» The Larynx
The larynx is largely situated between the mandibular rami but extends into the upper part of the neck, where it may be felt. The appreciation of its palpable features requires the correct identification of three midline skeletal structures: the basihyoid and the thyroid and cricoid cartilages.
Those familiar with the surface anatomy of the horse may experience an initial uncertainty when first examining cattle. The different spacing of the ventral prominences is due to the shape of the bovine thyroid cartilage, which is complete ventrally and most salient toward its caudoventral point.The bovine larynx shows few other peculiarities of note. The entrance, which may be inspected with the assistance of a laryngoscope, is bounded by the low, curled margin of the epiglottis and the prominent corniculate extensions of the arytenoid cartilages (Fig. 25.9/15 and 16). Intubation is made difficult by a slight caudal deflection of the entrance (see Fig. 25.9).
The vestibule possesses neither median nor lateral ventricles, and its side walls shelve smoothly to the glottis. The size of the glottic cleft varies with the phase of respiration, but the changes are not pronounced during quiet breathing. It is narrower than might be supposed, and this limits the caliber of the endotracheal tube that may be passed. The relationship to the medial retropharyngeal lymph nodes is important; when much enlarged, these may seriously compress the larynx as well as the pharynx (Fig. 25.9/18).