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It is hypothesized that in the “more highly evolved” mammals, including the domesticated mammals, that the brainstem and the cerebellum receive arterial blood through the vertebrobasilar system whilst the internal carotid arteries primarily supply the forebrain. In camels, the arterial blood supply to the brain differs from that of ruminants since the internal carotid artery and the rostral epidural rete mirabile (RERM) are both present and the basilar artery contributes a significant proportion of cerebral afferent blood. In this study, we described the anatomical distribution of the vertebrobasilar system arterial supply in the dromedary. Secondly, we determined the direction of blood flow within the vertebral and basilar arteries using transcranial color doppler ultrasonography. Thirdly, we quantified the percentage arterial contributions of the carotid and vertebrobasilar systems to the dromedary brain. Fifty-five heads of freshly slaughtered male Omani dromedaries aged 2–6 years were dissected to determine the distribution and topography of the arterial distribution to the brain. Their anatomical orientation was assessed by casting techniques using epoxy resin, polyurethane resin and latex neoprene. The epoxy resin and polyurethane resin casts of the head and neck arteries were used to measure the diameter of vertebrobasilar arterial system and carotid arterial system at pre-determined locations. These arterial diameters were used to calculate the percentage of blood supplied by each arterial system. The vertebrobasilar system in dromedary camels consists of paired vertebral arteries that contribute to the ventral spinal artery and basilar artery at multiple locations. In most specimens the vertebral artery was the primary contributor to the basilar artery compared to that of the ventral spinal artery. In four specimens the ventral spinal arteries appear to be the dominant contributor to the basilar artery. Transcranial color doppler ultrasonography confirmed that the direction of blood flow within the vertebral and basilar arteries was toward the brain in animals examined in ventral recumbency and when standing. The vertebrobasilar system contributes 34% of the blood supply to the brain. The vertebrobasilar system is the exclusive supply to the medulla oblongata, pons and cerebellum.

We studied the arterial circle in the brain of five specimens of the Alouatta belzebul primate. The material had the arterial system perfused (water at 40°C), injected with stained latex (Neoprene 650), fixed in aqueous formaldehyde solution (10%) and dissected for vessel verification. The arterial circle of this primate is composed of two vascular systems: the vertebra-basilar and the carotid ones, which anastomose to close the arterial circuit. In the caudal portion of the arterial circle, there are the vertebral arteries and their branches: the rostral spinal artery and the caudal inferior cerebellar artery. The anastomosis of the vertebral arteries gives rise to the basilar artery. It presented an anatomical variation at the beginning of its path, forming a double basilar artery, called arterial island. In its course, it emitted branches giving rise to the rostral inferior cerebellar artery, the pontine arteries, the rostral cerebellar arteries, the satellite rostral cerebellar arteries and its terminal branch, the caudal cerebral artery, which presented itself in two segments: the pre-communicating one and post-communicating, joining the internal carotid artery and originating the caudal communicating artery. This group of arteries and anastomoses enclose the caudal portion of the arterial circle. From the right and left internal carotid arteries begins the rostral portion of the arterial circle, which consists of the right and left rostral cerebral arteries and the right and left middle cerebral arteries. The rostral cerebral arteries anastomose into a single trunk, giving rise to the interhemispheric artery, and in A. belzebul and Sapajus libidinosus, the rostral communicating artery is absent. The interhemispheric artery goes to the midbrain region and the corpus callosum knee divides into pericalous artery and callosarginal artery, which will supply the pre and post-central regions of the cerebral hemispheres of this species, as well as other non-human and human primates. It is noted that in the first part of the left rostral cerebral artery, there is a direct inosculation between the recurrent branch of the rostral cerebral artery and left middle cerebral artery to supply the entorhinal region. This fact also occurs in Pongo spp. The middle cerebral artery travels along the lateral sulcus where it emits several superficial branches to irrigate the superior and inferior lateral cortical regions of the frontal, parietal and temporal lobes. It is not part of the arterial circle but is the terminal branch of the internal carotid artery. A. belzebul can be considered to depend on two sources of supply to the brain: the vertebra-basilar and carotid systems, contributing to the intervention of veterinarians during clinical and surgical procedures in other primates, as well as the preservation of wild animals. RESUMO: Estudamos o círculo arterial no encéfalo de cinco espécimes do primata Alouatta belzebul. O material teve o sistema arterial perfundido (água a 40°C), injetado com látex corado (Neoprene 650), fixado em solução aquosa de formaldeído (10%) e dissecado para verificação dos vasos. O círculo arterial deste primata é composto por dois sistemas vasculares: vértebro-basilar e o sistema carotídeo, que se anastomosam para fechar o circuito arterial. Na porção caudal do círculo arterial encontra-se as artérias vertebrais e seus ramos: artéria espinal rostral e a cerebelar inferior caudal. A anastomose das artérias vertebrais dá origem a artéria basilar. Esta apresentou uma variação anatômica no início do seu trajeto, formando uma dupla artéria basilar, denominada ilha arterial. Em seu trajeto emitiu ramos dando origem a artéria cerebelar inferior rostral, as artérias pontinas, as artérias cerebelares rostrais, as artérias cerebelares rostrais satélites e o seu ramo terminal, a artéria cerebral caudal, que apresentou-se em dois segmentos: o pré-comunicante e pós-comunicante, unindo-se a artéria carótida interna e originando a artéria comunicante caudal. Este grupo de artérias e anastomoses encerram a porção caudal do círculo arterial. Das artérias carótidas internas direita e esquerda, inicia-se a porção rostral do círculo arterial, ao qual é constituído pelas artérias cerebrais rostrais direita e esquerda e as artérias cerebrais médias direita e esquerda. As artérias cerebrais rostrais se anastomosam em um tronco único dando origem a artéria inter-hemisférica e em A. belzebul e Sapajus libidinosus, a artéria comunicante rostral se encontra ausente. A artéria inter-hemisférica segue para região média do encéfalo e no joelho do corpo caloso se divide em artéria pericalosa e artéria calosomarginal, que vão suprir as regiões pré e pós-central dos hemisférios cerebrais desta espécie, assim como outros primatas não humanos e humano. Nota-se que na primeira parte da artéria cerebral rostral esquerda, ocorre uma inosculação direta entre o ramo recorrente da artéria cerebral rostral e artéria cerebral média esquerda para suprir a região entorrinal, esse fato também ocorre em Pongo spp. A artéria cerebral média segue seu trajeto pelo sulco lateral onde emite vários ramos superficiais para irrigar as regiões corticais supero e ínfero lateral do lobo frontal, parietal e temporal, esta não faz parte do círculo arterial mas é o ramo terminal da artéria carótida interna. Pode-se considerar que A. belzebul depende de duas fontes de suprimento para o encéfalo: os sistemas vértebro-basilar e carotídeo, contribuindo na intervenção de médicos veterinários durante os procedimentos clínicos e cirúrgicos em outros primatas, assim como na preservação de animais silvestres.

Estudamos em trinta espécimes do primata Cebus apella sp. (Linnaeus, 1766) o sistema carótico do encéfalo em animais coletados dentro dos parâmetros internacionais de bioética e bem estar animal. O material teve o sistema arterial perfundido (água a 40 °C), injetado com látex corado (Neoprene 450, Dupont® do Brasil e Sulvinil® Corante, Glassurit), fixado em solução aquosa de Formaldeído (10%) dissecado sob lupa (RASOR - II - 20) para sistematização dos vasos. O sistema carotico é composto pela porção intracraniana e intradural dos seguimentos dependentes das artérias carótidas internas esquerda e direita, as artérias carótidas do encéfalo (ace) e seus ramos de divisões látero-mediais e ântero-mediais: as artérias cerebrais médias acm e rostrais (acr), comunicantes caudais e artérias corioídeas Está interligado, através das artérias comunicantes caudais, ao sistema vértebro-basilar (100%). A ace termina trifurcando-se (50%), ou bifurcando-se (50%) em arranjos vasculares que envolvem as acm e acr, acc e artéria corioídea. A acm é o ramo mais estável deste circuito e a acr após vascularizar os bulbos olfatórios (93,3%) anastomosa-se com a artéria contralateral formando a artéria inter-hemisférica que conecta rostralmente os leitos sanguíneos do circuito arterial da base do encéfalo. Pode-se considerar que o Cebus apella sp. depende de duas fontes de suprimento para o encéfalo: os sistemas basilar e carotídico, isto indica um grau elevado de maturidade evolutiva. A ausência de anomalias demonstra neste primata estabilidade evolutiva. The carotid system of the encephalon of thirty species of the primate Cebus apella sp. (Linnaeus, 1766) was studied in this research. The material was collected according to international bioethics parameters and animals' welfare. The arterial system was perfused (water at 40 °C), injected with colored latex (Neoprene 450, Dupont® do Brasil and Sulvinil® coloring, Glassurit), fixed in formaldehyde aqueous solution (10%) and dissected under magnifying glass (RASOR, II-20) for the systematization of vessels. The carotid system is composed by the intracranial and internal portions of both right and left carotid arteries, the carotid arteries of the encephalon and their lateromedial and anteromedial branch divisions: the medial and rostral cerebral arteries, communicating caudal and interconnected arteries. It is interconnected through the caudal communicating arteries to the vertebral-basilar system (100%). The internal carotid artery ends up being divided into three: caudal communicating arteries, medial cerebral and rostral cerebral (50%) or into two: medial cerebral and rostral cerebral arteries (50%). The medial cerebral artery is the most stable branch of this circuit. and after ventricularizing the olfactory bulbs (93.3%), the rostral cerebral artery becomes anastomosis with the contralateral artery, forming the interhemispheric artery that connects the blood layers of the arterial circuit of the encephalon base. It can be considered that Cebus apella sp. depends on two supply sources to the encephalon: the basilar and carotid systems, what indicates an important degree of evolutionary maturity. The absence of anomalies in this primate demonstrates evolutionary stability.