Basic CNS Embryo (Ben)

Question 1

What are the 3 parts of the wall of the neural tube (inner > outer) and what cells/structures are found in them?

Answer 1

1. Ventricular Zone - neuroepithelium here gives rise to all neuroblasts and glioblasts, then becomes ependymal cells
2. Intermediate/Mantle Zone - Neuroblasts and glioblasts migrate here
3. Marginal Zone - Glioblasts migrate here as well and neuroblast axons grow outward toward this zone

Question 2

What kind of cells are found in dorsal root ganglia?

What cells do they develop from and how?

Answer 2

Pseudounipolar Neurons are found in DRG

• develop from Neural Crest Cells, starting first as bipolar neurons and then pinching their two separate processes together so that their cell bodies move peripherally away from the new, single axonal process

Question 3

What cells give the meninges of the spinal cord?

And how do the different layers form?

Also what are the fancy names of the 2 different classifications of meninges?

Answer 3

Neural Crest Cells + Mesenchyme migrate to surround the neural tube.

• external layer thickens to give Dura Mater (AKA Pachymeninx)
• internal layer starts together as Pia-Arachnoid (AKA Leptomeninx) but then separate when fluid cavities form and merge to make the subarachnoid space leaving CT strands between the layers as arachnoid trabeculae

Question 4

Why does the spinal cord not extend through the entire vertebral column in adults, but does in fetuses?

To where does it extend in adults?

And to where do the dura and arachnoid extend?

Answer 4

• vetebra and dura mater grow faster than the spinal cord
• eventually extends only to L1 in adults
• dura and arachnoid extend to S2

Question 5

What is the extension of spinal meninges which goes almost to the end of the spinal column in adults?

What is it made of?

Where does it attach?

Answer 5

the filum terminale made up of pia mater extends out of the dural sac and attaches to coccygeal vertebra 1

Question 6

What is the primary prosencephalon?

Secondary prosencephalon?

Answer 6

Primary Prosencephalon - telencephalon, diencephalon + hypothalmus

Secondary Prosencephalon - only telencephalon + hypothalamus, plus eye cup (no diencephalon)

Question 7

What are the segments of the neural tube called?

How are they subdivided and how many of each subdivision are there?

Answer 7

Neuromeres

• Prosomeres (1-6, increasing in number rostrally from midbrain)
• Mesomeres (only 1)
• Rhombomeres (11 total, increasing in number caudaully from midbrain)

Question 8

How are the neuro- and glioblasts migrating from the ventricular zone of the neural tube wall guided along their path?

Answer 8

they travel along long processes of radial glial cells

Question 9

What embryonic structure gives the striatum?

Answer 9

Lateral Ganglionic Eminence

Question 10

What embryonic structure gives the pallidum?

Answer 10

Medial Ganglionic Eminence

Question 11

What embryonic structure gives the secondary prosencephalon?

Answer 11

the rostral end of the alar plate

Question 12

How far rostrally does the notochord extend as the brain develops?

Answer 12

• only to the level of the mammillary bodies

Question 13

What embryonic structure gives the pre- or subthalamus?

Answer 13

Prosomere 3 (P3)

Question 14

What embryonic structure gives the thalamus?

Answer 14

Prosomere 2

Question 15

What important area separates prosomeres 2 and 3?

What is its importance and what molecular signals does it use?

Answer 15

Zona Limitans

• it is an important organizing center in the development of the diencephalon
• uses SHh and LHX1 signaling

Question 16

What embryonic structure gives the pre-tectum?

And what is the importance of the pre-tectum?

Answer 16

Prosomere 1 (P1)

• pre-tectum also known as pre-tectal area, is an important area in visual processing

Question 17

What embryonic structure gives the tela choroidea?

Answer 17

Roof Plate along the dorsal length of the developing brain

Question 18

What important structure separates the mesomeres from the rhombomeres?

What is its importance and what molecular signaling does it use?

It can also be considered a neuromere… which neuromere?

Answer 18

Isthmus

• an important organizing center of the brainstem between the mesomere and rhombomere 1
• uses FGF-8 signalling
• can be considered Rhombomere 0 (R0)

Question 19

What is the term for the large rostral area of the embryonic brain which gives the telencephalic cortex?

And the general term for all the areas below it which give basal nuclei?

Answer 19

Pallium - gives the telencephalic cortex

Sub-pallium - gives the medial and lateral ganglionic eminences (which give striatum + pallidum) plus the diagonal bend

Question 20

What embryonic structures give the cerebellum?

Answer 20

Alar and Roof Plates of Rhombomere 3

Question 21

What embryonic structures give the pons?

Answer 21

Rhombomeres 3 and 4

Question 22

What embryonic structures does the medulla oblongata arise from?

Answer 22

Rhombomeres 5 and up

Question 23

What prosencephalic area of the embryo develops in between the two hemispheres and gives rise to many interhemispheric connections?

What specific connections does it give rise to?

Answer 23

Telencephalon Impar (meaning “unpaired”)

• the middle region of the telencephalon at the rostral end of ventricle III

Gives rise to:

• Anterior Commissure
• Lamina Terminalis
• Parts of Corpus Callosum
• Pre-optic Area