[Electron microscopic observation of ependyma (author's transl)]

The fine structure of the normal ependymal cell has been described. The ependymal cells form a closely knit single layer lining the ventricles. They are bordered on one side by the ventricular lumen and by the neuropil on the basal surface. The luminal surface is characterized by microvilli and cilia. The former differ from those seen in the respiratory tract or intestine in that they have a smooth surface and are devoid of a coating material. They differ from the microvilli of the choroid plexus by being straight and relatively stubby. The cilia appear indistinguishable from those seen on other cells and display the usual 9+2 microtubuler structure. The apposing surfaces of adjacent ependymal cells show various junctional devices such as desmosomes and others, but apparently no true tight junction such as seen in the choroid plexus are present. The basal surface abuts directly on the neuropil usually with no intervening basement membrane. The cytoplasm contains usual organelles including fine (60-90 A) filaments and glycogen granules. The latter two structures become especially abundant under pathological conditions which elicit an ependymal response. These changes very closely resemble those seen in reactive astrocytes.