Chapter 6. EAR DISORDERS

Non scholae, sed vitae discimus. We do not learn for school, but for life.

6.1. EAR CLINICAL ANATOMY AND PHYSIOLOGY

The ear consists of three parts: external (or outer), middle and inner ear (fig. 6.1). The external and the middle ear start forming on the 5th week of

Fig. 6.1. Schematic structure of peripheral part of auditory system: 1 - tympanic cord (chorda tympani); 2 - auditory ossicles; 3 - mastoid air cells (cellula mastoidalis); 4 - tympanic cavity (cavum tympani); 5 - external auditory meatus (meatus acusticus externus); 6 - tympanic membrane (membrana tympani); 7 - internal jugular vein (v. jugularis interna); 8 - semicircular canals (canalis semicircularis); 9 - facial nerve (n. facialis); 10 - vestibulocochlear nerve (n. vestibulocochlearis); 11 - cochlea (cochlea); 12 - internal carotid artery (a. carotis interna); 13 - tensor veli palatini muscle (m. tenzor veli palatini); 14 - auditory tube (tuba auditiva); 15 - levator veli palatini (m. levator veli palatine). The external ear is shown in blue colour, middle ear - in green colour and inner ear - in yellow colour

prenatal development from first and second pharyngeal arches. By the time of birth, the fetus has a fully developed tympanic cavity with six walls. Its opening is represented by myxoid tissue, which usually dissolves after 6 months and serves a good nutrient for infections agents.

The inner ear starts forming on the 4th week of intrauterine development; by the 9th week it is already formed, however, the growth of the labyrinth is completed in general by the end of the first year of life. The inner ear is subdivided into the cochlea and the vestibule. The vestibule is phylogenetically older, while the cochlea develops at later stages.