The Neural Tube: From Neural Plate to Brain

The Neural Tube: From Neural Plate to Brain

The formation of the nervous system occurs very early in embryonic development.

Week 3:

• Day 18: The neural plate appears.

• End of week: The neural tube is formed from the neural groove, with the boundary between the future brain and spinal cord (2/3 head and 1/3 posterior groove) playing a major role.

Week 4:

• Day 26: The anterior neuropore closes.

• End of week: The posterior neuropore closes.

• 3 primary brain vesicles are formed: forebrain, midbrain, and hindbrain.

Differentiation of the neural tube:

• Neural crest: is the origin of the spinal ganglia, cranial nerve ganglia, autonomic ganglia, and chromaffin cells.

• Spinal cord: differentiates from the caudal part of the neural tube from the 4th body segment, with 3 main regions:

• Ventricular zone: unclear function.

• Intermediate zone: divides into 3 types of post-mitotic cells:

• Neuroblasts: precursors of neurons.

• Glioblasts: differentiate into astrocytes and oligodendrocytes, playing a supporting role for neurons.

• Post-mitotic epithelial cells: unclear function.

• Marginal zone: unclear function.

• Glial cells: originate from the mesenchyme of the neural tube.

Week 9:

• 5 secondary brain vesicles are formed: telencephalon, diencephalon, mesencephalon, metencephalon, and myelencephalon.

Division of the secondary brain vesicles:

• Forebrain: divides into the telencephalon and diencephalon.

• Midbrain: remains undivided, retaining the name midbrain.

• Hindbrain: divides into the metencephalon and myelencephalon.

Pituitary gland formation:

• Anterior lobe: originates from the primitive oral ectoderm.

• Posterior lobe: is a depression of the diencephalon.

Week 6:

• Corpus callosum: appears.

The nervous system is a complex and important system, formed from intricate changes during embryonic development.