Ventricular system

Ans.A. 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. 

The fourth ventricle is the last ventricle in the cerebellum, its T shaped roof has three apertures that communicate with the subarachnoid space.

Foramen of magendi a median aperture is present dorsally in the roof, it communicates with the cisterna magna.

Foramen of luschka is a lateral aperture that is present on the 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.

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

• Upper part: Fascial colliculus on the dorsal surface of the pons.
• Intermediate part: Vestibular nuclei medullary 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 foramina (foramen of Lushka): one in each lateral recess.

B i.e. Occulomotor Nerve 

A i.e., Rhomboid fossa forms the floor

D i.e., None

Ans.B i.e., Connects III ventricle to IV ventricle

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

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

– Its length is about 18-20mm

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.

Ans. (D) Corpus callosum

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

Lateral ventricle

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

It is divisible into four parts:

1) The 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-

Roof: Formed by the corpus callosum.

Floor: Formed from lateral to medial by the caudate nucleus (body), stria terminalis, thalamostriate vein, and lateral part of upper surface of thalamus.

Medial wall (partition between two lateral ventricles): By septum pellucidum and body of fornix.

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

• 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 and upper surface of the rostrum of the corpus callosum.
• Medial (partition): Septum pellucidum and column of the fornix.

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

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

Ans. (A) Ependymocytes

Ventricles of the 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 that secrete CSF.

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

1. Two lateral ventricles (right and left),
2. Third ventricle, and
3. Fourth ventricle. o The lateral ventricle communicates with the third ventricle by interventricular foramen (foramen of Monro).
4. The third ventricle communicates with the fourth ventricle by cerebral aqueduct (aqueduct of Sylvius).
5. The fourth ventricle communicates with subarachnoid space by a median foramen (Mangendie) and two lateral (Luschka) foramina.