Covers how the cerebral cortex of the telencephalon is folded into sulci and gyri, and how these divide the hemisphere into five lobes plus the hidden insula. It works through the major separating sulci (central, lateral, parieto-occipital), then the sulci and gyri of the superolateral, inferior and medial surfaces lobe by lobe. A summary table of the lobes, a note on the insula's anterior and posterior parts with their functions, and several labelled pictures are included.
Topic 135 of 236 in the MU Pleven syllabus for Anatomy Bones and Muscles (Medicine, Year 2). The free AceMed note covers it in 5 sections, about 549 words (4 min of reading), with 10 flashcards.
In this note
SULCI and GYRI
Major sulci separating the lobes of the cerebral hemisphere:
Sulci & Gyri of the superolateral surface:
Sulci & Gyri of the inferior surface:
Sulci & gyri of medial surface:
SULCI and GYRI
The telencephalon (endbrain) gives rise to the cerebral hemisphere which consists of the superficial cerebral cortex convoluted to form gyri & sulci
sulci - depressions
gyri - elevated force
The sulci & gyri increase the surface area.
The sulci & gyri divide the hemisphere into 5 lobes:
Major sulci separating the lobes of the cerebral hemisphere:
1. Central sulcus: It start at the superomedial border just behind the midpoint between frontal & occipital poles
It descends on the lateral surface separating the frontal lobe from the parietal lobe
2. Lateral sulcus:
It has stem and 3 rami
It separates frontal and parietal lobes from the temporal lobe
3. Parieto-occipital sulcus:
It appears small in the supero-lateral surface while it is mainly present on the medial surface.
Separates the parietal and temporal lobes from the occipital lobe.
Sulci & Gyri of the superolateral surface:
1) Frontal lobe: It has:
Precentral sulcus: parallel to the central sulcus.
Precentral gyrus between central and precentral sulci.
From the precentral sulcus: 2 parallel sulci:
The superior and the inferior frontal sulci.
So 3 gyri are formed: superior, middle, and inferior frontal gyri.
Notice the inferior frontal gyrus which is divided by the stem and the rami of the lateral sulcus into 3 parts: orbital, triangular, and opercular.
2) Parietal lobe:
Postcentral sulcus: parallel to the central sulcus.
Postcentral gyrus: between central and postcentral sulci.
From the postcentral sulcus: one intraparietal sulcus.
Superior and inferior parietal lobules above and below the intraparietal sulcus respectively.
Notice the supramarginal gyrus "around the end of lateral sulcus" and the angular gyrus "around the end of superior temporal sulcus".
3) Temporal lobe:
2 sulci parallel to the lateral sulcus: superior and inferior temporal sulci.
So 3 gyri are formed: superior, middle, and inferior temporal gyri.
4) Occipital lobe:
It shows the end of the calcarine sulcus, with the surrounding lunate sulcus.
N.B: The insula:
Present in the floor of the lateral sulcus.
Surrounded by a circular sulcus except its apex "limen insulae"
Divided by central sulcus into large anterior and small posterior parts.
Anterior part having 3-4 short gyri.
Posterior part having a long gyrus.
Its function:
Anterior part: smell, taste, and autonomic areas.
Posterior part: 2nd somatosensory area.
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