Brain

1. Dr. Komal Parmar
Gyri,
Sulci
and
Cerebral
Lobes

2. • The cerebral hemispheres are separated
by a deep median cleft, the great
longitudinal fissure, which contains a
crescent-shaped fold of the dura mater,
the falx cerebri.
• Each cerebral hemisphere may be
considered to have superolateral,
medial and inferior (basal) surfaces or
aspects.
• The tentorial part lies in the middle
cranial fossa; posteriorly it lies above
the tentorium cerebelli, which separates
it from the superior surface of the
cerebellum.

3. • Each hemisphere consists of an
external highly-convoluted
cortex, beneath which lies an
extensive internal mass of white
matter that partly encloses the
basal ganglia.
• Each hemisphere also contains a
lateral ventricle that is
continuous with the third
ventricle through the
interventricular foramen. The
two hemispheres are linked by
the commissural fibres of the
corpus callosum.

5. • The area of the adult cerebral cortex is approximately 2200 cm²: its
convoluted form increases the cortical volume to three times greater
than it would be if the surface were smooth.

6. Sulci and
related
Gyri
- The very obvious
and easily
identifiable ones

7. Sulci Types

8. Lateral Sulcus
• The lateral fissure is a deep cleft on the
lateral and inferior surfaces.
• It separates the frontal and parietal lobes
above from the temporal lobe below and
accommodates the middle cerebral vessels.
• It commences inferiorly at the anterior
perforated substance, extending laterally
between the orbital surface of the frontal
lobe and the anterior pole of the temporal
lobe and accommodating the sphenoparietal
venous sinus.

12. Central Sulcus of Rolando
• The central sulcus is the boundary between
the frontal and parietal lobes and
demarcates the primary motor and
somatosensory areas of the cortex, located
in the precentral and postcentral gyri,
respectively.
• It starts in or near the superomedial border
of the hemisphere, a little behind the
midpoint between the frontal and occipital
poles.
• It runs sinuously downwards and forwards
to end a little above the posterior ramus of
the lateral sulcus.

17. • The superior frontal gyrus,
above the superior frontal
sulcus, is continuous over
the superomedial margin
with the medial frontal
gyrus and may be
incompletely divided.
• The middle frontal gyrus
lies between the superior
and inferior frontal sulci.
• The inferior frontal gyrus
lies below the inferior
frontal sulcus which is
invaded by the ascending
ramus of the lateral fissure.
• In the left hemisphere, the
cortical areas around this
ramus make up the motor
speech area (Broca’s area;
areas 44 and 45).
Frontal Gyri and Sulci

18. Cingulate Sulcus
• starts below the rostrum and passes first forwards, then up and finally
backwards, conforming to the callosal curvature.
• Its posterior end turns up to the superomedial margin of the hemisphere
approximately 4 cm behind its midpoint, and is posterior to the upper
end of the central sulcus.
•
• Divides the anterior region of medial surface into
outer and inner zone.
• The outer zone, except for its posterior extremity,
is part of the frontal lobe, and is subdivided into
anterior and posterior areas by a short sulcus,
which ascends from the cingulate sulcus above the
midpoint of the corpus callosum.
• The larger anterior area is the medial frontal gyrus;
the posterior is the paracentral lobule.
• The superior end of the central sulcus usually
invades the paracentral lobule posteriorly.

19. • The zone under the cingulate sulcus is the cingulate gyrus. Starting
below the rostrum, this gyrus follows the callosal curve, separated by
the callosal sulcus.
• It continues round the splenium to the inferior surface, and then into
the parahippocampal gyrus, through the narrow isthmus.

20. • The parietooccipital and the
calcarine sulci
• These two deep sulci converge
anteriorly to meet a little posterior to
the splenium.
• The parieto-occipital sulcus marks the
boundary between parietal and occipital
lobes.
• It starts on the superomedial margin of
the hemisphere approximately 5 cm
anterior to the occipital pole, sloping
down and slightly forwards to the
calcarine sulcus.
• The calcarine sulcus starts near the
occipital pole.
• Though usually restricted to the medial
surface, its posterior end may reach the
lateral surface.
• Directed anteriorly, it joins the
parietooccipital sulcus at an acute angle
behind the splenium.

21. • Continuing forwards, the calcarine sulcus crosses the inferomedial margin of
the hemisphere, and forms the inferior boundary of the isthmus, which
connects the cingulate with the parahippocampal gyrus.
• The visual cortex lies above and below the posterior part of the calcarine
sulcus, behind the junction with the parieto-occipital.
• The calcarine sulcus is deep and produces an elevation, the calcar avis, in the
wall of the posterior horn of the lateral ventricle.

23. Precuneus and Cuneus
• The area posterior to the upturned end of
the cingulate sulcus, and anterior to the
parieto-occipital sulcus, is the precuneus.
• It forms the medial surface of the parietal
lobe with the part of the paracentral lobule
behind the central sulcus.
• The medial surface of the occipital lobe is
formed by the cuneus, a wedge of cortex
bounded in front by the parieto-occipital
sulcus, below by the calcarine sulcus, and
above by the superomedial margin.

24. Orbital Surface
• On the orbital part of the basal
surface, a rostrocaudal olfactory
sulcus traverses it near its medial
margin, overlapped by the
olfactory bulb and tract.
• The medial strip thus demarked is
the gyrus rectus.
• The rest of this surface bears
irregular orbital sulci, generally H-
shaped, which divide it into the
anterior, medial, posterior and
lateral orbital gyri

26. Collateral sulcus
• The collateral sulcus starts near the
occipital pole, and extends
anteriorly and parallel to the
calcarine sulcus, separated from it
by the lingual gyrus.
• The lingual gyrus, between the
calcarine and collateral sulci, passes
into the parahippocampal gyrus,
which begins at the isthmus where
it is continuous with the cingulate
gyrus.

29. • Anteriorly, the parahippocampal
gyrus continues into the hook-
shaped uncus, which lies lateral to
the midbrain and posterolateral to
the anterior perforated substance.
• The uncus is part of the piriform
cortex of the olfactory system,
phylogenetically one of the oldest
parts of the cortex, and is
separated from the temporal pole
by the rhinal sulcus (fissure) which
marks the lateral limit of the
entorhinal cortex (area)

33. Occipitotemporal sulcus
• The occipitotemporal sulcus is parallel
and lateral to the collateral sulcus,
does not usually reach the occipital
pole, and is frequently divided.
• The medial occipitotemporal gyrus
extends from the occipital to the
temporal pole and is limited medially
by the collateral and rhinal sulci and
laterally by the occipitotemporal
sulcus.
• The lateral occipitotemporal gyrus is
continuous, round the inferolateral
margin of the hemisphere, with the
inferior temporal gyrus.

35. Lobes and
Sulci &
related Gyri,
again

36. Lobes
•Frontal
•Parietal
•Temporal
•Insular
•Occipital
•Limbic

37. 1. Frontal Lobe
• The frontal lobe is the rostral region of the
hemisphere, anterior to the central sulcus and
above the lateral fissure.
• The precentral gyrus runs parallel to the
central sulcus on the superolateral surface and
extends onto the medial surface, and is limited
anteriorly by the precentral sulcus.
• The area of the frontal lobe anterior to the
precentral sulcus is divided into the superior,
middle and inferior frontal gyri.
• The medial surface extends from the frontal
pole to the paracentral lobule and consists of
the medial side of superior frontal gyrus
(medial frontal gyrus) and the anterior half of
cingulate gyrus.
• The frontal pole lies in front of these gyri. The
ventral surface of the frontal lobe, the
orbitofrontal cortex, overlies the bony orbit.

39. Orbital Surface
• On the orbital part of the basal
surface, a rostrocaudal olfactory
sulcus traverses it near its medial
margin, overlapped by the
olfactory bulb and tract.
• The medial strip thus demarked is
the gyrus rectus.
• The rest of this surface bears
irregular orbital sulci, generally H-
shaped, which divide it into the
anterior, medial, posterior and
lateral orbital gyri

40. • straight gyrus,(or gyrus
rectus) and is continuous
with the superior frontal
gyrus on the medial
surface.

41. Frontal Pole
• It does not have easily
defined boundaries,
but is roughly
equivalent to
the frontopolar
cortex, which in turn
is continuous with the
anterior margins of
the gyri of the lateral,
medial and inferior
surfaces of the frontal
lobe.
• Prefrontal Cortex

42. Inferior Frontal Gyrus
• The inferior frontal gyrus is highly
convoluted and has
three cytoarchitecturally diverse
regions.
• The three subdivisions are an
opercular part, a triangular part,
and an orbital part. These divisions
are marked by two rami arising
from the lateral sulcus.The
ascending ramus separates the
opercular and triangular
parts.[4] The anterior (horizontal)
ramus separates the triangular and
orbital parts.

44. Cingulate Cortex

45. 2. Parietal Lobe

46. Boundaries
• On Superolateral Surface-
• Anteriorly- Central Sulcus
• Posteriorly and Inferiorly-
• Imaginary Line 1- Indentation of
Parieto-occipital Sulcus to
Preoccipital Notch
• Imaginary Line 2- Extension of
Sylvian Fissure
• On Medial Surface-
• Anteriorly- Central Sulcus
• Posteriorly- Parieto-occipital
Sulcus

48. • The lateral aspect of the parietal lobe is
divided into three areas by postcentral
and intraparietal sulci.
• The postcentral sulcus, often divided
into upper and lower parts, is posterior
and parallel to the central sulcus.
• Inferiorly, it ends above the posterior
ramus of the lateral fissure. The
postcentral gyrus or primary
somatosensory cortex lies between the
central and postcentral sulci.
• Posterior to the postcentral sulcus there
is a large area, subdivided by the
intraparietal sulcus.
• It usually starts in the postcentral sulcus
near its midpoint and extends
posteroinferiorly across the parietal
lobe, dividing the latter into superior
and inferior parietal lobules.

49. • The superior parietal lobule lies between the
superomedial margin of the hemisphere and the
intraparietal sulcus, is continuous anteriorly with the
postcentral gyrus round the upper end of the
postcentral sulcus.
• The inferior parietal lobule, below the intraparietal
sulcus and behind the lower part of the postcentral
sulcus, is divided into three.
• The anterior part is the supramarginal gyrus, which
arches over the upturned end of the lateral fissure.
It is continuous anteriorly with the lower part of the
postcentral gyrus and posteroinferiorly with the
superior temporal gyrus.
• The middle part of the inferior parietal lobule, called
the angular gyrus, arches over the end of the
superior temporal sulcus and is continuous
posteroinferiorly with the middle temporal gyrus.
• The posterior part of the inferior parietal lobule
arches over the upturned end of the inferior
temporal sulcus on to the occipital lobe

52. 3. TEMPORAL LOBE
• The temporal lobe is inferior to
the lateral fissure.
• It is limited behind by an arbitrary
line from the preoccipital incisure
to the parieto-occipital sulcus
(Line No. 1) which meets the
superomedial margin of the
hemisphere approximately 5 cm
from the occipital pole.
• Its lateral surface is divided into
three parallel gyri by the superior
and inferior temporal sulci.

53. • The superior temporal sulcus begins
near the temporal pole and slopes
slightly up and backwards parallel
to the posterior ramus of the lateral
sulcus. Its end curves up into the
parietal lobe.
• The inferior temporal sulcus is
subjacent and parallel to the
superior and is often broken into
two or three short sulci. Its
posterior end also ascends into the
parietal lobe, posterior and parallel
to the upturned end of the superior
sulcus.
Temporal Sulci- Lateral Surfcae

54. Temporal Gyri- Lateral Surface
• The three parallel
gyri on the lateral
surface of the
temporal lobe are
the superior;
middle; and
inferior temporal
gyri.
• The temporal pole
lies in front of the
termination of
these gyri.

55. • Along its superior margin
the superior temporal
gyrus is continuous with
gyri in the floor of the
posterior ramus of the
lateral sulcus.
• These vary in number, and
extend obliquely
anterolaterally from the
circular sulcus around the
insula as the transverse
temporal gyri of Heschl
• The anterior transverse
temporal gyrus and
adjoining part of the
superior temporal gyrus
are auditory in function

57. Medial Side of the
Temporal Lobe
• The cortex of the medial
temporal lobe includes
major subdivisions of the
limbic system, such as the
hippocampus and entorhinal
cortex.
• Areas of neocortex adjacent
to these limbic regions are
grouped together as medial
temporal association cortex.

58. Lingual Gyrus
• The lingual gyrus aka medial
occipitotemporal gyrus of
the occipital lobe lies between
the calcarine sulcus and the
posterior part of the collateral
sulcus; behind, it reaches the
occipital pole; in front, it is
continued on to the tentorial
surface of the temporal lobe,
and joins the parahippocampal
gyrus

59. 4. INSULA
• The insula lies deep in the fl oor of the lateral fi
ssure, almost surrounded by a circular sulcus, and
overlapped by adjacent cortical areas, the
opercula.
• The frontal operculum is between the anterior and
ascending rami of the lateral fissure, forming a
triangular division of the inferior frontal gyrus.
• The frontoparietal operculum, between ascending
and posterior rami of the lateral fi ssure, consists of
the posterior part of the inferior frontal gyrus, the
lower ends of the precentral and postcentral gyri,
and the lower end of the anterior part of the
inferior parietal lobule.
• The temporal operculum, below the posterior
ramus of the lateral fissure, is formed by superior
temporal and transverse temporal gyri.
• Anteriorly, the inferior region of the insula adjoins
the orbital part of the inferior frontal gyrus.

60. Opercula
• The frontal operculum is between the
anterior and ascending rami of the
lateral fissure, forming a triangular
division of the inferior frontal gyrus.
• The frontoparietal operculum,
between ascending and posterior
rami of the lateral fissure, consists of
the posterior part of the inferior
frontal gyrus, the lower ends of the
precentral and postcentral gyri, and
the lower end of the anterior part of
the inferior parietal lobule.
• The temporal operculum, below the
posterior ramus of the lateral fissure,
is formed by superior temporal and
transverse temporal gyri.
• Anteriorly, the inferior region of the
insula adjoins the orbital part of the
inferior frontal gyrus.

61. • When the opercula are removed, the
insula appears as a pyramidal area, its
apex beneath and near the anterior
perforated substance, where the circular
sulcus is deficient.
• The medial part of the apex is termed
the limen insulae (gyrus ambiens).
• A central insular sulcus, which slants
posterosuperiorly from the apex, divides
the insular surface into a large anterior
and a small posterior part.
• The anterior part is divided by shallow
sulci into three or four short gyri,
whereas the posterior part is one long
gyrus, often divided at its upper end.
• The cortex of the insula is continuous
with that of its opercula in the circular
sulcus. The insula is approximately
coextensive with the subjacent claustrum
and putamen.

65. • The claustrum is a thin sheet of
grey matter lying deep to the
insula.
• It is approximately coextensive with
the insula, from which it is
separated by the extreme capsule.
• Medially, the claustrum is
separated from the putamen by the
external capsule.

66. 5. OCCIPITAL LOBE
• The occipital lobe lies behind an arbitrary line joining the preoccipital incisure and
the parieto-occipital sulcus.
• On Lateral Side-

68. Lunate Sulcus
• In brain anatomy, the lunate
sulcus or simian sulcus also
known as the sulcus lunatus is
a fissure in the occipital
lobe variably found
in humans and more often
larger when present
in apes and monkeys.

69. Lateral Occipital Sulcus
• In the occipital lobe, the lateral
occipital sulcus, where present,
divides the lateral, or middle
occipital gyrus into a superior
and an inferior part, which are
then continuous in front with
the parietal and temporal lobes.
• The anterior portion is often
incomplete, but in some
individuals it may encounter
the superior temporal
sulcus whilst the posterior
portion originates from the
middle of the curved lunate
sulcus, or from a curved portion
of the transverse occipital
sulcus if absent.

76. 6. LIMBIC LOBE
• The limbic lobe includes large parts of the
cortex on the medial wall of the
hemisphere, principally the subcallosal,
cingulate and parahippocampal gyri. It
also includes the hippocampal formation
• The hippocampal formation consists of
the hippocampus proper (Ammon’s horn
or ‘cornu ammonis’), the dentate gyrus,
the subicular complex (subiculum,
presubiculum, parasubiculum) and the
entorhinal cortex.
• There is a close relationship between
these phylogenetically old cortical
structures and the termination of the
olfactory tract in the frontal and medial
temporal lobes.

78. Cingulate Gyrus

79. Parahippocampal Gyrus
• The parahippocampal
gyrus includes areas of
entorhinal and medial
temporal cortical fields.
• It has complex
interconnections with the
cingulate cortex and with
the hippocampal
formation.
• It surrounds the
hippocampus

80. Entorhinal Cortex
• The entorhinal cortex (EC) is an
area of the brain located in
the medial temporal lobe.
• located at the caudal end of
the temporal lobe
• Divided into Lateral and Medial
Entorhinal cortices.

81. Hippocampal
Gyrus
• The hippocampus
lies above the
subiculum and
medial
parahippocampal
gyrus, forming a
curved elevation,
approximately 5
cm long, along
the floor of the
inferior horn of
the lateral
ventricle

86. Subcallosal Gyrus
• The subcallosal
gyrus (paraterminal
gyrus, peduncle of the corpus
callosum) is a narrow lamina
on the medial surface of the
hemisphere in front of
the lamina terminalis, behind
the parolfactory area, and
below the rostrum of
the corpus callosum. It is
continuous around the genu of
the corpus callosum with
the indusium griseum.

87. Indusiem Griseum
• The indusium griseum, (supracallosal
gyrus, gyrus epicallosus) consists of a
thin membranous layer of grey
matter in contact with the upper
surface of the corpus callosum and
continuous laterally with the grey
matter of the cingulate cortex.

89. • The amygdala (amygdaloid nuclear complex) consists of lateral, central and basal nuclei that
lie in the dorsomedial temporal pole, anterior to the hippocampus, close to the tail of the caudate
nucleus and partly deep to the gyrus semilunaris, gyrus ambiens and uncinate gyrus.
• Collectively the nuclei form the ventral, superior and medial walls of the tip of the inferior horn of
the lateral ventricle. The amygdala is partly continuous above with the inferomedial margin of the
claustrum.

93. Thank You!
See you soon.