Neurulation And Nervous System

Question 1

What is neurulation?

Answer 1

Formation of neural tube and early CNS development

Question 2

What is the neural crest?

Answer 2

Formation of the PNS (among other products)

Question 3

During what days does embryonic disc transition from bilaminar to trilaminar?

Answer 3

14-16

Question 4

What two things happen in order for embryonic disc to transition from bilaminar to trilaminar?

Answer 4

Days 14-15: epiblast cells dive through primitive streak, invading hypoblast and form the secondary endoderm
Day 16: more epiblast cells dive through primitive streak and form a new 3rd layer (mesoderm)

Question 5

Formation of a trilaminar embryo eventually leads to what ?

Answer 5

Neurulation and formation of the neural tube and neural crest

Question 6

Trilaminar disc lies between what two things?

Answer 6

Amniotic cavity and chorionic cavity

Question 7

What parts of the body do the following germ layers produce

1. Ectoderm
2. Mesoderm
3. Endoderm

Answer 7

1. Nervous system (via neurulation) and skin
2. Bones, muscle, urogenital organs, mesothelial linings, cardiovascular system
3. GI tract, airway

Question 8

1. When do the prechordal plate and notochordal process form and how?
2. General location of prechordal plate
3. What do notochordal process and prechordal plate form and what is this products function

Answer 8

1. Day 17– another wave of ingressing epiblast cells dive through primitive pit
2. Further cranially
3. Notochord= gives rise to vertebral bodies and induces ectoderm to form neural tube and neural crest

Question 9

1. What are the three plates that the mesoderm splits into?
2. What do each of these plates form?
3. Where is notochordal process located?

Answer 9

1. Paraxial, intermediate and lateral
2. Paraxial- axial skeleton, skeletal muscle and part of dermis
   Intermediate- urogenital systems
   Lateral- most of dermis and lining of body wall; linings of visceral organs
3. At midline, in between these structures (like in between both sides)

Question 10

When the notochordal process fuses with endoderm, it does so in what direction

Notochordal process becomes the ___ which then becomes the ___

Answer 10

Commences at caudal end and proceeds cranially

Notochordal plate —> notochord

Question 11

What does rostral mean

Answer 11

Cranial

Question 12

Prechordal plate and notochordal process induce ectoderm to form ____. How do they do this?

Answer 12

Neural plate (which differentiates into the CNS)
By secreting signals

Question 13

Somites are derivatives of?
Where are they located
What do they help make

Answer 13

Paraxial mesoderm
Just lateral to neural tube
Vertebral column

Question 14

Neural tube is filled with

Answer 14

Amniotic fluid, later replaced by CSF

~neural tube is what the neural plate becomes

Question 15

3 zones of neural tube from exterior to interior

Which zone do neuroepithelial cells undergo mitosis? What forms?

Answer 15

Marginal zone, mantle zone, and ventricular zone

Ventricular zone; forms glioblasts and neuroblasts

Question 16

1. What are neuroblasts?

2. What are glioblasts?

Answer 16

1. Stem cells that form neurons

2. Form glial cells (ependymal and radial glia cells)

Question 17

1. Which plate yields sensory regions of spinal cord?
2. Motor regions?
3. Where do autonomics develop?

Answer 17

1. Alar plate
2. Basal plate
3. Sulcus limitans (kind of centrally located)

Question 18

What is anencephaly and why does it occur?

Answer 18

Failure of entire brain to develop; nerve pores don’t close so brain development does not continue (very small skull)

Question 19

Explain the following of types of herniations that occur due to problems with closure of the skull:

1. Meningocele
2. Meningoencephalocele
3. Meningohydroencephalocele

Answer 19

1. Herniation of meninges
2. Herniation of meninges and brain tissue
3. Herniation of meninges, brain tissue and ventricle

Question 20

Difference between spina bifida cystica and spina bifida occulta

Answer 20

Cystica= herniation of just meninges or meninges and spinal cord into a cyst covered by skin

Occulta= no herniation or formation of cyst; failure of closure of spinal canal but back appears normal

Question 21

What are somites?

What are somites derived from?

What do they subdivide into?

Answer 21

Mature somitomeres

Paraxial mesoderm

Sclerotomes (produce bones) and dermamyotome (dermis and muscles)

Question 22

7 most cranial somitomeres produce what?

How many caudal somites form axial skeleton?

Answer 22

Muscles of face, jaw, and pharynx (CN 5,7,9,10)

34

Question 23

Location of somites?

What do somites form?

Answer 23

On each side of neural tube; just lateral to somites is intermediate mesoderm, and lateral to that is lateral mesoderm

Axial skeleton, ribs, some cranial bones, skeletal muscle and part of dermis

Question 24

IVD if formed from what?

Answer 24

IVD comes from pieces of sclerotome and notochord: sclerotome= annulus fibrosus; notochord= nucleus pulposus

Question 25

Axons are developed from?

Answer 25

Developing motorneurons in spinal cord extending processes through developing vertebrae to myotomes

Question 26

Location of neural crest? Neural crest forms what structures? Neural tube forms what structures?

Answer 26

Between ectoderm and neural tube All components of PNS, cranial nerve ganglia, adrenal medulla, arachnoid and pia mater, and enteric nervous system Spinal cord and brain

Question 27

Where do placodes derive from? Significance of placodes?

Answer 27

Ectoderm (placodes are structures outside of neural tube) Neural crest cells migrate to join the placodes and form sensory neurons and parasympathetic neurons (post-ganglionic)

Question 28

Neural tube has two ends and what in the middle

Answer 28

Cranial and caudal with neural crest cell differentiation in the middle

Question 29

When looking at the caudal end of the neural tube, it has 3 layers. Name them from superficial to deep

Answer 29

Marginal zone, mantle zone, and neuroepithelial zone

Question 30

What else is formed from caudal end

Answer 30

Alar (dorsal) and basal (ventral) plates