Ventricular system of brain

Dr. Syed Imad

FCPS, MRCS

VENTRICULAR SYSTEM

What are the ventricles ?

How do they develop ?

What do they contain ?

VENTRICULAR SYSTEM

Communicating system of cavities

Cavity of neural tube that persists

Ependyma, a single epithelial-like layer of cells.

Cerebrospinal fluid (CSF)

Neural tube

VENTRICULAR SYSTEM

VENTRICULAR SYSTEM

Comprises of:

two lateral ventricles

the third ventricle

the cerebral aqueduct

and the fourth ventricle

VENTRICULAR SYSTEMfrom the right from above

Central canal

VENTRICULAR SYSTEM

Is CSF stagnant or it circulates ? What is the path of CSF flow ? Where does it come from ? Where does it go ?

VENTRICULAR SYSTEM

Interventricular foramen (of Monro) --- leads from the lateral into the third ventricle.

Ventricles communicate with subarachnoid spaces and cisterns via apertures of the fourth ventricle.

External CSF circulation Internal CSF circulation

Interventricular foramen

3rd Ventricle

Choroid plexus

Venous Sinus Lateral ventricle

Subarachnoid space

Subarachnoid space and cisterns

Choroid Plexus

The lining ependyma of each ventricle comes into contact with the surface pia mater allowing the invagination of a mass of blood capillaries --- combination of these capillaries, pia and ependyma constitutes the choroid plexus.

Choroid Plexus lateral ventricles

continuous through Interventricular foramen with the small plexus in the third ventricle.

secretes the bulk of the CSF

fourth ventricle

separate from that in the third and lateral ventricles

only makes a small contribution to the total amount of CSF

CSF CSF is clear, colorless, and odorless fluid

produced within the ventricles secreted by the Choroid plexus

provides mechanical support – protection from pressure changes.

In adults, the total volume of CSF is about 150 ml

Between 400 and 500 mL of CSF is produced and reabsorbed daily.

CSF Flow

MENINGES & SPACES

VENOUS SINUSES OF THE DURA MATER

Venous sinuses are network of channels that receive all the venous blood from the brain

Venous sinuses lie b/w the inner and outer layers of the dura ---- Inferior sagittal and straight sinuses are the exceptions

Arachnoid granulations also project into the venous sinuses to return CSF to the bloodstream

Dural venous sinuses

Lateral ventricles

Central canal

Lateral ventricles

C-shaped cavity

within each cerebral hemisphere

Consists of:

anterior horn - frontal lobe

body --- parietal lobe

posterior horn ---- occipital lobe

inferior horn ---- temporal lobe

Lateral ventricles

Anterior horn and Body:

Roof: Corpus callosum and the fornix

Medial surface: Septum pellucidum (thin partition between the fornix and

corpus callosum)

Thalamus and Basal ganglia

Brain stem

Thalamus

Thalamus and Basal ganglia

Brain stem

Amygdaloid body

Thalamus

Tail of Caudate nucleus

Head of Caudate nucleusLentiform nucleus Body of Caudate nucleus

Lateral ventricles

Anterior horn and Body:

Floor:Caudate nucleus, thalamus

Fibers of Internal capsule

Corpus callosum

Left thalamus and basal nuclei, viewed from behind

Lateral ventricles

Posterior horn

is the most variably developed and may even be absent.

Lateral ventricles

Cingulate sulcus

Posterior horn of lateral ventricle

Collateral eminence

Collateral sulcus

Splenium of

corpus callosumTapetum of corpus

callosum

Optic radiation

Callosal radiation

Lateral ventriclesPosterior Horn Roof and lateral wall

Tapetum of the corpus callosum Optic radiation lying against the tapetum in the lateral wall.

Medial wall --- two convexities:

Upper (bulb of the posterior horn) Splenium of the corpus callosum

Lower (Calcar avis) Calcarine sulcus. If Calcar avis is well developed, it obliterates the posterior horn.

Floor Collateral eminence, produced by the collateral sulcus

Lateral ventriclesInferior horn -- Largest horn

Lateral ventriclesInferior Horn

Floor medially

hippocampus laterally

collateral eminence

Roof tail of the caudate nucleus, amygdaloid body

Lateral wall Tapetum of corpus callosum

Lateral ventriclesConvexities within Lateral ventricles: The grey matter at the bottom of a sulci indents the cavity Such sulci are

Parahippocampal Calcarine Collateral

Caudate nucleus and thalamus also project into the cavity

Elsewhere the walls of the cavity are formed by white matter of the cerebral hemisphere

Third Ventricle

Cavity within Diencephalon

slit-like space, lying in the sagittal plane

Neural tube

Third Ventricle

Comprises of:

Anterior wall

Two side walls

Floor

Roof

Third Ventricle

Third Ventricle

Third Ventricle Anterior wall:

lamina terminalis anterior commissure

Floor: optic chiasma tuber cinereum median eminence infundibulum mamillary bodies posterior perforated substance tegmentum of the cerebral peduncles

Two side walls:

Thalamus Interthalamic adhesion (60% of brains)

Hypothalamus Supraoptic nucleus – ADHParaventricular nucleus – Vasopressin/Oxytocin

Subthalamus Subthalamic nucleus

Tuber cinerum

Median eminence

Infundibulum

Posterior pitutary

Third Ventricle

Aqueduct (of Sylvius)

Cavity within midbrain

Continuous above with third ventricle

leads through the midbrain into the cavity of the fourth ventricle

Choroid fissure

C-shaped slit in the medial wall of the cerebral hemisphere

convexity – fornix

concavity – thalamus, tail of the caudate nucleus

Invaginated by choroid plexus of lateral ventricle

Tela choroidea (double fold of pia)

Pitutary stalk (solid)Infundibulum (hollow)

Tela choroidea

Reflection of two layers of pia matter

Medially b/w interventricular foramina

Laterally across the upper surface of thalamus

Fourth ventricle

Blood-Brain Barrier

Collectively, the blood vessels within the brain have a very large surface area that promotes the exchange of oxygen, carbon dioxide, amino acids, and sugars between blood and brain.

The blood-CSF barrier is formed by active transport from the blood vessels to the brain- Epithelial cells of joined by tight junctions, form a continuous layer that selectively permits the passage of some substances but not others.

Why do we need this?

no blood/brain barriercorpora amylacea --- calcify ---- after the age of forty years they normally throw a shadow in radiographs of the skull displaced calcified pineal indicates a space-occupying lesion above the tentoriummelatonin (a hormone related to serotonin), which in animals and probably in man also has an antigonadotrophic action.

part of the tuber cinereum at the base of the infundibulum is the median eminence — highly important as the site of the neurosecretory cells that control the anterior pituitary, and one of the few regions with no blood/brain barrier

Clinical correlates

Hydrocephalous Arnold Chiari malformation Intraventricular hemorrhage Ependymal tumors Subarachnoid hemorrhage