Development of the central nervous system

In this note, we are going to discuss the embryological development of the central nervous system.

Germ layers

We know that the embryo has three germ layers: ectoderm, mesoderm, and endoderm, each of which then gives rise to certain tissues.

The nervous tissue develops from the ectoderm, the outer layer of the embryo.

Neurulation

At first, there is a neural plate,

which then gets longer and gradually deepens. At some stage, it has the form of two neural folds, with a neural groove between them.

Eventually, the neural groove completely fuses into the neural tube,

in the center of which is located the neural canal.

And the cells of the neural folds form a so-called neural crest above the tube and on either side of it.

All these structures are sometimes referred to as “neuroectoderm”. The whole process of their development is called neurulation, and it is completed by the 4th week of embryonic development.

Brain vesicles (1° and 2°)

And then the most interesting and, perhaps, the most important process begins. From the cranial end, the neural tube begins to dilate, and it dilates in the form of the three primary brain vesicles. These vesicles are called:

Rhombencephalon (or hindbrain)

Mesencephalon (or midbrain)

Prosencephalon (or forebrain)

Then the three primary brain vesicles give rise to five secondary brain vesicles:

Myelencephalon

Metencephalon

Mesencephalon

Diencephalon

Telencephalon

As you can see, each secondary brain vesicle eventually gives rise to a specific division of the brain, each of which has its own cavity or ventricle.

Well, and the caudal end of the neural tube lengthens and narrows to form the spinal cord. And, finally, the cells of the neural crest give rise to the structures of the peripheral nervous system.

Golosary