Brain blood supply in ruminants

Abstract

Domesticated ruminants play a key role in world livestock production, while some other ruminant species are important in the hunting economy. Non-farm species kept in zoological gardens pose a new challenge for veterinarians. In addition, cervids are increasingly often maintained under farm conditions, in which it may be necessary to undertake medical interventions. The pattern of the brain base arteries is one of specific morphological features of species from the suborder Ruminantia, including the domestic cattle, zebu, buffalos, sheep, goats, reindeer and other deer species, giraffes, musk deer and antelopes. A specific feature of the arteries of the brain base in ruminants is the presence of the arterial nasal epidural rete mirabile, and in some species also the caudal epidural rete mirabile. In addition, in these animals the extracranial segment of the internal carotid artery obliterates, and as a consequence, blood flows into the brain by an alternative route from the maxillary artery, via the vasculature of the nasal epidural rete mirabile. It is widely accepted that the retia mirabilia in the system of head arteries in mammals are the anatomical basis of the so-called selective brain cooling. Essentially, this mechanism consists in cooling the warm blood expelled from the left ventricle during the contraction of the heart, which flows to the brain, creating a vast vasculature of the rete mirabile. It is encircled by a cooler blood, returning from the nasal cavity via the cavernous sinus. Retia mirabilia located on the brain base are the main effectors of heat dissipation and protection of the brain from overheating. This mechanism fits into the very current topic of animal welfare.