Nervous System Development III: Brain Development

Question 1

1) What are the Primary Vesicles?

2) What is each primay Vesicle called?

Answer 1

1)The Primary Vesicles are Three Swellings occuring on the part of the Neural tube cranial to the 4th pair of somites.

2)From Cranial to Caudal direction the names of the three primary vesicles:
Prosencephalon -Mesocephalon -Rhombocephalon.

Question 2

When do the Secondary Vesicles form and what do they form in the future?

Answer 2

The development occurs during the 5th week.

The Prosecephalon will form:

1: Telencephalon (will form cerebral hemispheres)
2: Diencephalon 

The Mesoncephalon will not divide.

The Rhombocephalon will divide into:

1: Metancephalon (will form Pons and Cerebrum)
2: Myelencephalon (will form Medulla Oblongata)

Question 3

Discuss the Brain Flexures which develop in the Neural Tube.

Answer 3

During the 5th Week, due to Rapid growth of some areas we see the development of:

1: Midbrain Flexure
2: Cervical Flexure - btw the Brain stem and the Spinal Cord.

Due to the Rapid Growth in the Flexures we see the development of another Flexure on the opposite side called the “Pontine Flexure”

Question 4

What does the Rostral Part of the Myelencephalon Form

Answer 4

• Forms the “Open Part of Medulla Oblongata” and the “Inferior part of the 4th Ventricle.”
• The Alar plate (lateral) and Basal Plate are seperated by the Sulcus Limitans.
• Basal forms Motor Neurons, Alar forms Sensory Neurons.

Question 5

Where does the Olivary Nuclie Develop from?

Answer 5

-Nuclie of the Alar Plate move ventrally to form the Olivary Nuclie.

Question 6

What does the Basal Plate of the Rostral Part of Myelencephalon Form?

Answer 6

From Medial to Lateral.

1) Somatic Efferent
2) Special Visceral Efferent
3) General Visceral Efferent

Question 7

What does the Alar Plate of the Rostral Part of the Myelencephalon form?

Answer 7

From Medial to lateral.

1) Somatic Afferent
2) Special Visceral Afferent
3) General Visceral Afferent

Question 8

What forms up the Tela Choroidea?

Answer 8

The Tela Choroidea is formed from the:

• Roof Plate (single Ependymal Cells)
• Vascular Mesenchyme above (Pia mater).

Question 9

Explain the Formation of Important structures in the Caudal part of the Myelencephalon.

Answer 9

1) Gracile and Cuteneus Nuclie formed by:
- Neuroblasts migrating from Alar Plate to Marginal Zone.

2) Pyramids:
- Formed by fibres crossing at the ventral part of the Medulla.

Question 10

What does the “Metencephalon” form

Answer 10

The Metencephalon will form the:

• Pons
• Cerebellum
• Superior Part of the Fourth Ventricle.

Question 11

Explain the Formation of the General Structure of the Cerebellum.

Answer 11

1) Cerebellar Swellings develop on the Dorsal part of the ALAR Plate.
2) These project into the 4th Ventricle.
3) They fuse together (due to deepening of the Pontine Flexure) in the Midline to form -CEREBELLAR PLATE.
4) The Cerebellar Plate shows a Midline Portion called Vermis and 2 lateral Hemispheres.
- A transverse Fissure seperates the Nodule from Vermis and Floculus from the Hemisphers. Forming the Floculonodular Lobe.

Question 12

How does the Cerebellar Cortex develop?

Answer 12

-It develops from Neuroblasts in the INTERMEDIATE zone of the Alar Plates going to the Medial Part.

Question 13

Explain the Formation of the Pons.

Answer 13

The Marginal Layer of the Metanecephalon expands to accomadate the fibres running from Cerebrum and Cerebellum.

Question 14

Explain the Formation of the Superior/Inferior Colliculus?

Answer 14

Develops from Neuroblasts migrating from alar Plate to the Tectum.

Question 15

What does the Basal Plate of the Mesencephalon Form?

Answer 15

The Basal Plate will have Neuroblast migrating from it to the Tegmentum to form group of Nuclie (Red, CNIII,IV)
and also Substancia Niagra.