[ anatomical and histological study of laryngeal saccule of the donkey [equus asinus]]

ABSTRACT

Although donkeys play an important role as pack and draught animals, there is sparse information available on the histological and anatomical data for their respiratory tract. This study examined the larynxes of 4 healthy donkeys to provide data using histological techniques and anatomical dissection. The histological specimens were taken after fixation in 10% formalin and tissue passages were stained with hematoxylin and eosin, and then studied under a light microscope. The laryngeal muscles and mucosa, for anatomically studying the saccules, were dissected and photographed. Compared with the horse, the donkey epiglottis is relatively shorter and more sharply pointed. Ashallow, thumb shaped depression on the rostral of each vocal fold corresponds in position to the laryngeal ventricle in the horse. In the donkey, large paired laryngeal saccules, interposed between the thyroarytenoideus M. and the thyroid cartilage, open into the laryngeal cavity through a small circular orifice. There is a pseudostratified ciliated columnar epithelium lined saccule. Sero-Mucus secreting glands, subepithelial lympho-venous plexuses and lymph follicles were present in its orifice wall. Furthermore, the large thyroarytenoideus M. is subdivided into ventricular and vocal parts, which are thought to control the expression of secretion from the laryngeal saccule. It seems that unusual characteristics of vocalization in the donkey may be related to the shape and orientation of these larynx resonance chambers. Further investigations are needed to clarify this point