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Flashcards in Development Of The Nervous System Deck (34):

What is gastrulation?

When the bilaminar disc becomes the trilaminar disc Go from hypoblast and epiblast to endoderm, mesoderm and ectoderm


How is the neural tube formed?

Induction of the neural plate

Elevation of its lateral edges

The depressed mid region is the neural groove

Neural folds crash ally approach each other in the midline and fuse, producing the neural tube


What does the notochord serve as the basis of?

The midline, axial skeleton and neural tube


Where does fusion of the neural folds begin?

In the cervical region, then proceeds in both a cranial and caudal direction


What is neurulation?

The notochord-driven induction of ectoderm leading to formation of the neural plate and neural tube


When does neurulation begin?

Third week


When do the anterior and posterior neuropores close?

Anterior - day 25

Posterior - day 28


What are the different neural tube defects and how do they occur?

Spina bifida - failure of the neural tube to close caudally

Anencephaly - failure of the neural tube to close cranially


Where does spina bifida most commonly occur?

The lumbosacral region (but can occur anywhere along the length of the spinal cord)


What normally happens as a result of spina bifida?

Neurological deficits

Hydrocephalus nearly always

Not associated with mental retardation


What can happen if hydrocephalus is not treated in spina bifida?

Can cause cognitive delay


What are the different types of spina bifida?

Spina bifida aculta - no visible cyst, stays within the body column. Can be asymptomatic

Meningocoele - The arachnoid and meninges herniate out of the spinal cord

Myelomeningocoele - Both the neural tissue and meninges herniate out


What happens in anencephaly?

Failure of neural tube closure cranially 

Absence of cranial structures including the brain

Not compatible with life


What is rachischisis?

Failure of neural fold elevation leading to a splayed neural tube


How are neural tube defects diagnosed?

Raised maternal serum alpha-fetoprotein

Ultrasound scan


How to prevent neural tube defects?

Take folic acid for 3 months pre-conception and then for the first trimester


What is the cauda equina?

When the vertebral column grows faster than the spinal cord, the spinal roots need to elongate to exit at their intervertebral foramen, and so form the cauda equina beneath the spinal cord


Names for the forebrain, midbrain and hindbrain?

Forebrain = prosencephalon

Midbrain = mesencephalon

Hindbrain = rhombencephalon


How do the forebrain, midbrain and hindbrain develop?

During neural fold formation, three primary brain regions develop.

After neural tube closure in the fourth week, the dilations become the three primary brain vesicles


When do the secondary brain vesicles develop?

At 5 weeks of development 


What are the folds in the cranial neural tube?

Cervical flexure: spinal cord-hindbrain junction

Cephalic flexure: midbrain region 


Why do flexures develop in the neural tube?

Because there is not enough available space if the tube just grows linearly. 


Role of the ventricular system?

Cushion the brain and spinal cord within their bony cases


How is congenital hydrocephalus treated?

Use a shunt


What can cause hydrocephalus in a newborn?

Any blockage in the ventricular system

E.g. tumour, infection


What do the roof and floor plates of the neural tube do later on?

Regulate dorsal and ventral patterning 

Alar plate - sensory

Basal plate - motor


Where are neural crest cells found intitially and what do they do?

In the lateral border of the neuroectoderm tube

Become displaced and enter the mesoderm. Undergo epithelial mesenchymal transition


In the nervous system, name some things that are derived from neural crest cells

Cranial nerve ganglia

Dorsal root ganglia

Sympathetic/parasymapthetic ganglia

Schwann cells

Glial cells

Leptomeninges (arachnoid and pia)


What is derived from neural crest cells outside of the nervous system?

Connective tissue and bones of face and skull

Dermis of face and neck

C-cells of thyroid gland

Conotruncal septum of the heart


Adrenal medulla


What can cause defects in neural crest cell migration?

Environmental insult, especially alcohol



What is the syndrome seen when there is a defect in neural crest cell migration affecting multiple structures?

DiGeorge syndrome

  • Cardiac defects
  • Abnormal faces
  • Thymus aplasia
  • Cleft palate
  • Hypocalcaemia
  • 22 chromosome


What is the name of the syndrome when there is a defect in neural crest cell migration affecting one structure?

Hirschsprung's disease (aganglionic megacolon)


What are the layers of the neural tube?

The neuroepithelial layer made of neuroepithelial cells

The intermediate layer (mantle layer) made of neuroblasts

The marginal layer which has processes