Topographical anatomy of dog's middle and inner ears.

摘要

The topographical anatomy of domestic animals, including that of dogs, has been insufficiently described in current literature. The present study aimed to systematically measure and anatomically describe the temporal bones of dogs by dissecting 12 specimens (24 temporal bones). It is noted that the air spaces in the temporal bones are well developed and form a pneumatic system filled with air from the Eustachian tube. The largest part of this system is the tympanic bulla which is situated superficially and is an important landmark facilitating the surgery of the middle ear. After opening the tympanic bulla, the promontory is clearly visible as well as all auditory ossicles and tendons of the intrinsic muscles. The study also reveals that the middle ear has several bony recesses, penetrating the majority of the walls of the tympanic cavity and created almost complete separate compartments. One of these compartments is an air cell situated beneath the facial canal - posterior to the promontory. The facial nerve on this segment is deprived of its bony sheath, and is the possible entrance of bacteria in otitis media. Additionally, the proximity of the middle ear with other structures of the skull is also important: the epitympanic recess of the middle ear is close to the venous temporal canal, and the region of the orifice of the Eustachian tube is close to the internal carotid artery canal. The semicircular canals are of considerable size, the biggest one being the superior canal and the smallest the posterior canal. Only 4, not 5 openings of semicircular canals in the vestibules are studied because the two of them possess common side paths in the bony labyrinth. From the parameters measured, the most stable are vestibule size (2x3 mm), and the most variable - cochlea (5.85-7.4 mm of height) and tympanic cavity (14.2-22.6 mm of length). However, none of the studied parameters are significantly correlated with skull length..