Neurulation

Question 1

Overview of Neurulation (4)

Answer 1

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

Question 2

what do the neural crest cells go on to differentiate ?

Answer 2

peripheral nervous system

spinal ganglia etc

Question 3

What are somites ?

Answer 3

longitudinal paired columns of PARA-AXIAL mesoderm

- form the cartilage , muscles of the back , cells that contribute to the CT of the dermis

Question 4

Spina bifida occulta

Answer 4

• 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

Question 5

Meningocele

Answer 5

• Incomplete fusion of the vertebrae, with herniation of a meningeal sac containing CSF
• Visible prominence at the site, but usually covered by skin

Question 6

Myelomeningocele

Answer 6

• 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

Question 7

how to treat neural tube defects?

Answer 7

folic acid 400mg/day

helps nucleic acid synthesis to form proper spinal chord

Question 8

what cells are derived from the neuronal crest cells

name a few

Answer 8

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

Question 9

describe the process of somitogenesis

Answer 9

• 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

Question 10

derivatives of sclerotome , myotome and dermatome

Answer 10

scelerotome => bone
Myotome => muscle
dermatome => skin

Question 11

ancephaly

Answer 11

Anencephaly is a serious birth defect in which a baby is born without parts of the brain and skull. I

Question 12

encephalocele

Answer 12

A narrow channel that should close during early gestation to form the brain and spinal cord — does not close properly.

Question 13

hydrocephalus

Answer 13

Hydrocephalus is a build-up of fluid in the brain. The excess fluid puts pressure on the brain, which can damage it.

Question 14

list the secondary and primary vesicles , what do they become in the Brain
ProMesRho

Answer 14

Primary vesicles

1) Prosencephalon–> Telencephalon , diencephalon
2) Mesencephalon–>mesencephalon–>brain stem midbrain
3) Rhombencephalon–>metencephalon (brain stem , pons, cerebellum & Myelencephalon ( brain stem + medulla oblongata)

Question 15

development flexures of the brain

Answer 15

formes 3 big bulges which will further differentiate into the 2ndary vesicles

1) prosencephalon
2) Mesencephalon ( doesn’t split into secondary vesicles )
3) Rhombencephalon

Question 16

formation of the spinal chord :

Answer 16

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

Question 17

what does the telencephalon form ?

Answer 17

cerebrum ( cerebral hemispheres )

Question 18

what does the diencephalon form?

Answer 18

diencephalon ( thalamus, hypothalamus , epithalamus ) and retina

Question 19

what does 
a) the mesencephalon form 
b)metencephalon form 
c) Myelencephalon 
(3)

Answer 19

mesencephalon –> mid brain
Metencephalon –> Brain stem Pons , Cerebellum
Myelencephalon–>Brain stem medulla Oblongata

Question 20

How do the ventricles form in the brain ?

Answer 20

• Derivated from the dilation of the neural canal
  -Dilation within the prosencephalon
  ( lateral , 3rd ventricle)
  -Cavitation of the mesencephalon (cerebral aqueduct )