Embryology of the CNS

Question 1

Define Neurulation

Answer 1

The formation in the early embryo of the neural plate and neural folds, followed by its closure with development of the neural tube.

Question 2

When in embryological development does the neurulation occur?

Answer 2

Week 3 - middle of week 4

Question 3

Describe the formation of the neural plate during neurulation

Answer 3

The dorsal midline ectoderm undergoes thickening to form the neural plate

Question 4

Describe the formation of the neural folds and groove during neurulation, from the neural plate

Answer 4

The lateral margins of the neural plate become elevated, forming neural folds on either side of a longitudinal, midline depression, the neural groove

Question 5

Describe the formation of neural crests during neurulation

Answer 5

Some cells of the apices of the neural folds become separated to form groups lying dorsolateral to the neural tube - the neural crests.

Question 6

Label the diagrams of neurulation

Answer 6

Question 7

What happens to the neural tube once formed?

Answer 7

A longitudinal groove, the sulcus limitans, appears on the inner surface of the lateral walls of the neural tube dividing it into ventral and dorsal sections

Question 8

Describe what happens to the neural tube after the formation of the sulcus limitans

Answer 8

The ventral portion, basal plate become motor neurones

The dorsal portion, the alar plate, become sensory neurones

Question 9

At what week of development do the primary brain vesicles form from the neural tube, and what are they?

Answer 9

At week five the rostral portion of the neural tube forms the:

• Prosencephalon (forebrain)
• Mesencephalon (midbrain)
• Rhombancephalon (hindbrain)

Question 10

What separates the Prosencephalon from the Mesencephalon?

Answer 10

The Cephalic flexure

Question 11

At what week of development do the secondary brain vesicles form, and what are they?

Answer 11

At week 7 secondary brain vesicles are formed

Prosencephalon

• >Telencephalon
• > Diencephalon

Rhombancephalon

• > Metencephalon
• > Myelencephalon

Question 12

What sepparated the Metencephalon and the Myelencephalon?

Answer 12

The formation of teh pontine flexure

Question 13

Which derivates of in the mature brain do each secondary brain vesicle form?

(i) Telencephalon
(ii) Diencephalon
(iii) Mesenchephalon
(iv) Metencephalon
(v) Myelencephalon

Answer 13

(i) Cerebral hemispheres
(ii) Thalamus
(iii) Midbrain
(iv) Pons, cerebellum
(v) medulla oblongata