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Flashcards in Development of the nervous system Deck (16):
1

Neurulation

After gastrulation
Formation/closure of neural tube
During 3rd week of intrauterine life
Induction of surface ectoderm by underlying notochord
Midline cells in region cranial to primitive node begin to proliferate
Formation of thickened epithelium, which eventually folds

2

Closure of neural tube

Closure begins in cervical region then proceeds upwards (cranial) and downwards (caudal) in zip-like fashion
current evidence: multiple closure sites
Last regions:
- anterior neuropore (25th day post-fertilization)
- posterior neuropore (27th day post-fertilization)
Neural canala: central canal of spinal cord and ventricles of the brain

3

Layers of neural cells

Neuroepithelial cells --> neuroblasts --> neurons
Pseudostratified epithelium
Neuroepithelial cells also form neural glia --> astrocytes, oligodendrocytes
Ventricular layer: little nuclei, next to lumen, become ependyma
Intermediate (mantle) layer: thickest, become gray matter of spinal cord and neurons, lots of nuclei
Marginal layer: axons of nerve cells, white matter of spinal cord

4

Neural crest cells

Formed at crest of neural folds
Ectodermal in origin
Change appearance from ectodermal (flat) to mesenchymal (spindle-shaped)
- detach from ectoderm and migrate extensively
Pluripotent
Function severely damaged by maternal alcohol abuse

5

FASD

most common avoidable mental retardation
low birth weight
delayed psychomotor skills
facial abnormalities: small eyes, decreased nasal bridge, very thin upper lip
Delayed psychological manifestations

6

Types of spina bifida

Occulta (unfused vertebral arch, tuft of hair above)
Meningocele (Large CSF-filled subarachnoid space)
Meningomyelocele (Spinal cord displaced outside)
Myeloschisis (open spinal cord)

7

Spina bifida etiology

multifactorial
Hyperthemia
Valproic acid
excessive intake of vitamin A

8

Spina bifida Dx

Ultrasound (8-10 weeks)
AFP in maternal serum and amniotic fluid

9

Spina bifida prevention

0.4 mg folic acid daily before and during pregnancy

10

Development of the brain

Closure of anterior neuropore --> 3 dilatations at the cranial end of neural tube
- primary brain vesicles: forebrain, midbrain, hindbrain
Vesicles further divide (except for midbrain) to produce five secondary brain vesicles

11

Telencephalon

cerebral hemisphereslateral ventricle

12

Diencephalon

hypothalamus, part of pituitary
3rd ventricle

13

Mesencephalon

Midbrain
cerebral peduncles
superior and inferior colliculi
cerebral aqueduct

14

Metencephalon

pons and cerebellum
4th ventricle

15

Myelencephalon

Medulla oblongata
4th ventricle

16

Flexures of the brain

grows rapidly, bends ventrally --> flexure formation
Result in analteration to basic arrangement of gray and white matter
Flexure in pontine region --> thinning of dorsal wall (roof) of
Cervical, midbrain (cephalic) and pontine flexures