Cerebrum (Main Sulci & gyri)
Cerebral hemisphere has 3 surfaces: Superolateral, medial and inferior surface. Inferior surface has 2 parts orbital (anterior, on frontal lobe)
and Tentorial (posterior, extending from temporal to occipital lobe). It has the 3 borders: Superomedial, inferomedial ( has 2 parts medial
orbital and medial occipital border) and inferolateral ( its anterior part is superciliary border)
Also consist of the following lobes: frontal lobe, occipital lobe, parietal lobe and temporal lobe. The parietal and temporal lobes are in-between
the frontal and occipital lobes, parietal lobe is superiorly then the temporal lobe is inferiorly.
Pre-occipital notch found about 5 cm anterior to occipital lobe. Grooves on surface of cerebral hemisphere are knowns as Sulci, the elevated
portions between sulci are called Gyri. There are many sulci and gyri on surface of cerebral hemisphere, the most important sulcus is the one
running downwards and forwards uninterrupted it’s called the Central sulcus it ends at upper part of posterior ramus of lateral sulcus (seen on
Superolateral and medial surface). Lateral sulcus has 3 parts/ rami coming from stem* , biggest of ramus going posteriorly is Posterior ramus of
lateral sulcus, the 2 others are short rami one going in front is Anterior horizontal ramus of lateral sulcus, & the last one is Anterior ascending
ramus of lateral ramus. Another sulcus which is on medial surface near occipital lobe is the Parieto-occipital sulcus (see on medial and
Superolateral surface), this sulcus along with another sulcus the Calcarine sulcus form a Y-shaped sulcus/sulci. There is an Imaginary line from
Parieto-occipital sulcus to Pre-occipital notch, behind this imaginary line is the occipital lobe. Another imaginary line running from end of
posterior ramus of lateral sulcus till it meets first imaginary line. Lobe above posterior ramus of lateral sulcus & in front of central sulcus is
Frontal lobe. Lobe between central sulcus and first imaginary line below limited by second imaginary line is the Parietal lobe. Lobe below
posterior ramus of lateral sulcus and second imaginary line until first imaginary line is the Temporal lobe.
Anterior to central sulcus is the Precentral gyrus also anterior to precentral gyrus is the precentral sulcus. Similarly posterior to central sulcus is
postcentral gyrus also posterior to it is the postcentral sulcus. I. Frontal lobe anterior to precentral sulcus there is superior frontal sulcus and
inferior frontal sulcus giving rise to superior frontal, middle frontal and inferior frontal gyrus. Part of inferior frontal gyrus between anterior
ascending & anterior horizontal rami of lateral sulcus is Pars triangularis, part behind anterior ascending ramus is Pars opercularis & part
inferior to anterior horizontal ramus is Pars orbitalis .On the parietal lobe there is a transverse sulcus which is called an Infraparietal lobe,
superior and inferior to it there is Superior parietal lobule and inferior parietal lobule respectively. Lunate sulcus near the occipital lobe
*(important). On the temporal lobe there is a superior temporal sulcus and the inferior temporal sulcus, giving rise to 3 gyri: superior temporal,
middle temporal & inferior temporal gyrus.
On Medial surface, Above the corpus callosum there is a callosal sulcus this sulcus lodges anterior cerebral artery and there is little gray matter
found in it which called induseum crestium, above this sulcus is cingulate gyrus above it its cingulate sulcus We find cuneus between Calcarine
and Parieto-occipital sulcus, below Calcarine sulcus is the lingual gyrus, & in front of Parieto-occipital sulcus is precuneus(seems to be
continuous with cingulate gyrus). Central sulcus extends to medial surface, the gyrus around Central sulcus on medial surface is paracentral
lobule (has 2 parts the anterior and posterior). Anterior to paracentral gyrus is medial frontal gyrus.
On inferior surface, we have olfactory sulcus which lodges olfactory tract and bulb. Medial to this sulcus is gyrus rectus. Orbital part is divided
into 4 by H shaped sulcus which is orbital sulcus, the 4 gyri are anterior, medial, lateral and posterior orbital gyrus. On Tentorial part, there is
collateral sulcus, lateral to this sulcus is occipito-temporal sulcus, dividing Tentorial part into 3 gyri medial to collateral sulcus is
parahippocampal gyrus( continuous posterior with lingual gyrus and anterior with uncus), between 2 sulci is medial occipito-temporal gyrus and
lateral to occipito-temporal sulcus is lateral occipito-temporal gyrus. Uncus is separated from medial occipito-temporal gyrus by rhinal sulcus.
Fig 1