Lecture 8: Neurulation and Neural Crest Flashcards Preview

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When are the Central Nervous System and Neural Crest cells developing?

Week 3


How does the notochord induce the neural plate?

Release of Sonic Hedgehog


What are the steps of Neurulation?

(Try to describe it to yourself)

Notocord releases Sonic Hedgehog

Neural Plate is induced

Neural Plate folds inward to form the Neural Fold, and then the Neural Groove

The the Neural Groove pinches off to become the Neural Tube, and the Neural Crest pinches off to float above it.

The Neural Crest cells migrate away.


After Neurulation, what three types of Ectoderm are we left with?

1. Neural Ectoderm

(Neural Plate → Folds → Tube)

2. Surface Ectoderm

The Ectoderm that is left on top after the neural ectoderm enters the mesoderm layer

3. Neural Crest


What is the clinical significance of the number of somites in an embryo?

You can tell how old the embryo is with ultrasound by counting the number of somites.


On what day does the Rostral Neural Pore close?

Day 25


On what day does the Caudal Neuropore close?

Day 28


What is Primary vs Secondary Neurulation?

Primary Neurulation is the complete formation (and closure) of the Neural Tube for the Brain, Cervical, Thoracic, and Lumbar regions.

Secondary Neurulation is the fusion of the Caudal Eminance with the Caudal Neuropore (gives rise to the sacral and coccygeal regions of the spinal cord)


What regions of the embryo primarily have the Neural Crest cells present?

Cranial and Trunk Regions


What type of neurons do the Neural Crest cells give rise to?

Sensory neurons


What specific structures do Neural Crest cells give rise to?

(Just an overview)

Dorsal Root Ganglia (sensory)

Sensory Cranial Nerves (5,7,9,10)

Autonomic Ganglia

Schwann Cells (neurilemma) / Satellite cells

Pia / Arachnoid mater


Cromaffin Cells of Adrenal Glands

Bone and Cartilage of the Face

Aortic arches

Enamel and Dentin of the Teeth


What do we call diseases related to the Neural Crest?



What is Hirschsprung's Disease?

A Neurocristopathy where an infant can develop Megacolon

(no autonomic innervation to the colon)


What is the common cause for all forms of Spina Bifida?

Failure of the Caudal Neural Pore to close at the appropriate time


List the defining characteristics for

Spina Bifida Occulta

Spina Bifida Occulta

Incomplete formation of the vertebral lamina and a gap where the spinous process should be.

Caudal Neural Pore closed too slowly

Common (10% of the population)

Hair on lower back sometimes


List the defining characteristics for



Caudal Neural pore closed WAY too slowly, so there are no vertebral arches, and the meninges and CSF protrude into the back.

Patient may or may not have deficit. 


List the defining characteristics for



Spinal cord exists intact, but is located out in a CSF filled cyst.

Patients do have defects


List the defining characteristics for



There is no cyst here, but the spinal cord presents open on the back.

Patients do have motor and sensory deficits.


What might increased levels of Alpha-Fetoprotien in a pregnant woman indicate?

Either a Meningocele / Meningomyelocele / Meylocele 

or Anencephaly.

Note: Spina Bifida Occulta is not an "open" neural tube defect, and will not show increased alpha-fetoprotien as the other three will.


What nutrient can prevent Neural Tube defects?



What embryological mistake can cause anencephaly?

What are the results?

Failure of the Rostral Neural Tube to close

Lack of a neocortex, risk for infection. Results in death shortly after birth.


Besides Anencephaly, what other two defects we talked about can arise from a failure of the Rostral Neural Pore to close?

Encephalocele with Brain tissue

Depending on the severity, can cause neurological defects.


Encephalocele without Brain tissue

Patients can be normal.



What gives rise to the Meninges?


What is it made of?

The Meninx Primitiva


Mesoderm - specifically Pariaxial Mesoderm (Sclerotome)


Neural Crest Cells


What two cell populations come from the Meninx Primitiva?

What are they made of, and what do they make?

1. Pachymeninx

Mesoderm (Scleratome) portion of the Meninx Primitiva. Makes the Dura Mater


2. Leptomeninges

Neural Crest portion of the Meninx Primitiva. Makes the Arachnoid Mater and the Pia Mater.