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Today we will continue with the ventricular system and the vasculature of

the brain .. also the cranial nerve ( the material that is required for the

cranial nerve is the table that is in the book ) ..( you must know the Latin

number of each nerve , the name of each nerve , from which foramen does it

pass and the main function )

Today we will move inside the brain .

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

of 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 the

csf (cerebrospinal fluid )

** We have two large champers that are inside the cerebrum at both sides

of the cerebrum in the right and left hemispheres we call them the lateral

ventricles (they are the first and the second ventricles)

** then there is a smaller one in the middle in the level of the diencephalons

between 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 hind

brain between the pons and medulla oblongata anteriorly and cerebellum

posteriorly , we refer to it the fourth ventricle

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

choroid plexus

So what is the coroid plexus ??

- plexus is a capillary network

- Choroid oid means like its a greek word that means like coroin you

remember the coroin from the previous semester coroin means skin so it`s

like a skin because there are cells .

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Contributing to this plexus those are similar to the cells forming the skin

which are the epithelial cells so there is a epithelial coroid cells we call

them epindymal cells

So the choroid plexus is formed by

1- 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 in

the subarachnoid space between the archnoid and the pia matter now when

the cerebral artery send a branch inside the brain the branch will continue

all the way to the champers

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

capillaries

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 of

the champer )

So once the blood capillary there the plasma fluid start to filtrate from the

blood capillary through pia matter then through the epindymal cell to inside

that champer

So the filter are those three layers

1- the wall of the blood capillary

2- pia matter

3- 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 pass

is the clear colourless fluid which is the plasma fluid once the fluid filtrate

through these filters , it will enter into the ventricle , its there the plasma

fluid is called the cerebrospinal fluid

** so what is the coroid plexus ?

its form from there layers

1- the wall of the blood capillary

2- pia matter

3- epindymal cells

** what`s happening there ?? the arteriole gets inside the champer and

take 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 large

cavities that are filled with the CSF and they usually communicate with the

third 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 this

membrane is transparent membrane, so that is why they called it SEPTUM

PELLUCIDUM.

When you look to the brain medially ,you will find that the left &righthemisphere of the cerebrum ,and the longitudinal fissure end in white

matter (that is mean : mylinated axons) ,this is what we call it

CORPUS CALLOSUM : *Corpus: body

*callosum : hard so it is very hard body formed by mylinated axons

that 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 third

ventricle (which is located at the midline below septum pellucidum).

The 2 lateral ventricles have a small opening to drain the CSF into third

ventricle, this opening called: interventricular foramina (2 in number).

So interventricuar foramina communicate the 2 lateral ventricles with the

third ventricle.

NOW WE REACH THE THIRD VENTRICLE

it is locates within diencephalon below the septum pellucidum, in the midline

between 2 masses of thalamus.

When you look to this chamber, you will see that it is penetrated in the

center 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 interthalmic

connection (which passes through the third ventricle).

Border of third ventricle :

**lateral wall

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NOW, THE FORTH VENTRICLE

it is the smallest chamber that is located in the hindbrain between brain

stem

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For the amount and the pressure of CSF within the meninges and the brain

so :

How it return back to the circulation?

By arachnoids granulations ( extension from arachnoid they exit from the

arachnoids to go over the meningeal layer of dura Now Between dura and

bone there is a vein (superior sagittal sinus) arachnoids extend and go to the

sagittal sinus. now when it is there the CSF start to filtrate from inside to

outside (from subarachnoid space back to the veins (sinuses) this is what we

call 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, from

here it will filtrate back into the venous circulation.

so CSF produced here, but the CSF enter the sagittal sinus its reabsorbed

back into the venous circulation again so this is how it going.

They filtrate with in the ventricles to the subarachnoid space >> then they

filtrate 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 the

CSF will lead to increase amount of CSF and increase the intracranial

pressure.)

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 secretion (the arachnoid granulation damaged) there is no filtration

of CSF.

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So there is excess of the CSF in the ventricles, that will lead to enlargement

of the head in small children; because in the children there are no complete

calcification of the bone (soft tissue).

In the adult the skull and the sutures already closed so there is no

enlargement in the head instead there is severe pain and damage of the

tissue of the brain in the adults.

Another case >> small baby that has fall down from her bed to the ground

>> her head is injured and there was an occlusion into inflammation inside

the brain .

The foramina will close in the fourth ventricles so the fluid start to

accumulate and the head start to enlarge.

Artery in the brain:

The blood supply in the brain is very

important:

2 ICA

2 Vertebral a.

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1- ICA:

Continuation of the CCA in the carotid sheath (providing blood supply to all

anterior superior part of the brain).

2- Vertebral A:

A branch from the first part of the subcalvian (providing blood supply to the

inferior 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:

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( it will go to the orbit) through optic canal with optic nerve, then it

enters and it will provide blood supply to the most structure within the

orbit to give supraorbital and supratrocheolar artery, that provide blood

supply 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 )

It usually will go and run inside the longitudinal fissure, then they loop

around the corpus callosum to provide blood supply to the most medial

surface of the frontal and parietal bone.

So they run in the longitudinal fissure: to provide blood supply to the

medial surface of the cerebrum until parieto-occipital sulcus, and at the

level 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 largest

branch of the ICA >> it will run in the lateral sulcus ( they separate the

temporal from the parietal and frontal lobe ); so it will go laterally then

it will go posteriorly with in the lateral sulcus to provide blood supply to

the most of the lateral aspect of the brain.

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There is posteriorly communicated branches they are small one coming

from the ICA to communicate to the posterior cerebral artery .

and there is a coriadel Artery ,, they will penetrate the brain tissue to

the ventircls to form coride pleux .

Vertebral Artery :

arise from the subclavian artery and they enter the skull through what we

call if Foramen Magnum , after that they will be pass over the Medulla

Oblengata lowest part of the brain

at the junction btw the Medulla and the pons at the junction the 2 vertebral

artery 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

artery start from junction btw the medulla oblongata and the poins

terminate to posterior cerebral artery .

Ones it is arise there it will go posteriorly over the middle surface of the

brain provide blood supply it .

the vertebral artery again when they get in the foramen magnum they get to

provide several branches :1. Pos . meningeal artery : dura mater

2. Ant and pos spinal artery : spinal cord

3. Inf.cerebal artery : cerbulum

4. Medullary artery : medulla oblongata

* Basilar artery *

over the bones first of all it will give us a very important branch

ant, inf , cerebral artery and then what we call lapyrinthine artery

go all the way to the inner ear ,, cerebellum artery to the cerebellum

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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 and

vesteblococcya check the spilling nerves to the internal

acoustic meatus supply the inner ear .

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pontine artery : go to the pons

pos cerebral artery : turns back ward of midbrain supply :

1. Occipital lobe

2. Inf. Part of temporal lobe

3. Middle part of the temporal lobe

all of these artery because of the importance of the blood supply

the brain tissue contribute to the 2.5% of the tissue mass in the

body BUT 20% of O2 in the body supply only the brain .

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Circulus Arteriosus

Circle of Willis

Why ?! if one of the arterys that supply the brain is occluded either the basilar or the

ICA 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 2

anterior 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 and

vertebral artery .

regard to the cranial nerves you should just distinguished in the lab

you have to know the origin and the skull foramina of each cranial nerve and the

main 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 , Sondos

Harbieh

forgive us if you find any Mistakes :)

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