What is gastrulation?
Formation of the Trilaminar Disc form the epiblast
Which embryological layer forms the Ns?
Ectoderm
How does CNS formation begin?
Ectoderm thickens just anterior to the primitive node (signals from primitive node trigger this) forming the Neural Plate
At the start of week 3
Then the edges thicken and move up to form neural folds
How is the neural tube formed?
Neural Folds migrate towards eachother, fusing at the midline. This starts at the middle (Around day 18) and works its way out to the ends.
It initially stays open at the ends (Neuropores) so the CNS is in contact with the amniotic fluid
When do the ends of the neural tube close?
Anterior (Cranial/Rostral) neuropore closes ~25 days
Posterior (Caudal) Neuropore closes ~27 days
When do the brain vesicles begin developing?
When the anterior neuropore closes around day 25
At which somite level does the brain form?
Above the 4th somite pair is brain and below that is Spinal cord & PNS
When do the various brain vesicles form?
3 primary vesicles form in week 4:
- Prosencephalon
- Mesencephalon
- Rhombencephalon
5 Secondary Vesicles form in week 5:
- Telencephalon
- Diencephalon
- Mesencephalon
- Metencephalon
- Myelencephalon
The brain has 3 flexures during embryology, what are they?
- Cephalic flexure (3rd week)
- Cervical Flexure (4th Week)
- Pontine Flexure (5th week)
Where is the cephalic flexure found?
Cephalic between the mesencephalon (midbrain) and rhombencephalon (Hindbrain)
Where is the cervical flexure found?
Between Hindbrain & Spinal Cord
Where is the pontine flexure found?
In the hindbrain between the metencephalon & Myelencephalon
What structures do each of the secondary vesicles become?
Telencephalon - Cerebrum, hippocampus & Basal Ganglia
Diencephalon - Thalmus, hypothalamus, pituitary & pineal glands
Mesencephalon - Midbrain
Metencephalon - Cerebellum, pons
Myelencephalon - Medulla
What ventricles form from which vesicles?
Telencephalon - Lateral
Diencephalon - 3rd
Mesencephalon - Cerebral Aqueduct
Rhombencephalon - 4th
When does CSF production begin?
5th week
Describe the inner surface of the neural tube?
Pseudostratified Neuroepithelial cells
How are neurons, glia, ependymal cells formed?
Neuroepithelial cells differentiate into neurons and Glial cells
(Except Microglia which from mesenchymal cells)
After they finish dividing the last neuroepithelial cells form ependymal cells
What are neural crest cells and what do they do?
Cells from the tip of the neural folds.
They migrate around the neural tube forming:
- Pigment cells
- DRG
- Autonomic ganglia
- Adrenal Medulla
Specifically how do neural crest cells form the DRG and associated spinal nerves?
The crest cell itself form the DRG and give off two processes:
- Peripheral Process extends into the body
- Central Process extends into the dorsal root & horn
How does the cauda equina form?
Basically during development the spinal cord reaches all the way to the coccyx, there the dura attaches and the sacral spinal nerves attach to their levels
Then the column and dura outgrow the cord.
Cord is elongated within the dural sac forming the cauda equina
This happens between month 3 and birth
