Anatomy of the Brain: Major Regions

The human brain is a complex organ consisting of four main parts — the cerebrum, the cerebellum, the diencephalon, and the brainstem.

The cerebrum is the largest part of the brain, divided into left and right hemispheres separated by a deep medial longitudinal fissure.

The thin sheet of gray matter covering the cerebrum is called the cerebral cortex. It forms a series of elevations known as gyri and shallow grooves known as sulci.

To the posterior and inferior side of the cerebrum is the cerebellum. It has two interconnected hemispheres and is covered with gray matter called the cerebellar cortex.

The cerebral hemispheres surround the diencephalon. It houses three vital structures — the thalamus, the hypothalamus, and the epithalamus. 

The brainstem is the lowest part of the brain, including the midbrain, pons, and medulla oblongata.

The brain also has a protective covering of the meninges, made up of three layers — the dura mater, the arachnoid mater, and the pia mater.

The space between the arachnoid and pia mater is filled with cerebrospinal fluid that protects the brain from mechanical forces and supplies nutrients to the brain.