Ventricles of brainThese are cavities in the brain lined by ependyma and filled with CSF. They contain choroid plexuses which 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. 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 (Magendie) and two lateral (Luschka) foramina. .
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 divisible into four parts:-
- 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 corpus callosum.
- Floor: Formed form lateral to medial by 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 fonix.
- Anterior horn: It lies in front of 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 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 fonix.
- 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 boundaries are :-
- Floor and medial wall: Bulb of posterior horn raised by forceps major and calcar avis, an elevation raised by calcarine sulcus (anterior part).
- Roof and lateral wall: Tapetum
- Inferior horn: It is the largest horn and extends into temporal lobe. It has choroid plexus. Its boundaries are :-
- Roof and lateral wall: Tapetum, tail of caudate nucleus, stria terminalis and amygdaloid body.
- Floor: Collateral eminence (elevation by collateral sulcus) and hippocampus medially.
- Third ventricle is a midline cavity of diencephalon. It is a median cleft between two thalami. Anterosuperiorly it communicates with lateral ventricle through the interventricular foramen (foramen of Monro). Posteroinferiorly it communicates with fourth ventricle through cerebral aqueduct (Duct of Sylvius). There are four extensions (recesses) of third ventricle: (a) Suprapineal recess, (b) Pineal recess, (c) Infundibular recess, and (d) Optic recess.
- Boundaries of third ventricle are:-
- Anterior wall: Lamina terminal, anterior commissure, anterior columns of fornix.
- Posterior wall: Pineal body, posterior commissure, cerebral aqueduct.
- Roof: Ependymal lining of under surface of tela choroidea of 3rd ventricle. The choroid plexus of third ventricle projects downwards from roof
- Floor: Optic chiasma, tuber cinereum, Infundibulum (pituitary stalk), mammillary body, posterior perforated substance and tegmentum of midbrain. Optic recess is seen at the junction of floor with anterior wall.
- Lateral wall: Medial surface of thalamus, hypothalamus and hypothalamic nuclei. Interventricular foramen (of Monro) is seen at the junction of roof with anterior and lateral wall.
- Interthalamic adhesion connects medial surface of two thalami. Thalamus forms the lateral wall of 3rd ventricle. Thus, interthalamic adhesion connects lateral walls of3rd ventricle.
- Habenular stria lies at the junction of roof and lateral wall. Two striae join posteriorly at habenular commissure.
- Anterior columns of fornix run backward from anterior wall and sink into lateral wall to reach mammillary body.
It is the cavity of hindbrain (rhombencephalon) lying between cerebellum (posteriorly), and pons and medulla (anteriorly). Superiorly it communicates with 3rd ventricle through cerebral aqueduct (aqueduct of Sylvius).
Inferiorly it communicates with central canal through a median (magendie) and two lateral (Luschka) foramina. It has lateral boundaries, floor, roof and a cavity.
Superolaterally It is formed by superior cerebellar peduncle. Inferolaterally it is formed by gracile and cuneate tubercles, and inferior cerebellar peduncles.
Upper part is formed by convergence of superior cerebellar peduncles and superior medullary velum. Lower part is formed by ependyma of 4th ventricle and piamater of tela choroidea of 4th ventricle, and inferior medullary velum. Roof possesses a pair of choroid plexuses.
Floor (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 4th ventricle are:-
- Median sulcus (a midline groove) divides the floor into two symmetrical halves.
- Medial eminence is present an each side of median sulcus. It presents facial colliculus formed by genu (recurring fibers) of facial nerve looping around abducent nucleus. Facial colliculus lies in pons (i.e. in pontine part of floor).
- 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).
- Vestibular area overlies vestibular nuclei, partly in pons and partly in medulla.
- Sulcus coeruleus, a bluish area due to presence of pigmented neurons containing substantia ferruginea.
- Superior and inferior fovea.