ANS 123 - Neurulation

Neurulation

formation of spinal cord precursors from epiblast

induction events and formation of neural tube

When does neurulation occur?

end of gastrulation, as primitive streak regresses

where does central nervous tissue develop from?

ectoderm origin

how does neurulation begin and end?

begins with 1st traces of neural plate cells

ends with closure of neural tube

after notochord is formed during regression, how are neural plate cells formed?

notochord sends signals to epiblast cells to become plate cells

Morphogenesis

Generation, differentiation & growth of tissues and organs during development; process through which organisms take on shape

what is the neural tube a rudiment of?

CNS

what does the neural tube eventually become?

adult brain and adult spinal column

the process of neurulation is specific to ___

chordates

notochord

temporary rod of mesoderm under midline of epiblast that triggers neural tube formation

notochord is activated by what?

induction messages from hensen's node as it moves backward

what doe notochord formation induce?

once formed it sends signals back up to epiblast ectoderm to initiate CNS formation - neural plate

is notochord a temporary structure?

yes

true or false: notochord may be involved in bone structure of spinal column

true

primordial CNS orgin

ectoderm

How does primordial CNS form

via invagination

1. notochord induces epiblast ectoderm -> form neural plate cells

2. bending of neural plate into neural groove

3.closure/pinch off neural groove (separate from ectoderm) into neural tube

neural crest cells

Cells at the tip of the neural fold; sluff off upon invagination into blastoceal

sequence of neurlation events happen in which direction?

anterior -> posterior

Describe sequence of events for neurlation.

1. during ingression epiblast cells differentiate into mesoderm within blastocel

2. hensen's node at anterior most portion of primitive streak activates mesoderm to form notochord during regression

3. notochord messages to ectoderm to determinate & differeniate into neural plate cells

4. invagination of neural plate into groove, pinching off and form neural tube

5. neural tube becomes CNS

what does the anterior most part of neural tube become?

thickening and constrictions via cell division - presumptive brain @ 3 weeks

what does the posterior most part of neural tube become?

stays tube like - spinal chord

what three vesicles from the presumptive brain?

prosencephalon (forebrain anterior)

mesencephalon (midbrain)

rhombencephalon (hind brain posterior)

Which one of the three layers does not split>

mesencephalon

three vesciles in brain become five, what are they?

- prosencephalon (forebrain) -> telencephalon & diencephalon

- mesencephalon

- rhombencephalon -> metencephalon & myelencephalon

walls of the neural tube are made from which germ layer?

ectoderm

why does the prosencephalon have two blob shape?

important structure for eyes -> send signals to formulate brain tissue for optic nerve -> retina

the walls of the presumptive brain eventually become what?

the actually brain parts we know like cerebrum

the cavities of the presumptive brain eventually become what?

ventricles