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CEREBRUM CEREBRUM ANDAND
BASE OF THE SKULLBASE OF THE SKULL
BYDR MANAH CHANDRA CHANGMAI
IMS
Able to describe the general structure of the Cerebrum and Cerebral Cortex.
Able to identify the Cerebrum, the Lobes of the Brain, the Cerebral Cortex, and its major regions/divisions.
Able to describe the primary functions of the Lobes and the Cortical Regions of the Brain.
Objectives
INTRODUCTIONINTRODUCTION
The cerebrum is the largest part of the brain with two hemisphere.The two cerebral hemisphere are linked by commisural fibres of corpus callosum.
Each cerebral hemisphere contains externally highly convulated cortex of grey matter and internal mass of white matter or medulla.
Each cerebral hemisphere contains lateral venticle continous with the third ventricle through interventricular foramen.
The cerebral hemispheres contains motor and sensory areas and the limbic system.
Each cerebral cortex is often divided phylogenetically into old allocortex,consisting of archicortex and paleocortex and a newer neocortex.
Longitudinal Fissure
Cerebral hemisphere
Cortex and medullaCortex and medulla
Surfaces of cerebral hemisphereSurfaces of cerebral hemisphere
Each cerebral hemisphere has three surfaces
I. Superolateral surfaceII. Medial surfaceIII. Inferior surface. Inferior surface further
divided into twoi. Orbital surfaceii. Tentorial surface
Surfaces of cerebral hemisphere………contd.
Superolateral surface It follows the concavity of the cranial vault Medial surface It is flat and vertical and seperated from its fellow by the great
longitudinal fissure and falx cerebri. Inferior surface Inferior surface or the basal surface is irregular and divided
into orbital and tentorial surface.
SuperolateralMedial surface
Surfaces of the brain
Inferior surface
Orbital surface
Tentorial surface
Borders of cerebral hemisphereBorders of cerebral hemisphere
Superomedial border
Inferior border
Occipital pole
Frontal pole Temporal
pole
Poles of the brainPoles of the brain
Lobes of the brainLobes of the brainFour lobes
are present• Frontal• Parietal• Occipital• Temporal Occasionally
insula is considered as the fifth lobe
Gyrus and sulcusesGyrus and sulcuses
Each cerebral hemisphere shows a complex pattern of convulation called Gyrus
The gyruses are separated by furrows of varying length called Sulci.
The convulated structure increases the cortical volume to three times what it would be if the surface is smooth.
The area of the cerebral cortex is 2200cm²
Sulci(Groove)
Fissure(Deep groove)
Gyri(Elevation)
Important sulci and gyriImportant sulci and gyri
In the suprolateral surface:i. Lateral sulcuso Deep cleft on the lateral
and inferior surfaceo It has a stem which divides
into three rami:anterior,ascending,p-osterior.
o The floor of the posterior ramus is the insula which is hidden cortex.
Lateral sulcus
Central sulcus
Important sulcus and gyrus…….contd.
ii. The central sulcuso It is the boundary between frontal and parietal lobeso It starts at the superomedial border, a little behind the
midpoint between frontal and occipital poles.It runs downards and forwards for about 8-10cm to end little above the posterior ramus of lateral sulcus.
o It demarcates the motor and sensory area of the cerebral cortex.
iii. The other known sulcuses are superior frontal sulcus Inferior frontal sulcus Precentral sulcus Postcentral sulcus
Medial surfaceMedial surface
In the medial surface The commisural fibres of
the corpus callosum lies in the depth of longitudinal fissure
Parts of corpus callosuma. Rostrumb. Genuc. Trunk or bodyd. Splenium The anterior part divided
into outer and inner zone by cingulate sulcus
splenium
Body or trunk
GenuRostrum
Medial surface with corpus callosum
Cingulate sulcus
Parieto-occipital sulcus
Calcarine sulcus Collateral sulcus
Sulcus in the medial surface
Sulcus and gyrus………contd.
The posterior region of the medial surface is traversed by parieto-occipital and calcarine sulcus.The parieto-occipital sulcus marks the boundary between parietal and occipital lobes.
The visual cortex lies above and below the calcarine sulcus.
In the inferior cerebral surface Olfactory sulcus Rhinal sulcus Occipitotemporal sulcus Collateral sulcus
Orbital sulcus
Occipitotemporal sulcus
Collateral sulcus
Rhinal sulcus
Sulcus and important structures on inferior surface of cerebral hemisphere
Olfactory sulcus
Insula
-Present within the lateral sulcusBetween temporal and frontalLobe.
-The overlying cortical areas are called opercula formed from the parts of frontal,temporal and parietal lobe
-Functions linked to emotion and body’s homeostasis
-i.e perception,motor control,self awarness,congnitive functioning interpersonal experience
Insula
Cerebral cortexCerebral cortex
Cerebral cortex is an intricate blend of nerve cells and fibres,neuroglia and blood vessels.
Microscopically the cortex consists of six layers or laminae lying parallel to the surface.
From outside to insideI. Molecular or plexiform layerII. The external granular layerIII. External pyramidal laminaIV.Internal granular layerV. Internal pyramidal cell layerVI.Multiform or pleiomorphic layer
Pyramidal cells
Neocortex has 6 layers designated I, II, III, IV, V, VIPyramidal cells predominate in layers III and VGranule cells in layers II and IV
Pyramidal cells
Granule cells
Cerebral cortex
Pyramidal cells have large apical dendrite and basal dendritesAxon projects downward into subcortical white matter; may have collateralsPyramidal cell is the primary output neuron
Pyramidal cell
Pyramidal cell
Pyramidal cell
Broadmann’s areasBroadmann’s areas These areas were defined and
numbered by korbinian broadmann
The areas are based on the cortical cytoarchitectonic organisation of neurons
Many of the broadmann’s areas are defined on neurological function coorelated closely to diverse cortical functions.
For example Area 1,2,3 – primary
somatosensory area Area 4 – Motor area Area 41,42 – Auditory area Area 44,45 – Broca’s area,etc
shou
lde
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legs
toes
ankle
MotorCortex
shou
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toes
genita lia
foot
SensoryCortex
Mapping of sensory and motor areas to the body
•Primary Motor Cortex (Precentral Gyrus) – Cortical site involved with controlling movements of the body.•Broca’s Area – Controls facial neurons, speech, and language comprehension. Located on Left Frontal Lobe.
Broca’s Aphasia – Results in the ability to comprehend speech, but the decreased motor ability (or inability) to speak and form words.
Orbitofrontal Cortex – Site of Frontal Lobotomies
* Desired Effects:- Diminished Rage- Decreased Aggression- Poor Emotional Responses
* Possible Side Effects:- Epilepsy- Poor Emotional Responses- Perseveration (Uncontrolled, repetitive actions, gestures, or words)
Frontal lobes cortical regions
Primary motor cortex
Broca’s area
Orbitofrontal cortex
Primary Somatosensory Cortex (Postcentral Gyrus) – Site involved with processing of tactile and proprioceptive information.
Somatosensory Association Cortex - Assists with the integration and interpretation of sensations relative to body position and orientation in space. May assist with visuo-motor coordination
Primary Gustatory Cortex – Primary site involved with the interpretation of the sensation of Taste.
Parietal lobe cortical areas
Associated somatosensory area(7)
Primary gustatory area (40)
Primary somatosensory area(3, 1, 2)
Primary Visual Cortex – This is the primary area of the brain responsible for sight -recognition of size, color, light, motion, dimensions, etc.
Visual Association Area – Interprets information acquired through the primary visual cortex.
Occipital lobe and cortical regions
White matter of cerebrumWhite matter of cerebrum Consists of myelinated nerve
fibres which are categorized on the basis of their course and connections
A. Association fibres• It links different cortical areas
of the same hemisphere• Two typesi. Short association fibres They are entirely intracotical Some merely pass from one
wall of the sulcus to other.ii. Long association fibres They are present in bundles Example: uncinate
fasciculus,cingulum,superior longitudinal fasciculus,etc
White matter of cerebrum………contd.White matter of cerebrum………contd.
B. Commissural(transverse) fibres
• Commisural fibres cross the midline,linking corresponding areas in the two cerebral hemisphere.
• The largest commissure is the corpus callosum.Other commisures are
a. Anterior b. Posteriorc. Habenulard. Commissure of the fornix.
White matter of cerebrum……..contd.
C. Projection fibres• Projection fibres
connect cerebral cortex with lower levels in the brain and spinal cord.
• Consists of both coticofugal and corticopetal fibres
• Corticofugal fibres converge from all directions to form corona radiata.Corona radiata continous with the internal capsule.
Corpus callosum
Anterior commissure
Habenular commissure
Posteriorcommissure
Commissures of brain
Commissure of fornix
CT SCAN OF THE BRAIN
CT scan of the brain showinga tumour in the right cerebral hemisphere
CT scan of brain…….contd
MRI OF BRAIN
.A non-progressivedisorder• Caused by brain injurypre (70-80%), peri, orpost natally• Injure occurs beforeCNS reaches maturity• Patients often have greatpotential masked by their connections
Cerebral palsy
• Malfunction of motor centers• Postural and balancedifficulties• Normal life expectancypossible• Early death respiratory
Manifestation
Spastic • 52-70% of all CPs• Hyperirritability of muscles• Arms flexed, legs internally rotated• Difficulty bending into a sitting position• Difficulty with head control• Postural difficulty• May not have protective extension
Athetoid or Dyskinetic Type• 25- 30% of CPs• Uncontrollable writhing movements ofopposing muscle groups• All four extremities involved• Neck and face involved• Voluntary movements are flailing• Difficulty uprighting and balancing•Grimacing
• Tremors (rare form) of CP• Rigid 5 -10% of CPs• Flaccid (Hypotonicity)• Mixed 15 - 40% of CPs
• 5 to 10 %• Affects balance and coordination.• They may walk with an unsteady gait with feetfar apart, and they have difficulty withmotions that require precise coordination,such as writing.
Ataxic cerebral palsy
Other types
BASE OF THE SKULLBASE OF THE SKULL
SKULL BASESKULL BASE
Skull base boundaries: Upper surface of the ethmoid bone,orbital plate of the frontal
bone upto the ethmoid bone
Key bones: Orbital Plate of frontal bone Ethmoid bone Sphenoid bone Occipital bone
Skull base……contd.
Divided into three cranial fossa: a. Anterior cranial fossab. Middle cranial fossac. Posterior cranial fossa
Key openings in base of the skull
Foramen spinosumForamen ovaleForamen lacerumForamen rotundumForamen magnumJugular foramenSuperior orbital fissureInferior orbital fissure
Optic canalHypoglossal canalPterygopalatine fossa
Skull base……contd.
Foramen rotundumPresent at the anterior and medial part of sphenoid bone.Structures passinga.Maxillary nerveb.Emissary veins
Foramen ovaleLocated in the anterior part of sphenoid bone,posterolateral to foramen rotundumStructures passing• Mandibular nerve• Accessory meningeal artey• Lesser petrosal nerve• Emissary veins
Foramen spinosumForamen spinosum may be absent in 2% of the cases.Situated posterolateral to foramen ovaleTransmits following structures• Middle meningeal artery•Nervous spinosus from mandibular nerve• Middle meninigeal vein
Foramen magnum Latin”great hole” is present in the occipital boneIt transmits• Medulla oblongata,vertebral arteries• Anterior and Posterior spinal arteries• Spinal accessory nerve•Membrana tectoria,Alar ligaments.
Superior Orbital Fissure
• CN III, IV, V1, VI
• Middle meningeal artery- orbital branch
• Recurrent meningeal artery
• Superior opthalmic vein
Jugular foramen Anterior compartment• Inferior petrosal sinus intermediate compartment• Cranial nerve IX,X,XI Posterior compartment• Internal jogular vein• Meningeal branches of occipital and ascending pharyngeal artery
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