Download Topography of the cerebral hemispheres The surface of the brain

Topography of the cerebral hemispheres
The surface of the brain has complicated folding which substantially increases the surface area of the brain.
Gyrus (Gyri, pl) Folds or convulsions
Sulcus (Sulci, pl) Intervening grooves
Fissure: cleft separates large components of the brain. May be used interchangeably with sulcus
Major sulci and fissures
1. Lateral sulcus separates frontal and temporal lobes starts from inferior surface of the hemisphere, stem
(beginning segment) of the sulcus extends laterally and divides into three rami on reaching the lateral surface,
anterior, ascending, and posterior ramus
2. Central sulcus separates frontal and parietal lobes. Primary motor area is in front of it and somatosensory
area is right behind.
3. Calcarine sulcus on the medial surface of the hemisphere starts posterior to the corpus callosum, arches
down to the occipital pole
4. Parieto-occipital sulcus separates occipital and parietal lobes extends from calcarine sulcus to the superior
border of the hemisphere
Fissure
1. Longitudinal cerebral fissure separates two hemispheres falx cerebri extends into the fissure
2. Transverse cerebral fissure separates cerebral hemisphere with cerebellum. tentorium cerebeli extends into
the fissure. The anterior part of the fissure separates cerebral hemisphere with midbrain and diencephalon
Lobes:
Frontal lobe: in front of central sulcus and above lateral sulcus, line from central sulcus down to corpus
collosum
Parietal lobes: behind central sulcus and above lateral sulcus. A line between parieto-occipital sulcus and
preoccipital notch and middle of the line above to the lateral sulcus (See Picture 13-1 on P261)
Temporal lobes: lateral sulcus and line described above, a line from anterior end of calcarine sulcus and
preoccipital notch (see Pic 13-2 on P 262)
Occipital lobe: medial surface of the hemisphere, separated from temporal lobe.
Insula: bottom of lateral sulcus.
other gyri and sulci on frontal lobes
precentral sulcus: parallel to central sulcus (see pictures in the book)
precentral gyrus: between central sulcus and precentral sulcus, primary motor area
parallel with longitudinal fissure, two more sulci on the frontal lobe, superior frontal sulcus and inferior
frontal sulcus
between longitudinal fissure and superior frontal sulcus: superior frontal gyrus
between superior frontal sulcus and inferior frontal sulcus: middle frontal gyrus
between inferior frontal sulcus and lateral sulcus: inferior frontal gyrus
inferior frontal gyrus is further divided into three parts by the anterior and ascending rami of the lateral sulcus
1). opercular portion: enclosed by precentral sulcus, inferior frontal sulcus, and ascending ramus
2). triangular portion: enclosed by ascending ramus, anterior ramus, and inferior frontal sulcus
3). orbital portion: lateral sulcus, anterior ramus, and inferior frontal sulcus
Parietal lobes: central and lateral sulcus on the lateral surface line between parieto-occipital sulcus and the
preoccipital notch, and middle of the line above to lateral sulcus
postcentral sulcus: parallel to the central sulcus sandwiched postcentral gyrus (somatosensory cenetr) with
central sulcus
Intraparietal sulcus: extends posteriorly from the postcentral sulcus divide parietal lobe not occupied by
postcentral gyrus into superior parietal lobules and inferior parietal lobules
inferior parietal lobules can further be divided into:
supramarginal gyrus: surrounds the upturned ends of lateral sulcus
angular gyrus: surrounds superior temporal sulcus
Temporal lobes: border see Fig 13-1 superior and inferior temporal sulci divides the temporal lobe into:
superior temporal gyrus middle temporal gyrus inferior temporal gyrus
Occipital lobe:
Corpus callosum medial view: splenium: posterior enlarged portion Genu: anterior portion rostrum: thinning
out
Insular lobe covered by frontal, parietal, and temporal opercula
outlined by circular sulcus, central sulcus of insula divides insula into several short gyri, one or two long gyri
and limen insulae (over the stem of lateral sulcus)
Medial and inferior surfaces
cingulate gyrus: above the corpus collosum, starts beneath the genu of the corpus collasum goes back to
splenium.
Sulcus of the callosum (callosal sulcus)
Cingulate sulcus: above the callosal sulcus
Medial frontal Gyrus: separates from cingulate gyrus by cingulate sulcus
Cingulate sulcus gives off paracentral sulcus then terminates into marginal and subparietal sulci
Paracentral lobule: bounded by paracentral and marginal sulci
Precuneus: area above subparietal sulcus
Cuneus: bounded by parieto-occipital and calcarine sulci
Under the corpus collosum, convolution extends from occipital pole
Inferior surface:
lingual gyrus: between collateral sulcus and calcarine sulcus. The anterior part is called parahippocampal
gyrus, which lateral to uncus.
Rhinal sulcus, located at the lateral edge of the parahipocampal gyrus, defines the entorhinal area, which
belongs to both limbic system and olfactory system.
occipitotemporal sulcus: intervenes the medial occipitotemporal gyrus and lateral occipitotemporal
gyrus
Orbital surface of the frontal lobe: gyrus rectus: medial to the olfactory sulcus
orbital gyri: lateral to the olfactory sulcus
uncus: above the parahippocampal gyrus
isthmus: underneath the splenium of corpus callosum, connects cingulate and parahippocampal gyri