Cerebral gyri

The raised areas or elevations found on the outer layer of the brain, known as the cerebral cortex, are called cerebral gyri.

The cerebral cortex consists of gray matter and encompasses the white matter tracts and inner deep subcortical nuclei. Because of its large surface area, the cerebral cortex is folded into various raised areas and grooves referred to as cerebral gyri and sulci. These folds allow the cerebral cortex to fit inside the limited space of the skull.

When looking at the outer or SUPEROLATERAL SIDE OF THE BRAIN, there are several important cerebral gyri. Specifically on the frontal cortex, we can identify the precentral gyrus, which extends downwards and forwards from upper margin of the cerebral hemisphere. This is where the primary motor region is located. In front of the precentral gyrus, there are three horizontally running gyri: including the superior, middle, and inferior frontal gyri. The inferior frontal gyrus is further divided into sub-parts by the rami or branches of the lateral sulcus. In the parietal lobe, the post-central gyrus runs behind and parallel to the precentral gyrus. Other notable gyri in the parietal lobe include the superior and inferior parietal lobules, located above and below the intra-parietal sulcus. The temporal lobe also contains the superior, middle and inferior temporal gyri.

On the MEDIAL OR INNER SIDE OF THE BRAIN, extensions of the pre and post-central gyri form a U-shaped paracentral lobule. In the central region, there is a C-shaped cingulate gyrus surrounding the corpus callosum. The cingulate gyrus is bounded superiorly by several gyri, including the medial frontal gyrus, the paracentral lobule, and the pre-cuneus. These gyri are all separated from the cingulate gyrus by the cingulate sulcus. Towards the posterior region, behind the parieto-occipital sulcus, the occipital lobe includes two main gyri: the cuneus and the lingual gyrus, above and below the calcarine sulcus.

On the UNDERSIDE OF THE CEREBRUM, the frontal lobe includes several orbital gyri and sulci, which are separated from the medial gyrus rectus (or straight gyrus) by an olfactory sulcus. Moving towards the back, the medial areas of the temporal and occipital lobes feature the parahippocampal gyrus, surrounded laterally by collateral and rhinal sulci. Further laterally, we can see the medial and then the lateral occipitotemporal gyri. The latter gyrus continues on the lateral side of the cerebrum as the inferior temporal gyrus.