VENTRICLES OF BRAIN

The brain has a series of ventricles that hold CSF (Cerebrospinal Fluid).

CSF is created by the choroid plexus and circulates through the ventricles until it is absorbed by the arachnoid layer.

CSF seems to�1. act as a fluid cushion for the brain�2. transports some substances into/out of the brain.�3. maintains pressure around the brain.

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• The brain is bathed by the cerebrospinal fluid (CSF)�Inside the brain, there are spaces (ventricles) filled with CSF�There are 4 ventricles
• 2 lateral ventricles are in the brain hemispheres�3^rd ventricle is in the diencephalon�4^th ventricle is between the pons, medulla and the cerebellum.

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They are connected by�• The Foramen of Monro (lateral -> third),�• Cerebral aqueduct (third -> fourth), and�• The foramen of Magendie and Luschka�(fourth -> subarachnoid space/cisterna magna).

LATERAL VENTRICLE

Features-�The lateral ventricles are two irregular cavities situated one in each cerebral hemisphere.

Each lateral ventricle communicates with the third ventricle through an interventricular foramen (foramen of Monro).

Each lateral ventricle consists of�1 A central part.�2 Three horns: Anterior, posterior and inferior.

CENTRAL PART

This part of the lateral ventricle extends from the interventricular foramen in front to the splenium of the corpus callosum behind.

Boundaries –

• Roof-

Formed by the undersurface of the Corpus Callosum

• Medial wall-
• Septum Pellucidum
• Body of Fornix

• Floor-
• Body of Caudate nucleus
• Stria terminalis
• Thalamostriate vein
• Lateral portion of the upper surface of the thalamus
• Choroid plexus
• Upper surface of symmetric half of body of fornix

ANTERIOR HORN

Part of lateral ventricle which lie in fn front of the interventricular foramen and extend into the frontal lobe.

Boundaries-

• Anterior –

Posterior surface of genu and rostrum of the corpus callosum.

• Roof-

Anterior part of the trunk of the corpus callosum .

• Floor –
• Head of the caudate nucleus .
• Upper surface of the rostrum of the corpus callosum .

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• Medial
• Septum Pellucidum
• Column of fornix

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POSTERIOR HORN

Part of lateral ventricle which lie behind the Selenium of the corpus callosum and extend into the occipital lobe . Directed backward and medially.

Boundaries-

Floor and medially wall-

1. Bulb of the posterior horn raised by the forceps major.
2. Calcar Avis raised by the anterior part of the calcarine sulcus.

Roof and lateral wall-

Tapetum fibres of optic radiation.

INFERIOR HORN

Largest horn of lateral ventricle. It begins at the junction of the central part with the posterior horn of the lateral ventricle and extend into the temporal lobe.

Boundaries-

Roof and lateral wall-

1. Chiefly the tapetum
2. Tail of caudate nucleus
3. Stria terminalis
4. Amygdaloid body

Floor -

1. Collateral eminence raised by the collateral sulcus
2. Hippocampus medially.

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CHOROID FISSURE

The line along which the choroid plexus invaginates into the lateranarrow ricle is called Choroid fissure.

It is a C shaped slit in the medial wall of the cerebral hemisphere .

It starts at the interventricular foramen and passes around the thalamus and cerebral peduncle to the uncus .This it is present only in relation to the central part and inferior Horn of the lateral ventricle.

It’s convex margin is bounded by the fornix,the fimbria and the hippocampus and the concave margin is bounded by the thalamus,the tail of the caudate nucleus and the stria terminalis.

At the fissure,the pia matter and ependymal come into contact with each other and both are invaginated into the ventricle by the Choroid plexus.

In the central part of lateral ventricle ,the choroid fissure is a narrow gap between the edge of the fornix and the upper surface of the thalamus.

THIRD VENTRICLE

The third ventricle is a median cleft between the two thalami. Developmentally, it represents the cavity of the diencephalon, except for the area in front of the interventricular foramen which is derived from the median part of the telencephalon. The cavity is lined by ependyma

Communication –

Anterosuperiorly, on each side, it communicates with the lateral ventricle through the interventricular foramen (foramen of Monro). This foramen is bounded anteriorly by the column of the fornix, and posteriorly by the tubercle of the thalamus.

Posteroinferiorly, in the median plane, it communicates with the fourth ventricle through the cerebral aqueduct .

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• Recesses-

Recesses are extension of the cavity. These are-

1. Suprapineal
2. Pineal-upper lamina of the recess is traversed by habenular commissure and lower lamina by the posterior commissure.
3. Infundibular (Latin funnel).�Optic � Vulva-between the diverging

columns of fornix.

Boundaries-

Anterior wall

1. Lamina terminalis.� Anterior commissure.� Anterior columns of fornix. The two columns of the fornix diverge, pass downwards and backwards, and sink into the lateral wall of the third ventricle to reach the mammillary body.

Posterior wall-

1. Pineal body�Posterior commissure (in the lower lamina of the pineal stalk).� Cerebral aqueduct.

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Roof-

It is formed by body of fornix and the ependyma lining the under surface of the tela choroidea of the third ventricle. The choroid plexus of the third ventricle projects downwards from the roof.�At the junction of the roof with the anterior and lateral walls, there are the interventricular foramina.

Floor-

It is formed by hypothalamic structures:

1. Optic chiasma.� Tubercinerium.�Infundibulum (pituitary stalk).�Mammillary bodies.�Posterior perforated substance.�Tegmentum of the midbrain.

Lateral wall-

It is formed by the following:

1. Medial surface of thalamus (in its posterosuperior part).�Hypothalamus (in its anteroinferior part).�The hypothalamic sulcus which separates the thalamus from the hypothalamus. The sulcus extends from the interventricular foramen to the cerebral aqueduct.

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FOURTH VENTRICLE

The cavity of hindbrain is called the fourth ventricle.

It is a tent-shaped space situated between the pons and upper part of medulla oblongata in front and cerebellum behind.

So it lies dorsal to pons and upper part of medulla oblongata and ventral to cerebellum.

It has lateral boundaries, floor, roof and a cavity

Lateral Boundaries-

On each side, fourth ventricle is bounded :

1. Inferolaterally by gracile, cuneate tubercles and inferior cerebellar peduncles.�Superolaterally by the superior cerebellar peduncles

Floor –

It is also called ‘rhomboid fossa’ because of its rhomboidal shape. The floor is formed by:

1. Posterior (dorsal) surface of lower or closed part of pons
2. Posterior (dorsal) surface of open or upper part of medulla oblongata.

Structural layers –

The floor is lined by

1. Ependyma.� A thin layer of the neuroglia beneath the ependyma.� A layer of grey matter, forming the various nuclei deep to neuroglia.

Parts-

It is divisible into :

1. An upper triangular part formed by dorsal surface of pons
2. A lower triangular part formed by dorsal surface of medulla.� The intermediate part is at the junction of pons and medulla. This part is marked by transversely running fibres which are fibres of Stria medullaris. These fibres represent fibres from arcuate nucleus to the opposite cerebellum.

Features of the Floor-

1. Dorsal median sulcus divides the floor into two symmetrical halves .� The sulcus limitans presents depression at the cranial end called superior fovea and towards caudal part called inferior fovea.

3 .Medial eminence: The eminence is wider above and narrow below. It presents facial colliculus just opposite and medial to superior fovea.� 4 .In the uppermost part (pontine part) the sulcus limitans overlies an area that is bluish in colour and is called locus coeruleus.

5 .Descending from the inferior fovea, there is a sulcus that runs obliquely towards midline. This sulcus divides medial eminence into two triangles.�6 .Between the vagal triangle above and gracile tubercle below there is small area called the area postrema which may function as chemoreceptor. �7 .Vestibular area: This lies lateral to the inferior fovea (sulcus limitans) which overlies the vestibular nuclei.

Roof –

• The roof of the ventricle is diamond-shaped and can be divided into superior and inferior parts .
• The superior or cranial part of roof is formed by superior cerebellar peduncles and superior medullary velum.
• The superior cerebellar peduncles on emerging from central white matter of cerebellum pass first cranially and ventrally forming at first lateral boundaries of ventricles.
• On approaching the inferior colliculi, they converge and then intermingle over the ventricles and form part of the roof.
• The superior medullary velum which is made up of nervous tissue fills the angular interval between the two superior cerebellar peduncles. It is covered on the dorsal surface by lingula of superior vermis.

TELA CHOROIDEA OF FOURTH VENTRICLE

• It is a double layer of pia matter which occupies the interval between the Cerebellum and the lower part of the ventricle
• The tela Choroidea with vascular fringes covered by secretory ependyma form the choroid plexus of fourth ventricle.
• The vertical limb of two plexuses lie side by side so that whole structure is T shaped.
• The arterial supply of these plexuses is from the posterior inferior cerebellar arteries

Communication-

Inferiorly – Central canal

Superiorly- Cerebral aqueduct

Opening in the roof –

Foramen of Magendie – Communication between ventricular system and subarachnoid space.

Foramina of Luschka – Fourth ventricle communicate with subarachnoid space.

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• Angles-

Superior angle: Continuous with cerebral aqueduct.�Inferior angle: Continuous below with central canal of spinal cord.�Lateral angles: One on each side towards the inferior cerebellar peduncles.

Recesses of fourth Ventricle :

• Two lateral recesses one on each side.
• One recess present in the median plane is known as Median dorsal recess.
• Two lateral dorsal recesses one on each side.

CLINICAL ANATOMY

Hydrocephalus –

Hydrocephalus is an abnormal increase in the volume of the cerebrospinal fluid within the skull.

Causes can be:�1. Blockage of the circulation of cerebrospinal

fluid.�2. Diminished absorption of cerebrospinal fluid.�3. Excessive formation of cerebrospinal fluid.

Infratentorial Brain Tumour-

Block the Foramina of Luschka and Magendie situated

in the roof of fourth ventricle.

This results in marked early rise of intracranial

pressure which causes headache, vomiting,

papillodema etc.

Other issues -

• The third ventricle is a narrow space which is easily obstructed by local brain tumours or by developmental defects. The obstruction leads to raised intracranial pressure in adults and hydrocephalus in infants.�Tumours in the lower part of the third ventricle give rise to hypothalamic symptoms, like diabetes insipidus, obesity, sexual disturbance, disturbance of sleep, hyperglycaemia and glycosuria.
• The site of obstruction can be found out by CT scan/MRI (magnetic resonance imaging) scans, where, the third ventricle is seen, normally, as a narrow, vertical midline shadow.

RESEARCH PAPER ON VENTRICLE OF BRAIN

Brain ventricular system and Cerebrospinal fluid development and functions –

Abstract -

The brain ventricular system is a series of connected cavities, filled with cerebrospinal fluid (CSF), that forms within the vertebrate central nervous system (CNS). The hollow neural tube is a hallmark of the chordate CNS, and a closed neural tube is essential for normal development. Development and function of the ventricular system is examined, emphasizing three interdigitating components that form a functional system: ventricle walls, CSF fluid properties, and activity of CSF constituent factors. The cellular lining of the ventricle both can produce and is responsive to CSF. Fluid properties and conserved CSF components contribute to normal CNS development.

Anomalies of the CSF/ventricular system serve as diagnostics and may cause CNS disorders, further highlighting their importance. This review focuses on the evolution and development of the brain ventricular system, associated function, and connected pathologies. It is geared as an introduction for scholars with little background in the field.

Citation –

Fame, R. M., Cortés-Campos, C., & Sive, H. L. (2020). Brain ventricular system and cerebrospinal fluid development and function: light at the end of the tube: a primer with latest insights. BioEssays, 42(3), 1900186.