Brain Anatomy Introduction
Brain Divisions

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.

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.

After this lab, you should be able to equate this three component classification scheme with the five brain divisions scheme. A graphic comparison is shown (right).

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.

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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