Anatomy of the Auditory Tube

Abstract

The musculotubar canal opens on the undersurface of the skull posteromedial to the foramen spinosum, and directly behind that aperture in children. The end of the bony part of the auditory tube and the lower part of the tensor tympani occur in that area. It should be noted that fibers always pass between the tensor tympani and the tensor veli palatini (both of which are supplied by the trigeminal nerve). The upper canal for the tensor tympani and the lower canal for the auditory tube are separated by a septum which is often perforated. The bony part of the auditory tube is 11–12 mm long in our adult material and forms a 50° angle (42–57°) with the midsagittal plane. The cartilaginous part of the auditory tube is usually 24–25 mm long in adults. It runs medially downward, forming an angle of 34.6° (14–47°) with the FHP (Pahnke and von Lüdinghausen 1989) and an angle of 43.6° (32–52°) with the median plane. This places the pharyngeal opening of the tube about 15 mm below the plane of its tympanic opening. In children, the downward slope of the auditory tube is somewhat less pronounced than in adults (about 10°) prior to eruption of the permanent teeth. The tube is angled about 5° anteroinferiorly at the junction of its bony and cartilaginous parts (the “isthmus” of the auditory tube). Behind the inferior tegmental process is the petrotympanic fissure which transmits the chorda tympani to the lingual nerve and the anterior tympanic artery to the middle ear.