Blood vessels of the bovine chorioidea. A scanning electron microscopic study.

On corrosion casts of the bovine choroidal vessels, the vascular architecture was investigated by means of scanning and corresponding transmission electron microscopy. Complete filling of the vessels produced close-fitting replicas. Thus, based on different luminal structure, the arteries and veins in the lamina vasculosa could be easily distinguished. The branches of these vessels were followed to the choriocapillaris. The complete pattern of afferent and efferent vessels provided the opportunity to establish a scheme of choroidal microcirculation. The choriocapillaris in the bovine as a freely communicating network is subdivided into star-shaped areas of roughly hexagonal form. On the boundaries of these areas the afferent vessels (arterioles) - arranged at regular distances - join the choriocapillaris, whereas drainage of the choriocapillaris is effected by a single efferent vessel (venule) in the center of each area.