The ventricles of the brain

The ventricles

These are fluid filled cavities within the brain that represent extension of the central canal of the spinal cord into the brain and consist of four chambers that are filled with (CSF) ( liquor cerebrospinallis ).

They are lined by ependymal cells which are one type of glial cells and are responsible for choroid plexus formation which in turn responsible for CSF production. They are responsible for production, transport and removal of the CSF.

The functions of the CSF

1) Protection : act as a cushion to the brain to limit neural damage in head injuries 2) Buoyancy :The brain being immersed in the CSF and the brain weight is reduced to 25 gm and this protect the base of the brain 3) Chemical stability : a good homeostatic environment created by the CSF for proper functioning of the brain, like low extra cellular K for synaptic transmission

The ventricles

There are two one in each cerebral hemisphere and are connected to the unpaired via the interventricular foramen (foramen of Monro) and this third ventricle is connected to the forth ventricle via the (Aqueduct of Sylvius) and the CSF then flow out to the subarachnoid apace through three apertures one central called foramen of Magendie and two lateral called foramena of Lushka.

The lateral ventricles The two lateral ventricles form the largest cavities of the and each one has its own extension, the anterior horn (frontal horn) , inferior horn (temporal horn) and posterior horn (occipital horn). Important structures border the lateral ventricles are the Caudate nucleus and the thalamus. the volume of the lateral ventricles increases with age. The 3rd ventricle The two lateral ventricles are connected to the third ventricle through the interventricular foraena (foramina of Monro). It is situated between the right and left thalami, the anterior wall of the third ventricle has two protrusions: • Supra optic recess located above the • Infundibular recess located above the ptuitary stalk The 4th ventricle It is the last ventricle in the system. It receives CSF from the third ventricle via the cerebral aqueduct (acqueduct of Sylvius). It lies within the brainstem at the junction of the pons and medulla oblongata, from the forth ventricle the CSF runs into two places: • Central canal of the spinal cord • Subarachnoid cisterns via foramen of Magendie and Luschka

Production and absorption of CSF

The CSF is produced via the choroid plexus (which consists of capillaries, loose connective tissues surrounded by cuboidal epithelium) and is located in the lining of the ventricles. Plasma is filtered by the epithelial cells to produce CSF.

Then after the CSF is absorbed through the venous sinuses via an extension of the arachnoid mater as an arachnoid villous (villi) to the lumen of the sinyses especially the superior sagittal sinus.

Obstruction to the CSF pathway at any point or impaired absorption lead to abnormal accumulation of CSF with the resultant condition … hydrocephalus