation.
   - It occurs in 10% of the population

Answer 19

occulta

Question 20

2. Spina bifida with ——–
   - It occurs when the meninges project through a
   vertebral defect, forming a sac filled with CSF.
   - It exists with the spinal cord remaining in its normal
   position
   dura and subarachnoid space containing CSF the SC is intact

Answer 20

meningocele

Question 21

3. Spina bifida with ——————-
   It occurs when the meninges and spinal cord project
   through a vertebral defect, forming a sac

Answer 21

meningomyelocele

Question 22

4. Spina bifida with ———- (spinal cord cleft)
   name on photo Rachischisis
   - It is the most severe type of spina bifida.
   - It results in an open neural tube that lies on the surface of the back.

Answer 22

myeloschisis