Twenty four pieces of Throughbred horses were injected with coloured solution of Neoprene latex 650, kept in formalin solution and dissected. The arteries of the encephalon basis depend on two large sources, the occipital arteries (occipito-basilar system) and the internal carotid arteries (carotid system). The basilar artery results from the fusion of the right and left occipital arteries (95.8%) or yet it is the direct continuation of the right occipital artery (4.2%). At the level of cerebral peduncles, the basilar artery bifurcates and shows a variable number of anastomotic tracts with a retiary disposition. The resulting elements of this division are two well defined terminal branches, this way named up to where the cerebral caudal artery has its origin, at both sides. It was also seen the occurrence of anastomotic tracts related to the origin (37.5%) and the course of the basilar artery (20.8%). That artery gives numerous collaterals, the arteries: caudal cerebelar (100%), carotico-basilar (54.2%), labyrinthine (12.5%) and rostral cerebelar (100%). The basilar artery decreases the basilar artery's diameter in caudo-rostral direction and forms, with the most of its collateral branches, rostral acute angles. These facts indicate that the blood flow of the basilar artery is caudo-rostral. The arrangement of the occipito-basilar system arteries is situated between the medium and last types described by TESTUT³ and corresponds to the 2 beta category of the classification proposed by TANDLER², cited by DE VRIESE¹.
Encephalon Arteries; Horses; Basilar artery
