Neurulation Flashcards
Overview of Neurulation (4)
1) Neuroectodermal tissues –> differentiate from ectoderm = neural plate + ectoderm on outsides
- border is formed to separate neural plate from ectoderm
2)Borders = close up to make a circle = neural crest
3)The closure of the tube leads to the neural crest disconnecting from the epidermis top= ectoderm midde=neuronal crest cells tube= neural tube Bottome= notochord
4)notochord at the bottom degenerates and is only found as the nucleus pulpous in the IVD
what do the neural crest cells go on to differentiate ?
peripheral nervous system
spinal ganglia etc
What are somites ?
longitudinal paired columns of PARA-AXIAL mesoderm
- form the cartilage , muscles of the back , cells that contribute to the CT of the dermis
Spina bifida occulta
- Incomplete fusion of the vertebrae, but with no herniation of the spinal cord
- May be visible only as a small tuft of hair overlying the site
Meningocele
- Incomplete fusion of the vertebrae, with herniation of a meningeal sac containing CSF
- Visible prominence at the site, but usually covered by skin
Myelomeningocele
- Incomplete fusion of the vertebrae with herniation of herniation of a meningeal sac containing CSF and spinal cord , prominent bump outwards
- Usually accompanied by other defects such as hydrocephaly or Chiari malformation
- Visible prominence at the site, with exposed meninges
how to treat neural tube defects?
folic acid 400mg/day
helps nucleic acid synthesis to form proper spinal chord
what cells are derived from the neuronal crest cells
name a few
Neural crest cells (NCCs) are a multipotent and migratory cell population in the developing embryo that contribute to the formation of a wide range of tissues.
- spinal route ganglia , nerve cells
- sheaths of peripheral nerves= schwann cells
- meninges of the Brain
- Melanocytes ( pigment of the skin )
- suprarenal glands = chromaffin cells ( adrenaline secretion)
- Adrenal medulla cells
describe the process of somitogenesis
- notochord and neuronal tube are surrounded by paraxial mesoderm
-differentiates and divides into paired somites
-42-44 Pairs of somites ,which each have:
Sclerotome –> bone
Myotome–> skeletal muscle
Dermatome–> connective tissue
derivatives of sclerotome , myotome and dermatome
scelerotome => bone
Myotome => muscle
dermatome => skin
ancephaly
Anencephaly is a serious birth defect in which a baby is born without parts of the brain and skull. I
encephalocele
A narrow channel that should close during early gestation to form the brain and spinal cord — does not close properly.
hydrocephalus
Hydrocephalus is a build-up of fluid in the brain. The excess fluid puts pressure on the brain, which can damage it.
list the secondary and primary vesicles , what do they become in the Brain
ProMesRho
Primary vesicles
1) Prosencephalon–> Telencephalon , diencephalon
2) Mesencephalon–>mesencephalon–>brain stem midbrain
3) Rhombencephalon–>metencephalon (brain stem , pons, cerebellum & Myelencephalon ( brain stem + medulla oblongata)
development flexures of the brain
formes 3 big bulges which will further differentiate into the 2ndary vesicles
1) prosencephalon
2) Mesencephalon ( doesn’t split into secondary vesicles )
3) Rhombencephalon
formation of the spinal chord :
spinal chord has 3 layers to begin with :
inner most layer: Ependymal layer which has stem cells to differentiate
middle mantle layer = nerve cell bodies
Outer Marginal layer= axons
development:
- Ears develop from centre ( dorsally , backwards )=> Alar plate =>posterior grey horn ( sensory )
- legs from the centre ( forward) => Basal plates => Ventral grey horn =>Motor neurones
what does the telencephalon form ?
cerebrum ( cerebral hemispheres )
what does the diencephalon form?
diencephalon ( thalamus, hypothalamus , epithalamus ) and retina
what does a) the mesencephalon form b)metencephalon form c) Myelencephalon (3)
mesencephalon –> mid brain
Metencephalon –> Brain stem Pons , Cerebellum
Myelencephalon–>Brain stem medulla Oblongata
How do the ventricles form in the brain ?
- Derivated from the dilation of the neural canal
-Dilation within the prosencephalon
( lateral , 3rd ventricle)
-Cavitation of the mesencephalon (cerebral aqueduct )
