Mammals possessing a carotid rete can cool arterial blood on its way to the brain in a process known as selective brain cooling. Whether mammals without a carotid rete are capable of selective brain cooling is controversial.(1-3) Baptiste et al.(4) present evidence of a mechanism for selective brain cooling in equids, a group of mammals that do not possess a carotid rete. They measured cooling of blood in the internal carotid artery as it traversed the guttural pouch and concluded that the cooling occurred as a result of heat exchange with air in the pouch. For that to be so the air entering the pouch must have the capacity to accept heat at the rate that heat is lost from the internal carotid artery. The magnitude of heat acceptance by air in the guttural pouch can be measured as the difference in enthalpy of air entering and leaving the pouch multiplied by the ventilation rate of air in the pouch. We here construct a model covering the range of possibilities for those parameters. We conclude that a heat sink of this magnitude in the pouch is highly unlikely.
|Journal||South African Journal of Science|
|Publication status||Published - 2002|