![]() ![]() Tracheal smooth muscles lie in the dorsal tracheal membrane. (Modified with permission from Collin B: Atlas d’anatomie, Liege, Belgium, 1976, Universite de Uege.) In some parts of the world, this dysfunction is called “choking down.”įIGURE 9-3 Cross-sectional view of the cervical trachea (l: tracheal muscle 2: cartilage 3: adventice 4: mucosa 5: connective tissue). It induces a narrowing of the upper airways and causes a soft palate flapping, sometimes resulting in a dramatic asphyxia in racing horses. ![]() In all other conditions, this dorsal displacement is abnormal and will induce dyspnea, especially during strenuous exercise. In horses, the displacement of the caudal border of the soft palate to a position above the epiglottis, called dorsal displacement of the soft palate, is not physiologic, except when it occurs during swallowing, coughing, or whinnying (see Figure 9-1). (l: nasal cavity 2: nasopharynx 3: oropharynx 4: soft palate 5: intrapharyngeal ostium (“button hole”) 6: epiglottis 7: corniculate cartilage 8: larynx 9: trachea 10: guttural pouch 11: frontal sinus 12: sphenopalatine sinus 13: esophagus 14: tongue 15: food bolus 16: closed larynx 17: endoscope.) (Modified with permission from Cook WR: Specifications for speed in the racehorse: in the airflow factors, Menasha, WI, 1989, Russell Meerdink.) FIGURE 9-1 Lateral view of the pharyngolaryngeal area during ( A) normal breathing, ( B) swallowing, and ( C) dorsal displacement of the soft palate.
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