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Today we will continue with the ventricular system and the vasculature ofthe brain .. also the cranial nerve ( the material that is required for thecranial nerve is the table that is in the book ) ..( you must know the Latinnumber of each nerve , the name of each nerve , from which foramen does itpass and the main function )

Today we will move inside the brain .

* in the brain we have champers we refer to them as ( ventricular systemof the brain )

* The champers are 4 in number and we call them .>>> ventricles

* they are very important because they form the area of production of thecsf (cerebrospinal fluid )

** We have two large champers that are inside the cerebrum at both sidesof the cerebrum in the right and left hemispheres we call them the lateralventricles (they are the first and the second ventricles)

** then there is a smaller one in the middle in the level of the diencephalonsbetween the two masses of the thalamus we refer to it the third ventricle

** the last one and the smallest that located down of the mid brain( because it`s so small and we can`t put a champer there ) , in the hindbrain between the pons and medulla oblongata anteriorly and cerebellumposteriorly , we refer to it the fourth ventricle

* Within these champers the csf is produced from what we call it thechoroid plexus

So what is the coroid plexus ??

- plexus is a capillary network

- Choroid oid means like its a greek word that means like coroin youremember the coroin from the previous semester coroin means skin so it`slike a skin because there are cells .

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Contributing to this plexus those are similar to the cells forming the skinwhich are the epithelial cells so there is a epithelial coroid cells we callthem epindymal cells

So the choroid plexus is formed by1- the capillary network

2- pia matter

3- last layer is the epithelial cells ( epindemal cells )

**So what is happening there that we have a cerebrul artery that is found inthe subarachnoid space between the archnoid and the pia matter now whenthe cerebral artery send a branch inside the brain the branch will continueall the way to the champers

( to one of the champers ) there the artery will start providing bloodcapillaries

So the blood capillary from the inside layer

** from out side there is the pia matter ( it pull it with it when it enters )

** and the last layer is the epindymal layer ( covering the inner surface ofthe champer )

So once the blood capillary there the plasma fluid start to filtrate from theblood capillary through pia matter then through the epindymal cell to insidethat champer

So the filter are those three layers1- the wall of the blood capillary2- pia matter3- epindymal cells

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so these layers will prevent any blood to pass through them ( no platlets ,red blood cell or whithe blood cell can pass ) so the only thing that can passis the clear colourless fluid which is the plasma fluid once the fluid filtratethrough these filters , it will enter into the ventricle , its there the plasmafluid is called the cerebrospinal fluid

** so what is the coroid plexus ?

its form from there layers

1- the wall of the blood capillary2- pia matter3- epindymal cells

** what`s happening there ?? the arteriole gets inside the champer andtake with it the pia matter to inside the champer

** what is the function of the coroid plexus ?

- production of the csf

The lateral ventricles locate within the cerebrum, and they are 2 largecavities that are filled with the CSF and they usually communicate with thethird ventricle.

There is membrane separates these 2 lateral ventricles from each other,and if you look to this membrane (from above), you will find that thismembrane is transparent membrane, so that is why they called it SEPTUMPELLUCIDUM.

When you look to the brain medially ,you will find that the left &righthemisphere of the cerebrum ,and the longitudinal fissure end in whitematter (that is mean : mylinated axons) ,this is what we call itCORPUS CALLOSUM : *Corpus: body*callosum : hard so it is very hard body formed by mylinated axonsthat make interconnection between the right and left cerebrum together

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below it immediately we have what it is called septum pellucidum.(Septum: means wall , pellucidum: means transparent ).

Inferiorly, the 2 lateral ventricles will drain their CSF throughsmall formin to the thirdventricle (which is located at the midline below septum pellucidum).The 2 lateral ventricles have a small opening to drain the CSF into thirdventricle, this opening called : interventricular foramina (2 in number).So interventricuar foramina communicate the 2 lateral ventricles with thethird ventricle.

NOW WE REACH THETHIRD VENTRICLEit is locates within diencephalon below the septum pellucidum, in the midlinebetween 2 masses of thalamus.When you look to this chamber, you will see that it is penetrated in thecenter by brain tissue which is connect 2 masses of thalamus (right &left),this is what we call it INTERTHALAMIC CONNECTION.The thalamus consider one unit of brain tissue, but it has to halves(right&left), in 70%, both halves connect with each other by interthalmicconnection (which passes through the third ventricle).

Border of third ventricle :**lateral wall

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NOW, THE FORTH VENTRICLEit is the smallest chamber that is located in the hindbrain between brainstem

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For the amount and the pressure of CSF within the meninges and the brainso :

How it return back to the circulation?

By arachnoids granulations ( extension from arachnoid they exit from thearachnoids to go over the meningeal layer of dura Now Between dura andbone there is a vein (superior sagittal sinus) arachnoids extend and go to thesagittal sinus. now when it is there the CSF start to filtrate from inside tooutside (from subarachnoid space back to the veins (sinuses) this is what wecall it:

(arachnoids granulations): villi; which is an extension of arachnoid matter all

the way towards the sagittal sinuses then they extend to go to the veins andthen the CSF pass through these spaces within into go to the vein, fromhere it will filtrate back into the venous circulation.

so CSF produced here, but the CSF enter the sagittal sinus its reabsorbedback into the venous circulation again so this is how it going.

They filtrate with in the ventricles to the subarachnoid space >> then theyfiltrate back to the sagittal sinuses >> to the Internal jugular vein to the

venous circulation ( CSF circulation or arachnoid circulation).

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Avery important condition ( hydrocephalus)

(Hydro: water, Cephalus: head )

Excess CSF in the ventricles leading enlargement of the head

Causes:

1. overproduction

2. obstruction of CSF flow

3. interference with CSF absorption

Results in infants:

the head in size

If the circulation of the CSF has some problems (e.g.: over production of theCSF will lead to increase amount of CSF and increase the intracranialpressure.)

The foramen in the fourth ventricle that connect the CSF within the Brain

into the subarachnoid space (foramen of luschka , magendie ) >> they may beblock so the CSF will accumulate inside the brain.

Or the excretion (the arachnoid granulation damaged) there is no filtrationfrom subarchnoid space into the vinous sinuses

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So there is excess of the CSF in the ventricles, that will lead to enlargementof the head in small children; because in the children there are no completecalcification of the bone (soft tissue).

In the adult the skull and the sutures already closed so there is noenlargement in the head instead there is severe pain and damage of thetissue of the brain in the adults. "which may lead to death if not treated "

Another case >> small baby that has fall down from her bed to the ground>> her head is injured and there was an occlusion due to inflammation insidethe brain, The foramina will close in the fourth ventricles so the fluid startto accumulate and the head start to enlarge.

Artery in the brain:

The blood supply in the brain is veryimportant:

[A] 2 ICA

[B] 2 Vertebral a .

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1- ICA:

Continuation of the CCA in the carotid sheath (providing blood supply to allanterior superior part of the brain).

2- Vertebral A:

A branch from the first part of the subcalvian (providing blood supply to theinferior posterior part of the brain).

*The ICA when it enters by the Carotid canal to inside the skull and theyusually will provide 5 arteries:

1- ophthalmic artery:

( it will go to the orbit) through optic canal with optic nerve, then itenters and it will provide blood supply to the most structure within theorbit to give supraorbital and supratrocheolar artery, that provide bloodsupply to the forehead .

(This artery not much related to the brain)

But the remaining ones related to the brain:

2- anterior cerebral artery : (the most anterior one )

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It usually will go and run inside the longitudinal fissure, then they looparound the corpus callosum to provide blood supply to the most medialsurface of the frontal and parietal bone.

So they run in the longitudinal fissure: to provide blood supply to themedial surface of the cerebrum until parieto-occipital sulcus, and at thelevel of this sulcus they will terminate .

3- the other one is the middle cerebral artery :

because it is situated in the middle part of the brain and it is the largestbranch of the ICA >> it will run in the lateral sulcus ( they separate thetemporal from the parietal and frontal lobe ); so it will go laterally thenit will go posteriorly with in the lateral sulcus to provide blood supply tothe most of the lateral aspect of the brain.

There is posteriorly communicated branches they are small one comingfrom the ICA to communicate to the posterior cerebral artery .and there is a coriadel Artery ,, they will penetrate the brain tissue tothe ventircls to form coride pleux .

Vertebral Artery :

arise from the subclavian artery and they enter the skull through what wecall if Foramen Magnum , after that they will be pass over the MedullaOblengata lowest part of the brainat the junction btw the Medulla and the pons at the junction the 2 vertebralartery from both side will join together form a larger artery what we call it basilar artery so this artery is a large branch by the union of vertebral

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artery start from junction btw the medulla oblongata and the poinsterminate to posterior cerebral artery .Ones it is arise there it will go posteriorly over the middle surface of thebrain provide blood supply to the mideal surface of the temporal andoccipital lope .

the vertebral artery again when they get in the foramen magnum they get toprovide several branches :1. Pos . meningeal artery : dura mater2. Ant and pos spinal artery : spinal cord3. Inf.cerebal artery : cerbulum4. Medullary artery : medulla oblongata

* Basilar artery *over the bones first of all it will give us a very important branchant, inf , cerebral artery and then what we call lapyrinthine artery go all the way to the inner ear ,, cerebellum artery to the cerebellum

pontine artery : go to the pons

pos cerebral artery : turns back ward of midbrain supply :1. Occipital lobe2. Inf. Part of temporal lobe3. Middle part of the temporal lobeall of these artery because of the importance of the blood supplythe brain tissue contribute to the 2.5% of the tissue mass in thebody BUT 20% of O 2 in the body supply only the brain .

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Lapyrinthine Artery :15% of it from basilar artery and 85% from anterior inferiorcerebellar artery .Importance : go to the lapyrinth all the with the facial andvesteblococcya check the spilling nerves to the internalacoustic meatus supply the inner ear .

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Circulus ArteriosusCircle of WillisWhy ?! if one of the arterys that supply the brain is occluded either the basilar or theICA with the prncess of this circle the blood supply to the brain continue .

Anastomosis between branches of 2 ICA & 2 vertebral artery

Within the brain , consist anteriorly with anterior communicating artery which the 2anterior cerebral artery .

ant. Cerebral a.

ICA

Post. Communicating a

post. Cerebral a.

basilar a.

the only artery that dont contribute to the circle is middle cerebral artery andvertebral artery .

regard to the cranial nerves you should just distinguished in the labyou have to know the origin and the skull foramina of each cranial nerve and themain function the are 12 pairs not all of them arise from the brain accessory nerve

arise from the spinal cord go all the way to the foramen magnum and the jugularforamina , they are part of the PNS

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Done by : Heba saleh Radiadeh , Haya Momani , Weam Rahamneh , SondosHarbieh

forgive us if you find any Mistakes :)

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