Central Nervous System 3D stage 22 Movie

Embryology - 11 Dec 2023 Expand to Translate
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<html5media height="700" width="700">File:Stage22_CNS3d.mp4</html5media>

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Reconstruction of the central nervous system of the human embryo Carnegie stage 22. Note the size and general distribution of the brain and spinal cord.

Below the animation is a more complete description of each system.

Links: MP4 version | Quicktime version | Carnegie stage 22 | Neural System Development

Central Nervous System

During Week 5, as the neural tube continues to enlarge, the prosencephalon and rhombencephalon subdivide, while the mesencephalon expands. This gives rise to five secondary brain vesicles:

From the Prosencephalon:

Telencephlon – forms the cerebral hemispheres
Diencephlon – forms the thalamus and hypothalamus

Mesencephlon (doesn’t subdivide, expands) – forms the tectum and tegmentum

From the Rhombencephlon:

Metencephlon – forms the pons and the cerebellum
Myelencephlon – forms the medulla oblongata

In each of these areas, the central canal running through the CNS enlarges and forms the ventricular system within the adult brain.

As the tube grows in diameter, it also bends due to the rapid proliferation and ventral folding of the embryo. The resulting flexures that occur in the brain are called primary brain flexures. Three flexures occur:

cervical flexure occurs between the brain and the spinal cord.
cephalic flexure pushes the mesencephalon upwards
pontine flexure occurs in the opposite direction from the other two; it generates the 4th ventricle