Transcript Topography of the Cerebral Hemispheres

Topography of the Cerebral
Hemispheres
Surface structures
• 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.
Major sulci and fissures
• 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 lobe
• 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
• superior and inferior temporal sulci divides
the temporal lobe into:
– superior temporal gyrus
– middle temporal gyrus
– inferior temporal gyrus
Occipital lobe
• Primary visual center
Insular lobe
• 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
• Corpus callosum
– splenium: posterior enlarged portion
– Genu: anterior portion
– Rostrum: thinning out of Genu
Medial 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
Medial surfaces
• Cingulate sulcus gives off paracentral sulcus
then terminates into marginal and subparietal
sulcus
• 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
Inferior surface
• orbital gyri: lateral to the olfactory sulcus
• uncus: above the parahippocampal gyrus
• isthmus: underneath the splenium of
corpus callosum, connects cingulate and
parahippocampal gyri
Cerebellum
• The cerebellum consists of cortex of gray
matter (folia), a medullary center of white
matter, and four pairs of central nuclei
• Primary fissure separates anterior lobe
and posterior lobe
Cerebellum
• The region around the midline is called
vermis (superior and inferior vermis) and
the reminder is referred as hemispheres.
• Three main lobes
– Flocculonodular lobe: includes nodule and
Flocculus located in between anterior lobe
and posterior lobe
– Anterior lobe
– Posterior lobe