Embryology of NS

Question 1

What does neural tissue develop from?

Answer 1

Embryonic ectoderm

Question 2

What is neurulation

Answer 2

Formation and development of the neural tube

Question 3

Describe the process of neurolation including time?

Answer 3

• Neural plate forms as a result of thickening of ectoderm anterior to primitive streak
• Thickening of edges of neural plate= neural fold
• Neural folds grow towards each other to form the neural tube
• Neural tube initially stays open at anterior and posterior ends
• Anterior neuropore closes at 25 days (cranial end)
• Posterior neuropore closes at 27 days (caudal end)

Question 4

Which are the main conditions which present as a result of the neural tube not closing

Answer 4

• Spina bifida
• Encephaloceal
• Anencephaly : absence of a major portion of skull/brain

Question 5

On what day does the closure of neural tube usually begin?

Answer 5

18

Question 6

When do the brain vesicles begin to form?

Answer 6

When the anterior neurpore begins to close

Question 7

Which are the first 3 vesicles?

When do they present

Answer 7

In week 4

• Prosencephalon = forebrain
• Mesencephalon
• Rhombencephalon =hindbrain

Question 8

What do the first 3 vesicles further develop into?

Answer 8

In 5th week:

Prosencephalon splits into:

• Telencephalon
• Diencephalon

Rhombecephalon splits into:

• Metencephalon
• Myelencephalon

Question 9

Where is the cephalic flexure and when does it form

Answer 9

Forms between the midbrain and the hindbrain at the end of the 3rd week

Question 10

where is the cervical flexure and when does it form?

Answer 10

• End of 4th week

- Between hindbrain and spinal cord

Question 11

Where is the pontine flexure and when does it form?

Answer 11

• End of 5th week
• In hindbrain
• Between the two components of the hindbrain: myencephalon and metencephalon

Question 12

What does the telencephalon give rise to?

Answer 12

• cerebral hemispheres
• Basal ganglia
• Hippocampus

Question 13

What does the diencephalon give rise to?

Answer 13

• Thalamus
• hypothalamus
• Pineal gland
• Pituitary gland

Question 14

What does the mesencephalon give rise to?

Answer 14

superior and inferior colliculi

Question 15

what does the mesencephalon give rise to?

Answer 15

• pons

- cerebellum

Question 16

what does the myeloencephalon give rise to?

Answer 16

medulla

Question 17

Production of the CSF

Answer 17

Begins to be produced in 5th week
Mainly via lateral ventricles
Moves into subarachnoid space through the roof of the 4th ventricle

Question 18

Cellular differentiation

Answer 18

• Begins In embryonic stage and continues in post-natal stage
• Neural tube made up of rapidly dividing neuroepithelium
• Divides at the ventricular surface
• Neuroepithelium divides into neurones, astrocytes, oligodendricites, ependymal cells
• Exception are mesenchymal cells which form from microglia which migrate into CNS
• Neural crest gives rise to the cells of the PNS

Question 19

Spinal cord development

Answer 19

• Sensory component of spinal nerves: dorsal root ganglion from neural crest
• Motor component: from the neural tube

Positional changes

• At 3rd month the spinal cord extends the whole length of the spinal cord
• However the vertebral column and the dura mater grow faster than the spinal cord which explains why the spinal cord ends at a higher level than them
• The remaining space in the vertebral column is made up form caudal equina and filum terminal

Question 20

Cortical folding

Answer 20

• Brings cerebral hemispheres closer together
• Connects part of the brain which would otherwise be far away
• Folds= sulci
• Overlying surface= gyrus