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Internal structures of
hemispheres
‫ أيمن أبوطبنجة‬.‫د‬
‫سـاجدة فردوس‬
Anatomy
3+4 1
Greetings awn…
Lecture objects : slides (24-53)
Internal structures of hemispheres
Ventricles
CSF
Functional localization of cerebral
cortex
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Internal structures of cerebral hemispheres
Today we’ll continue our talk about projection fibers .
*Definition : fibers that connect the brain stem to cerebral hemisphere (cortex to
be specific ) , and these fibers are going to either directions ( from cortex to brain
stem and vise versa ) .
*They have different name due to different location :
❶Corona radiata :
-Location: above ( superior / dorsal ) basal nuclei .
(radiations) .
- divided into segments
-Eg. optic radiation is going to optic cortex , auditory radiation …etc
❷Internal capsule(white matter ) : has 2 limbs»» posterior limb between
lentiform nucleus and thalamus , anterior limb between lentiform and
caudatenucleus . Between 2 limbs there is a structure like a knee»» the genu of
internal capsule .
❸External capsule : between lentiform and claustrum .
❹ Extreme capsule : between claustrum and insula .
At
level
of
basal
nuclei
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Basal nuclei : masses of grey matter embedded in white matter .
Note that the cortex isn't considered as a basal nuclei because it
isn't embedded in white matter.
Lentiform nucleus composed of putamen (laterally) +
globuspallidus(medially) .
Thalamus:sensory station of the body /not a part of basal nuclei /
used as alandmark to define different projection fibers .
Claustrum : thin line of grey matter / its function isn't well known
Insula : parts of cortex folded inside lateral sulcus .
*Other internal structures of cerebral hemisphere :
❶septum pellucidum(double membrane) : delicate membrane(you can tear it
and find a space “part of anterior horn of lateral ventricle” ) that bounded by
corpus callosum superiorly and fornix (bundles of fibers that originate from
hippocampus ) inferiorly .
Remember we can’t see hippocampus because it is
Hidden inside the temporal lobe .
*Inner surface of septum pellucidum composed of ependymal cell, because this
surface considered as part of the wall of the lateral ventricle.
*we have 2 septum pellucidum (cavumpellucidum separate between them).
*it’s the medial wall of anterior horn of lateral ventricle .
*composed of both gray and white matter . (although it appears white in fresh
specimen of brain ) .
❷corpus callosum : the largest bundle of commissural fibers .
*composed of : 1.rostrum (the smallest) 2.genu(most anterior)
3.body( the largest) 4.splenium(most posterior) .
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Ventricles
❶Four CSF-filled cavities located within the brain .
❷Lined by ependymal cells .
❸Contain specialized vascular structures called :choroid plexuses »» synthesis of
CSF .
*We have 2 lateral ventricles ; one in each hemisphere , 3rd ventricle in
diencephalon , 4th in hindbrain and cerebral aqueduct in midbrain .
*C-shaped of lateral ventricle to allow it to extend to all lobes of brain .
* Each lateral ventricle is connected to 3rd ventricle by foramen of monro (or
interventicular / 2 in number )
*3rd ventricle connected to 4th by cerebral aqueduct then continue as central
canal of spinal cord .
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❶Lateral ventricles : Parts :
Body » in parietal lobe .
Ant.horn » in frontal lobe .
Post. Horn » in occipital lobe .
Inf. Horn » in temporal lobe .
Note: horns also can be named according to the part they are located in… for
example the posterior horn can be called " occipital horn" and so on 
❷3rdventricle : narrow cavity between 2 thalami or inside diencephalon .
*If we fix both halves of the brain the 2 thalami will not occlude ‫ ال تنطبق‬, there
will be a space »» 3rdventricle, and it is also located medially to the "C" shaped
lateral ventricle.
*Interthalamic connection : Bridge of tissue running through the 3rd ventricle
connecting the 2 thalami .
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❶First picture : anterior coronal section ; why ?
Notice the temporal lobe,thalamus and optic nerve . If we were in the middle we will see optic chiasma .
Notice the spaces which resemble anterior horn of lateral ventricles and they seperated by corpus
callosum (genu) .
❷Second picture: ( fyrther medial section ; why ?
Notice thalamus , 3rd ventricle (the body) .. and the searation between the two lateral ventricles is done
by septum pellicidum.
Third picture:
Here we cant see any part of the temporal lobe so it's the occipital, the postrior horn of the 3rd ventricle
is visible here, also the splenuim of corpus callosum is seen in this section.
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❸Cerebral aqueduct :
¾ inch long , Connects third ventricle to
fourth ventricle, Does not contain choroid
plexus .
❹4th ventricle :
Tent shaped cavity , Anterior to cerebellum.
Posterior to pons and medulla oblongata which Communicates with central canal
of medulla and spinal cord .
Communicates with subarachnoid spacethrough:
-foramen of magendie(1 in number) » central .
-foramen of luschka (2 in number ) » lateral .
T1 weighted MRI (used more)
T2 weighted MRI:
to visualize grey and while matter:
CSF appears white .
CSF appears dark .
Fluid is translucent .
fluid is radiopaque
used if we are looking for bleeding or edema
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Choroid plexuses :
Invagination of pia matter with blood
caplliries inside it, found through
ventricles .
*Components :
-Endothelial layer(fenestrated)
-Pial membrane.
-Choroidal epithelial cells (at the top ) :
form the blood -CSF barrier and
responsible of active transport of the
substances in and out of CSF .
This is an electron micrograph of
choroidal cells , notice the dark points(
tight junction ).
*the luminal aspect of cells are tightly
adherent to Each other to prevent any
passive movement of Materiales .
CSF
❶Made by choroid plexus : 500 ml/day(rate of production) .
❷Active process because of the tight junctions between the choroidal epithelial
cells.
❸Distributed in ventricles and SAS(subarcnoid space)
❹Clear and colorless .
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*We have 150 ml of CSF in our body due to high turnover.
*Only 20 ml of CSF in ventricles (less than 50%).
*We need to keep brain in soft , fresh CSF which full of nutreints and electrolytes
*The production of CSF is an active process because choroidal epithelial cells are
connected by TJ .
*The vast majority of CSF exists in SAS .
*CSF share many components with
serum , with some execptions :
❶CSF protiens is very low compared
to serum .
❷CSF glucose is half of plasma .
❸Minor differences in electrolytes .
*Functions of csf :
❶Provide neural tissue with nutrients
and aqueous solution .
❷Necessary for generation of action potential .
CSF circulation :
❶The CSF formed in the coroid plexuses of each lateral ventricle flows into the
3rd ventricle through Interventicular foramina .
❷Then flows from 3rd to cerebral aqueduct to 4th ventricle .
❸From 4th ventricle a small amount of CSF passes downward into the central
canal of the spinal cord
While the majority enters the SAS through 3 openings (as mention earlier )
*All SAS is continous with each other , with some exeptions(larger than other) :
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❶Cisterna magna:receive CSF by
foramen magendi ,just below the
cerebellum.
❷Pontine cistern :which located
around pons .
❸Interpeduncular cistern:
anterior aspect of midbrain.
❹Superior cistern (Quadrigeminal
cistern): posterior aspect of
midbrain.
*Cistern: Any opening in the subarachnoid space of the brain created by a
separation of the arachnoid and pia mater. These spaces are filled with CSF
*wiki*, and was defined by the doctor as a part of the SAS larger than its
surroundings… (both are correct )
*Some CSF will go up by the pulsations of arteries of SAS by the movement of the
vertebral column.*The same pulsations will move CSF slowly around the lateral &
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medial surface of the brain, until ultimately CSF is secreted into Dural sinuses by
Arachnoid villi , most of the CSF will end up
In the superior sagittal sinus.
note: there is no choroid plexus in the SAS
Aracnoid villi : are projections of the arachnoid matter into the Dural venous
sinuses .
*Valve-like function mean: one way circulation ; because we don’t want blood to
mix with CSF .
*Through hydrostatic pressure csf will flow from SAS into superior sagittal sinus .
♪If hydrostatic pressue decreases in SAS or increased in venous sinus , what will
happen ? aracnoid villi will collapse(to prevent any mixing) .
Hydrocephalus : ( incomplete CSF circulation)
*Accumlation of CSF / internal or external(depending on location) .Eg.if there is a
tumor in cerebral aqueduct and it gets Block » there will be an accumlation of CSF
in 3rd and 4th Ventricles .»internal .(as pictures)… this pushes the brain preventing
its growth resulting in neurological deformities  . . see the MRI image
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*If it’s external the accumlation will be between skull and brain tissue ( in the
SAS) .
Functional localization of cerebral cortex
*These numbers resembled brodmann areas .
*Many scientists studied the cellular morphology of the cortex ,and based on the
types they found they divided the cortex intoregions , ( some studies divided the
cortex into 20 regions , otherstudies reached as far as 200 regions ) .
* The most famous of these studies is the one which was done by Brodmann (
divided the cortex into 52 regions ) .
*Brodmann studied the morophology and the cellular aggregation in the cortex
*Later on when they studied the function they found for example that some
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Brodmann regions are related to a function , in other situations we have multiple
Brodmann regions related to the same function .
in the past they used to lesion the cortex to know the function of a certain area in the it, later
they measure the electrical activity in the brain when stimuilating the sight for exmple.
*ps:you must memorize brodmann areas *
❶General Somatic Sensations ( tempreture, pain …) :
Primary somesthetic area:this area allows u to feel the particular sensation ,
whether it is touch , pain … etc.
*Location:
-Postcentral gyrus in the lateral surface.
-Posterior part of paracentral lobule in the medial one.
(Brodmann areas 1,2,3).
Somesthetic association cortex:this area allows you to integrate your past
experience with sensation .
* for example:if I'm holding something in my
hand , the touch feeling is done by the primary
area , now if I'm not looking at that subject ,
and just by touching the object I'm realizing
what is it , this integration of the sensation is
done by the secondary area .
*Location:
-Superior parietal lobule.
(brodmann areas 5, 7).
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❷Vision :
Primary visual cortex:this area allows me to detect that there is an object in the
class room /allow me to see in gray and white color.
-Surrounds calcarine sulcus(located in the medial aspect of the brain , ( in the
occipital lobe )) .
(Brodmann area 17)
Secondary visual cortex: know the identity of an object / color processing .
-Surrounds primary visual area
(Brodmann areas 18, 19).
❸Hearing :
Primary auditory cortex:in order to see the Primary auditory cortex you need to
open the lateral sulcus, then look at the inferior limb of the lateral sulcus , u will
see2 gyri , most of the time they look like they are going inside thebrain.
-Inferior wall of lateral sulcus(Transverse Gyri of heschl’s)
(Brodmann areas 41, 42)
•Secondary auditory cortex : when we talk about the association auditory cortex
we are talking only about the posterior part of superior temporal gyrus(
Brodmann area 22 ),which is called Wernicke's area , or it is called sensory speech
area .it allows you to comprehend what people are saying to you ,if this area is
injured it is look like that all people are speaking a foreign language you never
heard about …. in fact we have one Wernick's area
*wernick’s area exists in dominant hemisphere .
*wernick’s homologue exists in non-dominant hemisphere .
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Allow you to understand the unusual use of the words (eg.if I say bank you
can understand it by wernick’s area , while if I say river bank _side of river _ it’s
unusal term processed by wernick’s homologue ).
❹Taste and olfaction:
Primary gustatory cortex:you trace the post central gyrus until you reach the
lateral sulcus , u open the lateral sulcus and continue in the superior fold , at that
location is the gustatory cortex .
-lower end of postcentral gyrus in the superior wall of lateral sulcus
(Brodmann areas 43).
•Primary olfactory cortex
-Insula and uncus:®part of the cortex is folded inside the lateral sulcus , this
convolution of the cortex inside the lateral sulcus is called the insula® , ®at tip of
para hippocampal gyrus we have a structure , this structure is called the uncus® .
Notice that both th insula and uncus have the same Brodmann's number
indicating that they have the same cellular morphology.
(Brodmann area 34).
❺Motor cortex : in frontal lobe .
Primary motor cortex:responsible for executing the movement in the contalateral
part of the body .
-Precentral gyrus (lateral)
-Anterior part of paracentral lobule (medial)
(Brodmann’ s area 4)
•Secondary motor cortex:responsible for coordinating (integrating ) sensory input
,to allow the sensory input to influence the movement /also responsible for
programming skilled movement .
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*We have :
- One in the lateral surface called " premotor area " .
- One in the medial surface called " supplementary motor area " .
-Lateral aspect of frontal lobe
(Brodmann’ s area 6)
*If a part of secondary motor cortex destroy , doesparalysis happen ? NO
*secondary motor cortex need much stronger electrical signals compared to
primary, but if we destroyed any part of the primary motor cortex definetely we
wil have paralysis in a certain part of the body.
❻ Expressive speech area : allow me to formulate words , so the primary motor
area allows me to move my tongue while the secondary ones makes those
movements coordinated.
-Broca’s area in dominant hemisphere , while broca’s homologue in nondominant hemisphere (add emotions to our words) .
-Consist of Opercular & triangular gyri, in the lateral surface in which this specific
area is divided by rami into those two gyri
(Brodmann’s areas 44, 45)
❼Frontal eye field :responsible for the saccadic eye movement ; the tracking
movement of the eye , if some object is moving and I'm tracing it with my eyes
the movement has certain pattern ,we call it saccadic eye movement (motor
supply of ur occular muscles)
-Lateral aspect of frontal lobe
-Brodmann’ s area 8
*Supplementary motor area
-Medial surface of frontal lobe
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-Brodmann’ s area 6 .
*What about the rest of the frontal lobe ? We call it prefrontal cortex , this is the
part of the cortex that determines your identity ;your behaviors and your attitude
, are all mediated by your prefrontal cortex .
…………………………………………………………………………..
Done by : sajeda akram ferdous .
Special thanks to : Batool and Raghad
I dedicate this sheet to all of you AWN .
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