Editing Common ostrich (section)

====Internal adaptations====
The use of [[Countercurrent exchange|countercurrent]] heat exchange with blood flow allows for regulated conservation/ elimination of heat of appendages.<ref name=zool241/> When ambient temperatures are low, [[Heterothermy|heterotherms]] will constrict their arterioles to reduce heat loss along skin surfaces.<ref name=zool241/> The reverse occurs at high ambient temperatures, arterioles [[Vasodilation|dilate]] to increase heat loss.<ref name=zool241/>
 
At [[Room temperature|ambient temperatures]] below their body temperatures ([[thermal neutral zone]] (TNZ)), common ostriches decrease body surface temperatures so that heat loss occurs only across about 10% of total surface area.<ref name=polly/> This 10% include critical areas that require blood flow to remain high to prevent freezing, such as their eyes.<ref name=polly/> Their eyes and ears tend to be the warmest regions.<ref name=polly/> It has been found that temperatures of lower appendages were no more than {{cvt|2.5|C-change}} above ambient temperature, which minimizes heat exchange between feet, toes, wings, and legs.<ref name=polly/>

Both the Gular and air sacs, being close to body temperature, are the main contributors to heat and water loss.<ref name=Schmidt-Nielsen/> Surface temperature can be affected by the rate of blood flow to a certain area and also by the surface area of the surrounding tissue.<ref name=zool241/> The ostrich reduces blood flow to the trachea to cool itself and [[Vasodilation|vasodilates]] to its blood vessels around the gular region to raise the temperature of the tissue.<ref name=Schmidt-Nielsen/> The air sacs are poorly vascularized but show an increased temperature, which aids in heat loss.<ref name=Schmidt-Nielsen/>

Common ostriches have evolved a 'selective brain cooling' mechanism as a means of thermoregulation. This modality allows the common ostrich to manage the temperature of the blood going to the brain in response to the extreme [[ambient temperature]] of the surroundings. The morphology for heat exchange occurs via [[cerebral arteries]] and the [[Ophthalmic artery|ophthalmic]] [[Blood vessel|rete]], a network of arteries originating from the [[ophthalmic artery]]. The [[Ophthalmic artery|ophthalmic]] [[Blood vessel|rete]] is [[analogous]] to the [[carotid rete]] found in mammals, as it also facilitates transfer of heat from arterial blood coming from the core to venous blood returning from the evaporative surfaces at the head.<ref name=Maloney/>

Researchers suggest that common ostriches also employ a 'selective brain warming' mechanism in response to cooler surrounding temperatures in the evenings. The brain was found to maintain a warmer temperature when compared to [[carotid]] [[arterial]] blood supply. Researchers hypothesize three mechanisms that could explain this finding:<ref name=Maloney/>
# They first suggest a possible increase in [[metabolic]] heat production within the brain tissue itself to compensate for the colder [[arterial]] blood arriving from the core.
# They also speculate that there is an overall decrease in cerebral blood flow to the brain.
# Finally, they suggest that warm venous blood [[perfusion]] at the [[Ophthalmic artery|ophthalmic]] [[Blood vessel|rete]] helps to warm the cerebral blood that supplies the [[hypothalamus]].
Further research will need to be done to find how this occurs.<ref name=Maloney/>