Embryo - Brain, add. to Ben's basics

Question 1

Which flexures does the embryonic brain form during its development?

Answer 1

in rostrocaudal direction

1. cephalic flexure (ventral)
2. pontine flexure (dorsal)
3. cervical flexure (ventral)

Question 2

Which structures are formed in the open part of the myelencephalon?

Answer 2

• neural tube in medulla → canalis centralis
• neuroblasts from alar plate → ncl. gracilis/cuneatus

Question 3

Which structures are formed in the closed part of the myelencephalon?

What is important to mention though?

Answer 3

alar plates grow laterally due to forming pontine flexure

• alar plates → sensory ncll. (laterally) + olivae
• basal plates → motor ncll. (medially)

BUT: SM ncll. mostly belong in 1 rhombomere, BM in 2

Question 4

Which zone of the rhombencephalon is responsible for the development of the cereballar cortex + ncll.?

Which further structures are formed?

Answer 4

mantle zone

also form: pont. ncll., cochlear, trochlear ncll., sensory part of n. V

Question 5

How do the choroid plexus form in the all ventricles?

Answer 5

pia mater covering the ependymal layer invaginates

→ plexus choroideus

_{<u>BUT: </u>only ventricular fluid produced by plexus choroideus, brain + leptomeninx add substances to produce CSF}

Question 6

How do the Pacchioni granules develop?

Answer 6

from epithelium of arachnoidea + sinal endothelium

Question 7

How does the pituitary gland develop?

Answer 7

derives from 2 swellings

• Rathke pouch (= hypophysial diverticulum, ant.) develops as upgrowth of ectodermal roof of stomodeum, degenerates later → glandular adenohypophysis
• neurohypophysial diverticulum develops from neuroectoderm of terminal hypothalamus

Question 8

What are the main secondary organizing centers in the brain?

Explain their function.

Answer 8

⇒ determine rostrocaudal regionalization of the brain

• ant. neural ridge: ant. border of neural plate, antagonizes caudalization signals (e.g. Wnt) and promotes prosenc. factor Six3
• zona limitans: border P2/3
• isthmic organizer: pros-/rhombencephalic border, produces Fgf8 for r1 (cerebellar dev.) and Wnt1 for mesencephalon (dev. of colliculi)

Question 9

Which structure borders p1/2?

Answer 9

fasc. retroflexus (MEYNERT)

Question 10

Which rhombomeres are referred to as pseudorhombomeres?

Answer 10

r7 - 11

Question 11

Which transcription factors are required for the successful regionalization of the neural tube?

They are produced by… ?

Answer 11

• non-neural ectoderm → BMPs
• notochord + floor plate → Shh
• somites → retinoic acid
• roof plate, later alar plate → Pax 3,7
• basal plate → Nkx, later Pax 6

​_{somites = S}