The two cerebral hemispheres are divided in the midsagittal plane by the interhemispheric fissure. Together they fill most of the intra-cranial cavity.
The medial surface of each cerebral hemisphere is flat, the inferior surface is irregular and even slightly concave anteriorly, while the lateral surface is convex. They are all lined by cerebral cortex.
The surface of the cerebral hemisphere is divided by grooves, called sulci, into ridges called gyri.
Each cerebral hemisphere is divided into four lobes of unequal size :
- frontal lobe: 41% of total neocortical volume
- temporal lobe: 22%
- parietal lobe: 19%
- occipital lobe: 18%