Neurulation Flashcards
(21 cards)
What is neurulation?
The formation of the vertebrate nervous system in embryos.
What structure induces the formation of the CNS?
The notochord.
How does neurulation occur?
Notochord induces the formation of the CNS by signalling ectoderm above it to form a thick neural plate, the neuroectoderm.
Where does the notochord arise from?
The mesoderm.
Where does the neural tube arise from?
The ectoderm.
How does the notochord develop?
Mesodermal cells migrate cranially in the midline of the mesodermal layer, forming the rod-like notochord.
How does the neural tube develop?
Neural plate folds in on itself, with the neural folds fusing together to form a neural tube. The neural tube then separated from the surface ectoderm. Cells at the crest of each fold disperse in various directions through the mesenchyme.
What are neural crest cells?
Pluripotent cells which give rise to various nervous structures in the embryo (e.g. Spinal ganglia, melanocytes, meninges of brain, etc.).
When do the neuropores close?
Anterior neuropore = day 24.
Posterior neuropore = day 26.
What is the adult derivative of the notochord?
The nucleus pulposus of the intervertebral discs.
What are the primary rain vesicles?
The prosencephalon (forebrain), mesencephalon (midbrain) and rhombencephalon (hindbrain).
What does the mantle layer of the neural tube give rise to?
The cell bodies of motor neurones (gray matter).
What does the marginal layer of the neural tube give rise to?
Axons of motor neurones (white matter).
What can cause congenital abnormalities?
Teratogenic drugs, as they effect the neuroectoderm.
What causes spina bifida?
Failure of the vertebral arches to fuse.
What is the difference between spina bifida occulta and cystica?
Occulta is the mildest form, vertebrae fail to fuse dorsally but often the split is very small so no herniation.
Cystica can have protrusion of meninges and neural tissue, much more serious.
What is encephaloceles?
Sac-like protrusion of brain and meninges through opening in cranial vault.
What is anencephaly?
Failure of anterior part of neural tube to close.
What can prevent congenital abnormalities?
Folic acid supplements for first three months of pregnancy.
How do donkeys develop?
Paraxial mesoderm forms at either side of the notochord - this differentiates into paired cuboidal bodies, the somites.
How do somites differentiate?
Sclerotome - forms bone.
Myotome - forms muscle.
Dermatome - forms connective tissue.
