The morphology and incidence of supraependymal structures in the cerebral ventricle system in sheep

The morphology and distribution of supraependymal structures in the ventricular system of sheep of both sexes were studied by common histological methods. Seven forms of supraependymal structures were distinguished according to shape; they are most frequent and most variable in the infundibular region of the third cerebral ventricle. In the ewes their occurrence in this region depends on the status of the ovarian cycle and in the rams it depends on the year season. The most frequent forms are hemi-spherical to spherical light-coloured protrusions and the so-called blebs: in the ewes they occur during anoestrus and, to a minor extent, during proestrus, and in rams in the "rest" period. In the winter reason (the rest period) the rams have button-like formations on ependyma surface in the infundibular region, and in summer there are finger-like protrusions. No such structures occur in the ewes. A larger part of the supraependymal structures are believed to be products of ependyma secretion which, in the infundibular region but nowhere else, is associated with sex: with the ovarian cycle in the ewes and with the year season in the rams.