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Note the following brain regions from caudal to cranial:

The Nervous System

Note the following brain regions from caudal to cranial:

• Medulla, which is the continuation of the spinal cord
• Pons, with the overlying cerebellum
• Midbrain
• Diencephalon
• Cerebral hemispheres

How Does the Brain Develop?

The Nervous System

The Nervous System

The Ventricular System (cavities filled with cerebrospinal fluid); note the following from cranial to caudal:

• Lateral ventricles in the cerebral hemispheres
• Third ventricle in the diencephalon
• Cerebral aqueduct in the midbrain
• Fourth ventricle in the pons and medulla

The Nervous System

The Nervous System

Formation of Brain Vesicles

Formation of the brain from the cranial neural tube occurs in steps:

• The first step is constriction of the tube, creating three primary vesicles, the forebrain/prosencephalon, midbrain/mesencephalon, and hindbrain/rhombencephalon.
• The next step is for two of these vesicles to further constrict, creating a total of five secondary vesicles. These five secondary vesicles, the telencephalon, diencephalon, mesencephalon, metencephalon, and myelencephalon, give rise to all the named regions of the fully formed brain. Note the additional constriction in the telencephalon midline: it creates the two cerebral hemispheres.

The Nervous System

The Nervous System

The Nervous System

The Nervous System

Formation of the Brainstem

The Nervous System

What are the fates of the alar and basal plates in the brainstem?