Baptiste K E
Department of Veterinary Internal Medicine, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada.
Vet J. 1998 Mar;155(2):139-48. doi: 10.1016/s1090-0233(98)80009-9.
The equine guttural pouch is a large, air-filled diverticulum of the auditory tube whose function is not clear. Since the horse does not possess a known, well-developed brain-cooling mechanism that could satisfy cerebral thermoregulatory demands, an hypothesis is proposed that respiratory air enters the guttural pouches, when needed, to ventilate and cool the internal carotid arteries (ICA). Experiments were initially carried out on nine cadavers, where blood flow was mimicked with warmed saline propelled by peristaltic pumps. Subsequent experiments were conducted on an anaesthetized horse where the guttural pouch was ventilated and ICA temperatures were measured. Results showed that whenever the guttural pouch was ventilated with cooled or warmed environmental air, or warmed 100% humidified air, temperatures within the ICA dropped significantly in cadavers (0.4-5 degrees C) and in the anaesthetized horse (1-3 degrees C), depending on conditions. Simulated respiration trials also resulted in ICA temperature drops of 0.9-2.3 degrees C in two of five cadavers tested, indicating that the wide 3-5 cm pharyngeal orifices of the guttural pouches have the capacity to allow enough respiratory air to ventilate the pouch. Despite the fact that a single, unbranching 13 cm portion of the ICA is exposed on the wall of each guttural pouch, the results of this investigation suggest that during heavy exercise, horses could utilize their guttural pouches to cool ICA blood destined for the brain.
马的咽鼓管囊是咽鼓管的一个充满空气的大憩室，其功能尚不清楚。由于马没有已知的、发育良好的脑冷却机制来满足大脑的体温调节需求，因此提出了一种假说，即呼吸空气在需要时进入咽鼓管囊，以对颈内动脉（ICA）进行通风和冷却。最初在9具尸体上进行了实验，用蠕动泵推动的温热盐水模拟血流。随后在一匹麻醉的马身上进行了实验，对咽鼓管囊进行通风并测量ICA温度。结果表明，无论用冷却或温热的环境空气，还是温热的100%湿度空气对咽鼓管囊进行通风，尸体（0.4 - 5摄氏度）和麻醉马（1 - 3摄氏度）体内ICA的温度都会显著下降，具体取决于条件。在测试的5具尸体中的2具上进行的模拟呼吸试验也导致ICA温度下降了0.9 - 2.3摄氏度，这表明咽鼓管囊宽3 - 5厘米的咽口有能力让足够的呼吸空气进入囊内。尽管每侧咽鼓管囊壁上都暴露着一段13厘米长、无分支的ICA，但这项研究的结果表明，在剧烈运动时，马可以利用其咽鼓管囊来冷却流向大脑的ICA血液。
