Recall that during embryonic development the brain is initially composed of three primary vesicles: Forebrain, Midbrain, and Hindbrain. These vesicles ultimately become five brain divisions: Telencephalon, Diencephalon, Mesencephalon (midbrain), Metencephalon, and Myelencephalon.
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The five brain divisions are convenient for regionally categorizing the locations of brain components. After this lab, you should be able to identify brain divisions present in a brain section or gross brain specimen that you are asked to inspect.
Embryonic Brain Division |
Derived Brain Structures |
Definitive Brain Cavities |
Associated Cranial Nerves |
FOREBRAIN Telencephalon Diencephalon |
Cerebrum Thalamus, Hypothalamus,... |
Lateral ventricles Third ventricle |
Olfactory (I) Optic (II) |
MIDBRAIN Mesencephalon |
Midbrain |
Mesencephalic aqueduct |
III & IV |
HINDBRAIN Metencephalon Myelencephalon |
Pons & Cerebellum Medulla oblongata |
Fourth ventricle Fourth ventricle |
Trigeminal (V) VI - XII |
Note: The terms forebrain and hindbrain have clinical significance with respect to localizing lesions diagnostically in patients.
Another way to subdivide the brain is: cerebrum, cerebellum, and brainstem. |
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The portion of brain remaining after the cerebrum and cerebellum are removed is referred to as the brainstem. Brainstem = diencephalon, mesencephalon, pons of the metencephalon, and myelencephalon. |
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The embryonic neural cavity develops into a brain ventricular system. Each of the five brain divisions houses a ventricle, except for the mesencephalon which contains the mesencephalic aqueduct. The cerebrum contains two ventricles, one in each hemisphere. |
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