Baptiste K
Department of Veterinary Internal Medicine, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada.
Vet J. 1997 May;153(3):311-9. doi: 10.1016/s1090-0233(97)80065-2.
The pharyngeal orifice of the equine auditory tube has not been adequately described. Its larger size and position, further rostral within the nasopharynx compared with other species, cannot be easily explained, but could be important for the proposed brain-cooling function of the guttural pouches; however, unlike other species, it may not be the sole regulator of auditory tube aeration. A 'second orifice' (representing the final entrance to the auditory tube diverticulum) deserves recognition in performing a role in air exchange between the auditory tube, diverticulum and middle ear. The results of this investigation suggest that regular guttural pouch ventilation during resting respiration does not occur. Previous reports may reflect, at least in part, a misinterpretation of air pressure measurements within the guttural pouches and nasopharynx. Small decreases in simulated inspiratory pressure consistently caused the passive opening of both the pharyngeal orifice and pouch ostium in horse cadavers suggesting that an active counter process may exist in the live horse to maintain closure of the guttural pouch openings during rest and light exercise. Intrinsic tone of the stylopharyngeus and pterygopharyngeus muscles may be part of this active process. The investigation offers theoretical evidence that opening of the equine auditory tubes to ventilate the guttural pouch occurs in two different ways, active and passive. The active process has two stages: (1) opening of the pharyngeal orifices by simultaneous contractions of the levator and tensor veli palatini and pterygopharyngeus muscles; then (2) opening of the pouch ostia by contractions of dorsal portions of the palatopharyngeus muscles. The alternative passive route involves reduction in tone of the stylopharyngeus and pterygopharyngeus muscles accompanied by increased inspiratory pressure.
马咽鼓管的咽口尚未得到充分描述。与其他物种相比，其尺寸更大且位置更靠前，位于鼻咽部更靠前的位置，这一点难以轻易解释，但可能对喉囊的拟议脑冷却功能很重要；然而，与其他物种不同，它可能不是咽鼓管通气的唯一调节器。在咽鼓管、憩室和中耳之间的空气交换中，一个“第二开口”（代表咽鼓管憩室的最终入口）值得被认可发挥了作用。这项研究的结果表明，在静息呼吸期间，喉囊不会进行规律性通气。先前的报告可能至少部分反映了对喉囊和鼻咽部内气压测量的错误解读。在马的尸体中，模拟吸气压力的小幅下降持续导致咽口和喉囊开口的被动开放，这表明在活马中可能存在一个主动的对抗过程，以在休息和轻度运动期间维持喉囊开口的闭合。茎突咽肌和翼突咽肌的内在张力可能是这个主动过程的一部分。该研究提供了理论证据，表明马的咽鼓管打开以对喉囊进行通气有两种不同方式，主动和被动。主动过程有两个阶段：（1）通过腭帆提肌、腭帆张肌和翼突咽肌的同时收缩打开咽口；然后（2）通过腭咽肌背侧部分的收缩打开喉囊开口。另一种被动途径涉及茎突咽肌和翼突咽肌张力的降低以及吸气压力的增加。
