VENTRICULAR SYSTEM ON THE BRAIN
The cerebral ventricles are interconnected spaces in the brain that produce the cerebrospinal fluid and transport it all over the cranial cavity. They are lined by the ependymal cells, which forms the choroid plexus. The choroid plexus produce the cerebrospinal fluid. The ventricular system consists of the two lateral ventricles, third ventricle, fourth ventricle and central aqueduct.
The structures of the ventricular system are embryologically developed from the neural tube, at its neural canal. It develops as part of the primitive neural tube that will develop into the brainstem. The neural canal expands laterally and dorsally creating the fourth ventricle. The neural canal that does not expand nor change level forms the cerebral aqueduct. The forth ventricle narrows in the caudal medulla at the obex to become the central spinal cord.
By the fourth week of embryological development, there are swellings that form in the embryo, near where the head will develop. These swellings are prosencephalon, mesencephalon and rhombencephalon, these further divides into five sections.
The prosencephalon divides into telencephalon that forms the cortex of the brain, and diencephalon. The ventricles within the telencephalon become the lateral ventricles and the ventricles within the diencephalon become the third ventricle. The Rhombencephalon divides into the myelencephalon and metencephalon. The ventricles within the rhombencephalon become the fourth ventricles and the ventricles within the mesencephalon become the aqueduct of sylvius (central aqueduct).
1. LEFT AND RIGHT LATERAL VENTRICLES
These are located within the left and right cerebral hemisphere respectively. Consists of central part, which lies within the parietal lobe. The anterior horn from the level of interventricular foramen to the frontal lobe. The inferior horn lies in the temporal lobe. The posterior horn extends to the occipital lobe. The posterior and anterior horns are lacking choroid plexus. The central part and the inferior horn have got the choroid plexuses since the choroid fissure is confined to this part of the lateral ventricles. The choroid plexus produce the cerebrospinal fluid. The volume of the lateral ventricles increase with age.
2. THIRD VENTRICLE
The third ventricles connect to the lateral ventricle by foramen of monro. The third ventricle is located in between the right and left thalamus. Its boundaries are as follow;
-The roof is formed by the ependymal layer stretching across the two thalami.
-The lamina terminalis which stretches between the optic chiasma and the rostrum of the corpus callosum forms the anterior wall.
-The lateral wall is formed by the medial border of the thalamus and the hypothalamus.
-The floor is formed by the thalamic structures.
-The posterior wall is formed consists of pineal body, posterior commissure, habenular commissure and cerebral aqueduct.
The anterior surface of the ventricles contains the following protrusions:
• Supra-optic recess _ it is located above the optic chiasm of the optic nerves.
• Infundibular recess – it is located above the optic stalk of the optic nerves.
• Pineal recess_ projects into the stalk of the pineal gland.
3. FOURTH VENTRICLE
It is the last in the ventricular system. It receives the cerebrospinal fluid from the third ventricle via the central aqueduct. It lies between the pons and medulla oblongata and anterior/ ventral to the cerebellum. It extends from the central aqueduct superiorly to the central canal of the brainstem and medulla oblongata inferiorly. It has the following boundaries;
-lateral walls are formed by cerebellar peduncles, gracile and cuneate tubercles.
-floor formed by the rhomboid fossa.
-Roof formed by the cerebellum.
CSF is a clear watery fluid containing nutrients, sodium chloride, potassium, glucose and some proteins. It fills the ventricles of the brain and the spinal cord. It is secreted by the choroid plexus in the ventricles and extends into the subarachnoid space. Its drainage occurs in the subarachnoid cisterns, then to the dural venous sinuses.
-provides nutrients to the brain.
– protects the brain and spinal cord from trauma.
-removes waste products from cerebral metabolism.
1. Clinical anatomy for students (problem solving approach) Neeta v Kulkarni.
2. Moore clinically orientated anatomy- Keith L Moore, Arthur f Dalley, Anne M.R Agur
3. Www. Wikipedia. Org