Anatomy of meninges, ventricles, cerebrospinal fluid

MENINGES, VENTRICLES, CEREBROSPINAL FLUID AND BOOLD SUPPLY OF THE BRAIN

Dr. Israa M. SulaimanDr. Mohammed Faez

Department of AnatomyIMS/MSU

OBJECTIVES

• Illustrate and describe the Meninges’s three membranes.

• Describe the structure of the meninges, its blood supply and nerve supply.

• Illustrate and describe the venous blood sinuses

The Meninges

• The Meninges are the membrane covering the brain and spinal cord.

• The Meninges consist of three membranes:

1. The dura mater, 2. The arachnoid mater,3. The pia mater.

The Meninges

The Meninges

1. Dura mater - strong, "Tough mother"a. Falx cerebri b. Falx cerebelli c. Tentorium cerebelli d. Diaphragma sella

• 2. Arachnoid - spidery, holds blood vessels

• 3. Pia mater - "delicate mother"

The Meninges

Sagittal section showing the duramater

1) Falx cerebri

2) Tentorium cerebelli

3) Falx cerebelli

4) Diaphragma sellae

Superior view showing the duramater

1) Falx cerebri


http://yahooligans.yahoo.com/reference/gray/illustrations/figure?id=569

DURA MATER Thick dense inelastic membrane

and the outermost layer of the meninges

Bilaminar:

Endosteal layer (outer)

Meningeal layer (inner)

These are closely united except along certain lines, where they separate to form venous sinuses.

DURA MATER Endosteal layer ;

o Periosteum - inner surface of the skull bones

o Not continuous with dura mater of spinal cord

Meningeal layer ;

o Dura mater proper

o Covering the brain

o Continuous with dura mater of spinal cord

o Folded inwards as 4 septa between part of the brain

o The function of these septa is to restrict the rotatory displacement of the brain.

duramater

Superior cerebral veins beneath arachnoid

Coronal section of the upper part of the head

Endosteal layer

Meningeal layer

They are closely united except along certain lines; they are separated to form venous sinuses

Superior sagittal sinus

(Dural venous sinus)Dura mater

Subdural space

DURA MATER

Dura mater septa:1. Falx cerebri 2. Falx cerebelli3. Tentorium cerebelli 4. Diaphragma sella

Sagittal section showing the duramater

1) Falx cerebri


3) Falx cerebelli

4) Diaphragma sellae

The Falx Cerebri• It is a sickle-shaped fold of dura

mater that lies in the midline between the two cerebral hemispheres.

• Its narrow end in front is attached to the internal frontal crest and the crista galli.

• Its broad posterior part blends in the midline with the upper surface of the tentorium cerebelli.

• The superior sagittal sinus runs in its upper fixed margin, the inferior sagittal sinus runs in its lower concave free margin, and the straight sinus runs along its attachment to the tentorium cerebelli.

Falx cerebriSuperior sagittal sinus

Inferior sagittal sinus Straight

sinus

Tentorium cerebelli

*

Frontal crest

Crista galli

The Tentorium Cerebelli

• The tentorium cerebelli is a crescent-shaped fold of dura mater that roofs over the posterior cranial fossa.

• It covers the upper surface of the cerebellum and supports the occipital lobes of the cerebral hemispheres.

Tentorium cerebelli

Falx cerebri

The Falx Cerebelli

• The falx cerebelli is a small, sickle-shaped fold of dura mater that is attached to the internal occipital crest and projects forward between the two cerebellar hemispheres.

• Its posterior fixed margin contains the occipital sinus.

The Diaphragma Sellae

• The diaphragma sellae is a small circular fold of dura mater that forms the roof for the sella turcica.

• A small opening in its center allows passage of the stalk of the pituitary gland

Dural Nerve Supply

• Branches of the trigeminal, vagus, and first three cervical nerves and branches from the sympathetic system pass to the dura.

• The dura is sensitive to stretching, which produces the sensation of headache.

Dural Blood Supply

Dural Arterial Supply• The dura mater’s arteries

supply from the internal carotid, maxillary, ascending pharyngeal, occipital, and vertebral arteries.

• From a clinical standpoint, the most important is the middle meningeal artery, which is commonly damaged in head injuries.

Dural Venous Drainage• The meningeal veins lie in

the endosteal layer of dura. • The middle meningeal vein

follows the branches of the middle meningeal artery and drains into the pterygoid venous plexus or the sphenoparietal sinus.

• The veins lie lateral to the arteries.

Arachnoid Mater Delicate, impermeable & avascular

membrane covering the brain

Lying between Pia mater (internally) & dura Mater(externally)

Separated from dura mater by a potential space, the subdural space (filled by a film of fluid)

Separated from pia mater by the subarachnoid space (filled with CSF)

The outer and inner surfaces covered with flattened mesothelial cells


Arachnoid mater

Arachnoid mater

Arachnoid villi Arachnoid mater

Subarachnoid space

Arachnoid granulations

Subdural space

Arachnoid projects into venous sinuses

- sites for CSF diffuses into bloodstream

• Superior cerebral veins, traverse the subdural space to reach the superior sagittal sinus and its lacunae

SUBDURAL SPACE :


Subdural haematoma

*

Dura

Arachnoid

Subarachnoid Space (SP) :

Relatively narrow over the surface of cerebral hemisphere, but sometimes becomes much wider in areas at the base of the brain, the widest space is called subarachnoid cisterns

The cisterna cerebellomedularis lies between inferior surface of the cerebellum and roof of 4th ventricle

The cisterna interpeduncularis lies between 2 cerebral hemispheres. All the cisternae are in free communication with one another & with the remainder of subarachnoid space

Median sagittal section to show the subarachnoid cisterns & circulation of CSF

Superior cistern

Interpeduncular cistern

Cerebellomedullary cistern

Chiasmatic cistern

Pontine cistern

*

Subarachnoid haemorrage

Dura

Arachnoid

Pia mater

Pia Mater

• Pia Mater is a vascular membrane covered by mesothelial cells.

• Closely invests the brain, covering the gyri, descending into the deepest sulci & closely applied to the cortical surface.

Pia mater

Pia mater

Pia Mater

It extends out over the cranial nerves & fuses with their epineurium

The cerebral arteries entering the substance of the brain, carry a sheath of pia mater with them

The pia mater forms the TELA CHOROIDAE .

The tela choroidae fuse with ependyma to form the choroid plexus

Choroid plexus forms CSF

Coronal section of the interventricular foramen showing the choroid plexus of 3rd & lateral ventricles

Ependyma

Choroid plexus of 3rd ventricle

Choroid plexus of lateral ventricle

Pia mater of tela choroidae

Read About

The Venous Blood Sinuses

VENTRICLES

OBJECTIVES

• Illustrate and describe the ventricles.• Describe the structure of the ventricles.• Illustrate and describe the cerebrospinal

fluid (CSF) formation, absorption and circulation.

VENTRICLES(Ventricular System)

• A ventricle is an internal cavity of the brain. Within the brain, which is filled with cerebrospinal fluid(CSF).

• The ventricular system is composed of two lateral ventricles and two midline ventricles( third and fourth ventricles).


• The chambers are connected to allow the flow of cerebrospinal fluid via two interventricular foramen (referred to as the foramen of Monro) and the cerebral aqueduct (referred to as the aqueduct of Sylvius).

Lateral view to show the ventricular system of the CNS

Central canal of medulla oblongata & spinal cord

Fourth ventricle

Lateral ventricle

Third ventricle

Interventricular foramen (Monro)

Cerebral aqueduct


CONSISTS OF :

1) Lateral ventricle

2) Third ventricle

3) Fourth ventricle

4) Central canal of the medulla oblongata & spinal cord

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Lateral Ventricles

• The lateral ventricles are two curved shaped cavities located within the cerebrum.

• The lateral ventricles are separated by the septum pellucidum and do not communicate directly

Lateral ventricle

Frontal lobe

Parietal lobe

Temporal lobe

Occipital lobe

C-shaped cavity & may be divided into :

2. Anterior horn

1. Body

3. Posterior horn

4. Inferior horn

Third ventricle

Fourth ventricle

Lateral view of the ventricular cavities of the brain

Lateral ventricle

Anterior horn

Inferior horn

Posterior horn

Lateral view to show the ventricular system of the CNS

The third ventricle is a narrow cavity or a slitlike cleft between the 2 thalamus

Communicates ;

• Anteriorly with lateral ventricles through interventricular foramina (of monro)

• Posteriorly with fourth ventricle through cerebral aqueduct (of sylvius)

Posterior view to show the ventricular system of the CNS

Third ventricle

Frontal lobe

Parietal lobe

Temporal lobe

Occipital lobe

Third ventricle

Third ventricle

Hypothalamus

Coronal section of the brain (posterior view)

Third ventricle

Thalamus

ROOF

FLOOR

Lateral wall

Body of fornix

Fourth ventricle

• The fourth ventricle Is a rhomboid or diamond shaped cavity.

• It is a wide and flattened space located just anterior to the cerebellum and posterior to the upper, or superior, half of the medulla oblongata and the pons.

Cerebellum

Pons

Medulla oblongata (superior half)

Sagittal section of the 4th ventricle

Cerebral aqueduct

Central canal (spinal cord)

Fourth ventricle

Fourth ventricle

ANTERIORPOSTERIOR

Frontal lobe

Parietal lobe

Temporal lobe

Occipital lobe

Fourth ventricle

Pons

Medulla oblongata (superior half)

Fig. : Sagittal section of the 4th ventricle

Cerebral aqueduct

ANTERIOR

POSTERIOR

Superior part of the roof ;

Superior medullary velum

Inferior part of the roof ;

Inferior medullary velum

Roof or posterior wall of fourth ventricle :

Floor or rhomboid fossa of fourth ventricle :

Formed by ;

1. Posterior surface of the pons

2. Cranial ½ of the medulla oblongata

Medial sulcus

(divides the floor into symmetrical halves)

Medial eminence

Sulcus limitans

Facial colliculus

Stria medullaris

(strands of nerve fibers)

Hypoglossal triangle

Vagal triangle

Posterior view of the 4th ventricle

CENTRAL CANAL

Opens superiorly into the fourth ventricle

Fourth ventricle

Inferior ½ of medulla oblongata

Entire length of spinal cord

Central canal

(Lined with ependyma but no choroid plexus in the central canal)

Extends ;

Frontal lobe

Parietal lobe

Temporal lobe

Occipital lobe

CENTRAL CANAL

Conus medullaris-Terminal ventricle

CEREBROSPINAL FLUID

• It is formed by invaginating of vascular pia mater into the ventricular cavity

• It becomes highly convoluted & produce a spongy-like appearance

• It enters the 3rd and 4th ventricles through their roofs, and the lateral ventricles through the choroid fissure

• produces cerebrospinal fluid (CSF)

CHOROID PLEXUS

Lateral ventricle

Third ventricle

Fourthventricle

Coronal section of the cavities of the lateral and 3rd ventricles

Cavity Of Lateral Ventricle

Cavity Of Third Ventricle

Pia Mater

Ependyma

CN

THALAMUS

CORPUS CALLOSUM

Choroid Plexus of The Lateral Ventricle

Pia Mater of Tela Choroidae

BODY OF FORNIX

Choroid Plexus of The Third Ventricle

Blood supply derives from choroidal branches of the internal carotid & basilar arteries

Arachnoid mater

Pia mater

Ependyma

CEREBELLUMCavity of fourth ventricle

Choroid plexus of the fourth ventricle

•T shaped, vertical part is double

• Horizontal part extends into lateral recesses of each ventricle (foramina of Luskha)

• Blood supply ; posterior inferior cerebellar arteries

What is cerebrospinal fluid (CSF) ?• Clear, colorless fluid

• Produced by the choroid plexus

• Found in the :

Ventricles of the brain

Subarachnoid space (between Arachnoid + Pia mater) around the brain & spinal cord

• The pressure of the CSF is kept remarkably constant.

• Based on the Monro-Kellie doctrine :

• “Volume of BLOOD, CSF & BRAIN at any time must be relatively constant”

Physical characteristics and composition of the CSF

Appearance Clear and colourlessVolume 130 mlRate of production 0.5 ml/minPressure 60-150 mm of waterComposition protein 15-45 mg/100 ml glucose 50-85 mg/ 100 ml chloride 720-750 mg/100 mlNo. of cells 0-3 lymphocytes/cu mm

Function of the CSF :

1. Cushions & protects the CNS from trauma

2. Provides mechanical buoyancy & support for the brain

3. Serves as a reservoir & assists in the regulation of the contents of the skull

4. Nourishes the CNS

5. Removes metabolites from the CNS

6. Serves as a pathway for pineal secretions to reach the pituitary gland

Sites of formation :1. Choroid plexus of the ventricle cavities, mostly is formed

in the LATERAL VENTRICLES

2. Some originate from the ependymal cells lining the ventricles

3. Some from the brain substances through perivascular spaces

Movement of CSF inside the ventricle is controlled by the:1. Pulsation of the artery in the choroid plexus

2. By the aid of the cilia & microvilli of the ependymal cells

Choroid plexus of the 4th ventricle

Choroid plexus of the 3rd ventricle

12

3

5

3.2

3.1

4

Superiorly = lateral aspect of each cerebral hemisphere

Inferiorly = subarachnoid space around the brain & spinal cord

Choroid plexus of the lateral ventricle

cerebrospinal fluid (CSF)• The CSF is formed in the lateral

ventricles escapes by the foramen of monro into the third ventricle

• From the third ventricle by the aqueduct into the fourth ventricle.

• Then from the fourth ventricle the fluid is poured into the subarachnoid spaces through the medial foramen of majendie and the two lateral foramina of luschka.

• There is no evidence that functional communications between the cerebral ventricles and the subarachnoid spaces exist in any region except from the fourth ventricle.

Choroid plexus of the lateral ventricle

Site of formation

1. Lateral ventricle

2. Third ventricle

Interventricular foramina

3. Fourth ventricle

Cerebral aqueduct

3.2 Lateral foramina (Luschka)

3.1 Median foramen (Magendie)

3.2 Lateral foramina (Luschka)

4. Subarachnoid space

Inferiorly

Superiorly

Absorbed

Superiorly

Absorbed

Median sagittal section to show the subarachnoid cisterns & circulation of CSF

Superior cistern

Interpeduncular cistern

Cerebellomedullary cistern

Chiasmatic cistern

Pontine cistern

Circulation of CSF in subarachnoid space :

Median foramen of 4th ventricle

Factors that facilitate the flow of CSF in subarachnoid space ;

1. Pulsation of the cerebral & spinal arteries

2. Movements of the vertebral column

3. Respiration & coughing

4. Changing of the positions

Absorption of CSF into dural venous sinuses

• Main sites - arachnoid villi (project into dural venous sinuses, especially, superior sagittal sinus)

• Arachnoid villi are covered by endothelium of the venous sinus

• Arachnoid villi tend to be grouped together & form elevations known as arachnoid granulations

• CSF pressure >> the pressure in the sinus

• The rate of absorption of CSF through the arachnoid villi controls the CSF pressure

CLINICAL APPLICATION

Hydrocephalus• The term hydrocephalus is

derived from the Greek words "hydro" meaning water and "cephalus" meaning head.

• It is excessive accumulation of fluid in the brain.

BLOOD SUPPLY OF THE BRAIN

OBJECTIVES

• Illustrate and describe the formation of the circle of willis

• Describe the blood supply of the brain– Arterial supply– Venous drainage

Blood Supply of The Brain

• The brain receives it arterial supply from two pairs of vessels, the vertebral and internal carotid arteries which are interconnected in the cranial cavity to produce an arterial circle (of Willis).

Internal carotid artery

Internal Carotid Artery• Begins – bifurcation of Com Carotid A• Perforates base of skull – carotid canal• Enters middle cranial fossa beside dorsum sellae• In the cavernous sinus

– Horizontal• Emerge out – medial side of Ant clinoid process – perforates

dura & arachnoid mater – enters subarachnoid space• Turns posteriorly – below optic nerve• Turns upward – lateral to optic chiasma• Now is under anterior perforated susbtance• Divides – into ANTERIOR & MIDDLE cerebral arteries

Vertebral artery

Common carotid artery

External carotid artery

Internal carotid arteryIn temporal bone

Internal carotid artery in cavernous sinus

Basilar artery

Posterior cerebralartery

Posterior communicatingartery

Middle cerebralartery

Anterior cerebralartery

Basilar artery


Vertebral Artery• Branch of first part of subclavian A• Passes – foramen transvesarium C6 – C1• Enters through foramen magnum – perforates

dura & arachnoid mater – enters subarachnoid space

• Turns upward, forward, medially – medulla oblongata

• Lower border of pons – joins opposite side– BASILAR artery

Vertebral artery

Common carotid artery

External carotid artery

Internal carotid arteryIn temporal bone

Internal carotid artery in cavernous sinus

Basilar artery


Posterior communicatingartery

Middle cerebralartery

Anterior cerebralartery

Basilar artery


Blood Supply of The Brain• VERTEBRAL

– Basilar– Posterior cerebral

artery

• INTERNAL CAROTID– Middle cerebral– Anterior cerebral– Anterior

communicating artery

– Posterior communicating artery

CIRCLE OF WILLIS

• VERTEBRAL– Basilar– PCA– Pontine– Labyrinthine– Ant Inf CA– Sup cerebellar– Choroidal

• INTERNAL CAROTID– ACA – MCA – Ophthalmic– Ant ComA– Post Com A– Choroidal

Branches of :-

• CEREBRAL (ICA)– Ophthalmic– Post Communicating– Choroidal– Ant Cerebral

• Cortical• Central • Communicates with

– Ant Comm Art– Post Cerebral

– Mid Cerebral• Cortical• Central

• CRANIAL (VERT)– Meningeal– Post Spinal– Ant Spinal– Post Inf Cerebellar– Medullary

• (BASILAR)– Pontine– Labyrinthine– Ant Inf Cerebellar– Sup Cerebellar– Post Cerebral

• Cortical• Central • Choroidal

Circle of Willis

• Interpeduncular fossa – base of brain

• Anastomosis – 2 internal carotid

arteries– 2 vertebral arteries

• In the subarachnoid space

INFERIOR VIEW

Vertebral arteries

Basilar A

Posterior cerebral artery

Posterior communicating artery

Internal carotidartery

Middle cerebral artery

Anterior cerebral artery

Anterior communicating artery

Post Inf cerebellar A

Sup cerebellar A

Ant Inf cerebellar A





Superior frontal gyrus

Central sulcus

Parieto-occipitalsulcus

Frontal pole

Superior parietal lobule

Frontal pole

ANTERIOR CEREBRAL ARTERYLOBE AREA

FRONTAL LOBE

Motor – lower limb and perineum - pericentral lobule

PARIETAL LOBE

Sensory – lower limb and perineum - paracentral lobule

Lentiform nucleus

Caudate nucleus

Internal capsule (ANT)

Hypothalamus (ANT)

lentiform

caudate

Internalcapsule

Anterior cerebral artery & anterior communicating artery


Central branches

Temporal pole

Left middle cerebral artery

Right middle cerebral artery

Medialstriatearteries

Lateralstriatearteries

Central branches

MIDDLE CEREBRAL ARTERYLOBE AREA

FRONTAL Motor – except for paracentral lobule

Motor speech – esp left side

PARIETAL Sensory – except for paracentral lobule

Sensory speech

TEMPORAL Auditory

Lentiform nucleus

Caudate nucleus

Internal capsule (ANT & POST)

lentiform

caudate

Internalcapsule

Middle cerebral artery & anterior choroidal artery


Inferior temporal gyrus

Inferior temporal gyrus

POSTERIOR CEREBRAL ARTERYLOBE AREA

OCCIPITAL Visual

TEMPORAL Olfactory

Hypothalamus

Thalamus (ANT)

Cerebral pedunclethalamus

Cerebralpeduncle

Internalcapsule

Posterior cerebral artery & posterior communicating artery

Thalamus (POST)

Geniculate bodies

Cerebral pedunclethalamus

Cerebralpeduncle

Posterior lateral arteries

Lateral Geniculatebodies

Corpus striatum Middle & lateral striate

Anterior & Middle cerebral arteryInternal capsule

Thalamus PComA, basilar, PCA

Midbrain PCA, supCerebellarA, basilar

Pons Basilar, Ant, inf, supCerebellarA,

Medulla oblongata

Vertebral, ASA,PSA,PICA, basilar

Cerebellum supCerebellar, AICA,PICA

ARTERIES to specific brain areas

VENOUS DRAINAGE of THE BRAIN

• EXTERNAL– Superior

cerebral– Superficial

middle cerebral

– Deep middle cerebral

• INTERNAL– Thalamostriate

– choroidal

• SPECIFIC– Midbrain– Pons– Medulla

oblongata– cerebellum

Superior cerebral

SuperficialMiddlecerebral

basal

SuperiorSagittalsinus

Transverse sinus


InferiorSagittalsinus

Great cerebral

Internal cerebral

Straight sinus

Occipital sinus

Superior cerebral

SuperficialMiddle cerebral


Transverse sinus

Superior anastomotic V

Inferior anastomotic V

basal


InferiorSagittalsinus

Great cerebral

Internal cerebral

Straight sinus

Occipital sinus

Site of junction with transversesinus

EXTERNAL CEREBRAL VEINVEIN AREA DRAINS INTO

Superior cerebral Lateral surface of

cerebral hemisphere


Superficial middle cerebral

Cavernous sinus

Deep middle cerebral

Insula Joined by ant cerebral & striate-basal vein

Sup anas V Superior sagittal sinus

Inf anas V Inferior sagittal sinus

INTERNAL CEREBRAL VEINVEIN AREA DRAINS INTO

Thalamostriate Basal ganglia, thalamus, internal capsule,Tela choroidae of 3rd ventricle,hippocampus

Internal cerebral vein - great cerebral vein – straight sinus

DURAL VENOUS SINUS

Choroidal

VEIN of specific areas

Midbrain Basal, great cerebral

Pons Basal, cerebellar

Medulla oblongata Anterior & posterior spinal

Cerebellum Great cerebral


Inferior sagittal sinus

Straight sinus

Superior cerebral vein

Medial aspect of hemisphere

Great cerebral vein

Transverse sinus

(R & L)

Sigmoid sinus (R & L)

Confluence of sinus

IntJugular vein

IntJugular vein

Cavernous sinus

Middle cerebral vein

Inferior petrosal sinus

Superior petrosal sinus

Falx cerebriSuperior sagittal sinusInferior sagittal sinus

Straight sinus

Tentorium cerebelli

*

Superior petrosal sinus


Sigmoid sinus

Confluence of sinus

Transverse sinus

Straight sinus Transverse

sinus

Sigmoid sinus

Confluence of sinus

Jugular foramen

Cavernous sinusSuperior petrosal sinus


Superiorsagittal sinus

Cavernous sinus

• Lateral to body of sphenoid bone• Connected to opposite – intercavernous S• Receives blood

– Middle cerebral V

• Drains into– Int Jugular V –via Inf petrosal sinus– Transverse S – via Sup petrosal S

• Dural Venous sinuses – emissary veins – extracranial V

• Stroke or cerebrovascular accident:-– Blockage in the artery – cerebral infarction

• Carotid artery• Basilar artery

– Bleeding within the brain – intracerebral haemorrhage

• Aneurysm• Subarachnoid haemorrhage• Intracerebral haemorrhage - hypertension

– Damages one side of the body - contralateral

CLINICAL APPLICATION

CVA – due to blockage

CVA – due to haemorrhage

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Anatomy of meninges, ventricles, cerebrospinal fluid