Ependyma and supraependymal structures in some areas of the fourth ventricle in the rat.

The ependyma was investigated in five areas of the rat ventricle system by means of both light and electron microscopy. The columnar, cuboidal and flattened types of the ependymal cells were mainly seen. All of them were seen in the fourth ventricle, while in the aqueductus cerebri and in the central canal the flattened type of the cell was lacking. An unusual variation as to the form of the ependymal cells was found on the roof of the fourth ventricle. Three groups of intraventricular structures were found in all investigated parts of the ventricle system: supraependymal globular structures containing irregularly arranged cristae, supraependymal protrusions appearing as homogeneous contents, and nerve profiles including nerve endings and nerve axons. The morphological characteristics of the ependyma and intraventricular profiles in the fourth ventricle allow to suppose a certain role of these structures in the exchange of various materials between the CSF, ependyma and neuropile.