Lab 3 Brain Gross Anatomy

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.