OPENING OF THE AUDITORY TUBE IN HORSES - ANATOMICAL BASICS AND ENDOSCOPIC FINDINGS

The structures of the auditory tube in horses were investigated in res pect to the opening mechanism. Macroscopic preparation techniques were used and the results were compared with the findings of endoscopical inspection of the nasopharynx. As for macroscopic anatomy the shape an d the position of the cartilage of the auditory tube as well as its su rrounding mucous membrane are presented. Close to the pharyngeal orifi ce ol the auditory tube, the mucous membrane forms a distinct plica, w hich is functionally important, but until now only sparsely documented . Further the position and the course of the adjoining M. tensor veli palatini, M. levator veil palatini, Mm. pterygo- and palatopharyngeus are demonstrated. The endoscopical investigation indicates that - with regard to the opening mechanism of the auditory tube - the M. pterygo pharyngeus is the main actor: muscle contraction causes the large cart ilage flap to bend and thus the pharyngeal orifice is widened. In the initial phase, the M. tensor veli palatini and M. levator veli palatin i assist in this process.