Ultrastructure of the surface of the organum vasculosum laminae terminalis in different animal species.

A scanning electron microscope study was made of the surface of the organum vasculosum laminae terminalis of the rat, dog and cat. The ependyma of this organ, in all three species, is lacking in cilia or is only monociliate; it exhibits numerous supraependymal processes and cell bodies and in the different species studied there are differences that affect the number, size and distribution of the supraependymal cells. There is a great richness of vessels in the supraepedymal layer of the organum vasculosum laminae terminalis.