Ventricular system

Trigone of lateral ventricle

Trigone of the lateral ventricle is a triangular prominence of the floor of the lateral ventricle at the transition between occipital (posterior) and temporal (anterior) horn

The lateral ventricles connect to the central third ventricle through the interventricular foramen of Monro.

Foramen of munro

The median aperture (“Foramen of Magendie”) drains CSF from the fourth ventricle into the cisterna magna. Cisterna magna occupies the interval between inferior surface of cerebellum and posterior aspect of medulla oblongata.

The two lateral apertures (foramina of Luschka), one on the left and one on the right, are the primary routes for drainage of cerebrospinal fluid from the fourth ventricle into the cerebellopontine angle cistern. The foramen on axial images is posterior to the pons and anterior to the caudal cerebellum.

The lateral ventricle comprises a cavity within the telencephalon. It is divided into anterior horn, body, a posterior horn and an inferior horn. The junction between the body of lateral ventricle and its posterior and inferior horn is known as the atrium or collateral trigone. 

• Bodies of the lateral ventricle are separated by paired septi pellucidi.
• Choroid plexus of the lateral ventricle is located anteromedially in the body and superomedially in the temporal horn. The anterior horn and posterior horn do not contain elements of the choroid plexus.
• Lateral ventricle communicate with the third ventricle via the paired foramina of Monro at the junction of anterior horn and body of the lateral ventricle inferiorly. 

Fourth ventricle is the last ventricle in the cerebellum, its T shaped roof has three apertures which communicates with the subarachonoid space. Foramen of magendi a median aperture is present doraslly in the roof, it communicates with the cisterna magna. Foramen of luschka is a lateral aperture which is present on right and left side. It drains into the cerebellopontine angle cistern.

Lateral ventricle develops from the cavity of telencephalon. Third ventricle develops from diencephalon. Cavity of mesencephalon remains narrow and forms the aqueduct, while the cavity of rhombencephalon forms the fourth ventricle.

The two interventricular foramens, or foramens of Monro, are apertures between the column of the fornix and the anterior end of the thalamus. The two lateral ventricles communicate with the third ventricle through these foramens and drainage of CSF occurs.

• Upper portion of roof: The superior peduncle and the anterior medullary velum; 
• Lower portion of roof: The posterior medullary velum, the epithelial lining of the ventricle covered by the tela chorioidea inferior and the taeniae of the fourth ventricle.

• Upper part :Fascial colliculus on the dorsal surface of pons.
• Intermediate part:Vestibular nuclei medulllary striae.
• Lower part:Upper part of medulla oblongata containing hypoglossal and vagal triangles.

• One median foramen (foramen of Magendie): in the lower part of the inferior medullary velum.
• Two lateral foramens (foramens of Lushka): one in each lateral recess.

B i.e. Occulomotor Nerve 

A i.e., Rhomboid fossa forms the floor

D i.e., None

B i.e., Connects HI ventricle to IV ventricle

– Rhomboid fossa or floor of 4^th ventricle has abducent motor nucleus, dorsal motor nucleus of vagus, hypoglossal nucleus, and facial nucleus.

– 4^th ventricle communicates through cerebral aqueduct of sylvius with 3^rd ventricle.

A i.e. Choroid plexus

Ans. is `d’ i.e., Both lateral and third ventricle

o CSF is produced by choroid plexus in the lateral and III ventricles. Then it flows through the aqueduct ofsylvius into the 4^th ventricle and from there into the subarachnoid space to be absorbed by the arachnoid villi.

o Obviously any obstruction in the aqueduct of sylvius will lead to enlargement of the proximal ventricles (i.e. both lateral and HP’ ventricles).

Floor of 4th ventricle (Rhomboid fossa)

• It is diamond or rhomboidal shaped and is formed by posterior surface of pons (upper triangular part or pontine part) and dorsal surface of medulla (lower triangular part or medullary part) junction of pons and medulla forms intermediate part. Features of 4^th ventricle are :‑

1. Median sulcus (a midline groove) divides the floor into two symmetrical halves.
2. Medial eminence is present an each side of median sulcus. It presents facial colliculus formed by genu (recurving fibers) of facial nerve looping around abducent nucleus. Facial colliculus lies in pons (i.e. in pontine part of floor).
3. Hypoglossal triangle overlying hypoglossal nucleus and vagal triangle overlying dorsal nucleus of vagus. Both of these triangle lie in the medulla (medullary part of floor).
4. Vestibular area overlies vestibular nuclei, partly in pons and partly in medulla.
5. Sulcus coeruleus, a bluish area due to presence of pigmented neurons containing substantia ferruginea.
6. Superior and inferior favea.

Anterior horn of lateral ventricle is closed anteriorly by the genu and rostrum of corpus callosum.

Lateral ventricle

Two lateral ventricles are the cavities of cerebral hemisphere (one in each hemisphere). Each lateral ventricle communicates with third ventricle through interventricular foramen of Monro.

It is divisile into four parts :‑

1) Central part (body) : It is located in the medial parts of frontal and parietal lobes. It extends from interventricular foramen (of Monro) in front to splenium of corpus callosum behind. It has choroid plexus. It has :- o Roof : Formed by corpus callosum.

1. Floor : Formed form lateral to medial by caudate nucleus (body), stria terminalis, thalamostriate vein, and lateral part of upper surface of thalamus.
2. Medial wall (partition between two lateral ventricles) : By septum pellucidum and body of fornix.

2) Anterior horn : It lies in front of interventricular foramen of Monro extending into the frontal lobe. It has no choroid plexus. Its bondries are :-

• Anterior : Posterior surface of genu and rostrum of corpus callosum.
• Roof : Anterior part of trunk of corpus callosum.
• Floor : Head of caudate nucleus and upper surface of rostrum of corpus callosum.
• Medial (partition) : Septum pellucidum and column of fornix.

3) Posterior horn : It lies behind splenium of corpus callosum and extends into occipital lobe. It may be variable in size (may be absent). It has no choroid plexus. Its boundries are :-

1. Floor and medial wall : Bulb of posterior horn raised by forceps major and calcar avis, an elevation raised by calcarine sulcus (anterior part).
2. Roof and lateral wall : Tapetum

4) Inferior horn : It is the largest horn and extends into temporal lobe. It has choroid plexus. Its boundries are

1. Roof and lateral wall : Tapetum, tail of caudate nucleus, stria terminalis and amygdaloid body.
2. Floor : Collateral eminence (elevation by collateral sulcus) and hippocampus medially.

Ventricles of brain are lined by ependyma (ependymocytes).

Ventricles of brain

These are cavities in the brain lined by ependyma and filled with CSF.

They contain choroid plexuses wich secrete CSF.

These are four fluid filled intercommunicating cavities within the brain :-

i) Two lateral ventricles (right and left),

ii) Third ventricle, and

iii) Fourth ventricle. o Lateral ventricle communicates with third ventricle by interventricular foramen (foramen of Monro).

Third ventricle communicates with fourth ventricle by cerebral aqueduct (aqueduct of sylvius).

Fourth ventricle communicates with subarachnoid space by a median foramen (Mangendie) and two lateral (Luschka) foramina.